This guide is for anyone who made a backup, or inherited one, and now needs to put it back onto a card. It covers checking the backup file, choosing a suitable destination card, writing it correctly, and testing the result before you rely on it. It assumes you have a Windows computer, the backup file, and a destination card at least as large as the original card the backup came from.

The central warning of this guide cannot be overstated: restoring overwrites the ENTIRE destination drive. Everything on that card will be lost, including partitions you cannot see. Double-check the drive letter every time, and never restore over a card that holds data you have not backed up elsewhere, even if you are in a hurry.

Before you start

• Restoring wipes the ENTIRE destination card. If the destination card holds anything you need, copy it elsewhere first, or use a different card.
• The destination card must be at least as large as the original card. Cards sold as the same size can differ by a few megabytes, so a restore to a slightly smaller card can fail near the end.
• If the backup is compressed as a .7z or .zip file, decompress it to a plain .img file first. Win32 Disk Imager cannot write directly from a compressed archive.
• Keep the backup file safe during the restore. Do not restore from the only copy on a drive you are about to format, and do not delete the backup until the restored card has been tested.

Before you restore, confirm what the backup actually contains. Check the file name, date, and any notes you made when you created it, and confirm the file size is plausible for the original card. A backup file that is far smaller than the card it came from may be a compressed archive you forgot to decompress, or an allocated-partitions image, which is still valid but restores differently in terms of layout. Knowing which kind you have avoids confusion when the restore behaves unexpectedly.

Step by step

1. Locate and prepare the backup file

Find the .img file, and if it is compressed, decompress it with 7-Zip to a plain .img file on a drive with enough free space. Check the decompressed size against your notes or against the original card’s capacity. If the backup is on cloud storage, download it completely before you start, because a partial download that writes successfully will not boot.

2. Insert the destination card and note its letter

Insert the destination card, wait for Windows to recognise it, and note its drive letter in File Explorer. If Windows offers to format the card, choose Cancel. You are about to overwrite the card completely, so formatting first is unnecessary. If the letter you expect is missing, reseat the card or try another reader.

3. Open Win32 Disk Imager as administrator

Run Win32 Disk Imager as administrator, click the folder icon, and select your .img backup file. Confirm the Device drop-down shows the destination card’s letter, not the letter of another drive, a USB stick with data on it, or an external hard drive. This check is the most important step in the whole restore.

4. Write the backup and eject safely

Click Write, read the confirmation dialog, and confirm only if the drive letter is correct. Wait for the success message without removing the card or letting the computer sleep. When it finishes, use Safely Remove Hardware before removing the card, because Windows may still be flushing the final writes.

5. Test the restored card before relying on it

Put the restored card into its target device and boot it. Check that the system starts, the main application runs, and recent data you expect is present. If the device is a Pi, give first boot a few minutes, and check that the filesystem has the expected size. Only after this test should you consider the restore complete and the old card disposable.

6. Make a fresh backup of the restored system

Once the restored card is working, make a new Read backup of it, especially if you changed anything during recovery, such as passwords, network settings, or software versions. That fresh backup becomes your new baseline, so the next failure does not send you back to an older state. Label it with the restore date and a note that it came from a restore.

Where to keep the backup

A backup only helps if it survives the card it came from, so copy the finished .img file off the computer you flashed from. A dedicated backup drive (Sponsored) works well for large images, and you can also keep a second copy in cloud storage such as pCloud if you want an off-site copy. Label every file with the device, date, and contents before you upload it.

Frequently asked questions

Does restoring delete everything on the destination card?

Yes. Write overwrites the entire destination drive, including all partitions and files. Move anything you need off the card first, or use a different card.

Can I restore to a smaller card than the original?

No, not reliably. The destination must be at least as large as the original card, and cards sold as the same size can differ by a few megabytes, so use the same size or larger.

Do I need to decompress a .7z backup before restoring?

Yes. Decompress it back to a plain .img file with 7-Zip first, then write that file with Win32 Disk Imager, which cannot write directly from a compressed archive.

For the full set of guides, see the Tutorials hub, and get the program from the download page. Related guides include: how to back up sd card to img, compress img file 7zip, clone one sd card to many — each one covers one job in the same plain style as this guide.

This guide is for anyone who has a folder full of large .img files, or who is about to make a backup and wants a storage plan that will last. It covers installing 7-Zip, choosing a format, compressing correctly, verifying the archive, and decompressing before a restore.

One rule governs the whole guide: never delete the original .img file until you have verified the compressed archive and, ideally, tested a restore from it. Compression is reliable, but a backup you have never decompressed is a promise, not a proven copy. Keep the original until the compressed copy has earned your trust.

Before you start

• Check free disk space before compressing. You need room for both the original .img file and the archive until you verify the archive and delete the original.
• Do not compress an image while Win32 Disk Imager is still writing or reading it. Wait for the operation to finish completely.
• Use a clear archive name that matches the image name, with the date and device, so you can find the right backup months later.
• Remember that a compressed archive must be decompressed back to a plain .img file before Win32 Disk Imager can write it. Win32 Disk Imager does not write directly from a .7z or .zip archive.

Why do .img files compress so well, when they are already exact copies? Because empty sectors are highly repetitive: long runs of zeros compress to almost nothing. An image of a system that uses 4 GB on a 64 GB card is mostly empty space, so it compresses dramatically. An image of a card filled with photos, videos, or encrypted data compresses poorly, because that data is already dense or random. Both outcomes are normal, and the compression ratio tells you about the contents, not about whether you did something wrong.

Step by step

1. Install 7-Zip

Download 7-Zip from its official site, install the version matching your Windows system, and confirm it appears in the File Explorer right-click menu. You do not need any other compression tool for this guide, and you should avoid obscure tools that promise extreme ratios, because a backup format you cannot open in five years is worse than a slightly larger archive you can open anywhere.

2. Right-click the .img file and choose Add to archive

In File Explorer, right-click the .img file, choose 7-Zip, then Add to archive. This opens the compression settings dialog, where you choose the format and level. Do not simply choose Add to .zip from the quick menu if you want the best compression, because the dialog gives you control over format and level that the quick option does not.

3. Choose .7z format and a sensible level

Set Archive format to 7z and Compression level to Normal or Maximum. Normal is faster and already captures most of the saving on a sparse image; Maximum squeezes a little more at the cost of much longer compression time. For a one-off backup, Normal is the practical choice. Leave the other settings at their defaults unless you have a specific reason to change them, such as splitting the archive for storage on smaller media.

4. Compress and wait without interrupting

Click OK and wait for compression to finish. For a 64 GB image, this can take many minutes, even on a fast computer, because the tool must read the whole file. Do not put the computer to sleep, and avoid heavy disk work at the same time. When it finishes, note the archive size and compare it with the original, so you know how much you saved and whether the ratio looks plausible for the image’s contents.

5. Verify the archive before deleting the original

In 7-Zip, use Test archive on the new .7z file, or open it and confirm the .img file inside has the expected size. Only after that test passes should you consider deleting the original .img file to reclaim space. If you have room, keeping both for a while is even safer, and for irreplaceable backups, keeping the original on a separate drive is worth the space.

6. Decompress before you restore

When you need the backup, decompress the archive back to a plain .img file first, then write that file with Win32 Disk Imager as usual. Do not try to point Win32 Disk Imager at the .7z file, because it expects a raw image. After decompressing, check the file size against your notes, write it to a spare card for testing if the original is still working, and only then restore over a failed card.

Where to keep the backup

A backup only helps if it survives the card it came from, so copy the finished .img file off the computer you flashed from. A dedicated backup drive (Sponsored) works well for large images, and you can also keep a second copy in cloud storage such as pCloud if you want an off-site copy. Label every file with the device, date, and contents before you upload it.

Frequently asked questions

Can Win32 Disk Imager write a .7z file directly?

No. Decompress the archive back to a plain .img file first, then write that file with Win32 Disk Imager. The program expects a raw image, not a compressed archive.

Why did my image barely shrink when compressed?

Because the card was nearly full of dense data, such as photos, video, or encrypted files, which compress poorly. Sparse system images shrink dramatically, while full data cards do not.

Should I delete the original .img after compressing?

Only after you test the archive with 7-Zip Test archive and confirm the file inside has the expected size. For irreplaceable backups, keep the original on a separate drive as well.

For the full set of guides, see the Tutorials hub, and get the program from the download page. Related guides include: how to back up sd card to img, restore img backup to sd card, win32 disk imager allocated only read — each one covers one job in the same plain style as this guide.

This guide is for users who have made a full Read backup, been surprised by its size, and wondered whether this option is the answer. It explains the option in plain terms, shows when it produces a smaller file and when it produces the same size, and warns about the cases where a smaller image is not a faithful backup for your purpose.

The option is part of Win32 Disk Imager v1.0.0, released 2017-03-08, the current Windows-only GPLv2 release. It does not change how Write works, and it does not compress anything. It changes which sectors Read copies, and that distinction determines everything else in this guide.

Before you start

• This option affects Read only. It does not make Write faster, and it does not shrink an existing .img file you already made.
• Always keep a full backup of anything irreplaceable before you experiment with a smaller backup method. Test the smaller image by restoring it to a spare card before you rely on it.
• Understand your partition layout before you enable the option. If the card’s partitions already fill most of the card, the saving will be small, and the extra complexity may not be worth it.

To see why the option sometimes helps a lot and sometimes helps not at all, picture a 64 GB card with a 4 GB system on it and 60 GB of unallocated space. A normal Read copies all 64 GB. With Read Only Allocated Partitions, Read copies roughly the allocated partitions, so the image may be closer to 4 GB plus partition overhead. That is a large saving, and it is the case the option was designed for.

Step by step

1. Inspect the card’s partitions first

On the Pi or in a partition tool, look at how the card is divided. Note the size of each partition and how much unallocated space exists at the end of the card. If unallocated space is a large share of the card, this option is likely to help. If the partitions fill the card, expect only a small saving, and consider compression with 7-Zip instead, which shrinks empty space inside partitions as well.

2. Enable the option before you press Read

In Win32 Disk Imager, tick Read Only Allocated Partitions before starting the Read operation. The option must be set before Read begins; enabling it afterwards does not change an image you already made. Confirm the drive letter and the output file name as usual, because the rest of the Read process is unchanged.

3. Run Read and compare the output size

Click Read and wait for completion, then compare the output file size with the card’s full capacity. A much smaller file, when unallocated space was large, is the expected result. A file close to full size, when partitions fill the card, is also expected, and it does not mean the option malfunctioned. Record the size so you can compare future backups.

4. Test the smaller image by restoring it

Restore the smaller image to a spare card with Write, and boot that card in its target device. Confirm the system works and the data you care about is present. This test is essential, because a smaller image that restores correctly is a valid backup, while a smaller image you have never restored is only a hope. Never test by restoring over your only working original.

5. Decide whether to use it routinely

If the test passes and the saving is significant, you can use the option for routine backups of that card layout. If the saving is small, or if you need a bit-exact copy of the whole device for forensic or diagnostic reasons, stick with a full Read. The right choice depends on your layout and your reason for backing up, not on a general rule.

Frequently asked questions

Does Read Only Allocated Partitions compress the backup?

No. It skips unallocated space outside partitions, which makes the image smaller, but it does not compress anything. Use 7-Zip afterwards if you want further compression.

Why did my image stay large with this option enabled?

Because the card’s partitions already fill most of the card. The option skips unallocated space, not empty space inside a partition, so a full card layout gives little saving.

Is a smaller image safe to restore?

Yes, if you test it by restoring to a spare card and booting it. For normal system restores it is valid, but for forensic copies where unallocated data matters, use a full Read instead.

For the full set of guides, see the Tutorials hub, and get the program from the download page. Related guides include: how to back up sd card to img, compress img file 7zip, restore img backup to sd card — each one covers one job in the same plain style as this guide.

This guide is for anyone who has flashed a card that must work first time: a Pi going into a remote location, a card for a demonstration, a master image for cloning, or any card where a second trip to fix it would be costly. It explains what Verify Only checks, how to run it, how to read its result, and when it is worth the extra time it takes.

Verify Only exists in v1.0.0, the current Win32 Disk Imager release from 2017-03-08. The program is Windows-only and GPLv2 licensed, and Verify Only works the same way regardless of which image you wrote, whether it is Raspberry Pi OS, another Linux image, or a backup you made with Read. It compares data, not bootability, and that distinction matters for interpreting its result.

Before you start

• Verify Only reads the destination, so it does not erase anything. Still, do not remove the card during verification, because an interrupted verify gives no useful result.
• Keep the original .img file. Verify compares the card against that file, so if you delete or move the image, there is nothing to compare against.
• Verify takes roughly as long as a write, because it must read the whole card. Plan for that time when a card must be ready by a deadline.

Understanding what a match means will save you from overconfidence. A verify pass that succeeds means the card’s contents match the image file, sector by sector, for the area the image covers. It does not mean the image itself is correct for your device, that the card is healthy for long-term use, or that the Pi’s power supply is adequate. Those are separate questions, and a verify pass answers only the first one: did the write land correctly?

Step by step

1. Write the image normally first

Flash the card with Win32 Disk Imager as usual: select the .img file, double-check the drive letter, click Write, and wait for success. Verify Only is a separate step after writing, not a replacement for writing. If you run Verify Only on a blank or unrelated card, it will report a mismatch, which tells you nothing except that the card does not contain that image.

2. Select the same image and the same device

Leave the Image File field pointing at the same .img file you just wrote, and leave the Device drop-down on the same drive letter. Verify compares exactly those two things, so selecting a different image or a different card invalidates the comparison. If you ejected the card after writing, reinsert it and confirm the letter again, because drive letters can change when devices are reconnected.

3. Run Verify Only and wait

Click Verify Only and wait for the process to complete without removing the card or letting the computer sleep. The progress bar advances as the card is read and compared. A full verify of a large card takes minutes, and interrupting it forces you to start again. Use that time to prepare the target device, rather than starting another disk-heavy task on the same computer.

4. Read the result correctly

A success message means the card matches the image. A failure message means it does not, and you should reflash the card, preferably after trying a different reader or USB port. If the same card fails verification twice, set it aside and test a different card, because repeated verify failures are a strong sign of failing flash or a faulty reader, not of bad luck.

5. Boot-test after a successful verify

Even after a successful verify, boot the card in its target device before you rely on it, especially for a remote deployment. Verify proves the data matches; booting proves the device can use it. The two tests together give you confidence that neither the write nor the device configuration is at fault.

Frequently asked questions

Does Verify Only change or repair the card?

No. It only reads the card and compares it with the image file. It does not write, repair, or change anything on the card.

Is Verify Only the same as writing again?

No. Writing copies the image to the card; verifying reads the card back and checks it against the image. Verify is a check, not a second write.

Should I verify every card I flash?

Verify when failure would be costly, such as a remote Pi or a master image for cloning. For quick desk tests, a boot test alone is usually enough.

For the full set of guides, see the Tutorials hub, and get the program from the download page. Related guides include: how to use win32 disk imager, clone one sd card to many, how to back up sd card to img — each one covers one job in the same plain style as this guide.

This guide is for teachers, makers, and small teams who need five, twenty, or fifty identical cards. It assumes you have a Windows computer, a reliable card reader, and enough cards of the same nominal size. It also assumes you understand the one rule that governs the whole job: writing an image wipes the destination completely, so a card you clone over is gone, not merged.

Win32 Disk Imager is well suited to this job because its Read and Write operations are exact and repeatable. It has no built-in multi-card queue, so you will write cards one at a time, but the process is fast enough for small batches, and the master image can be reused indefinitely once it is verified. For very large batches, dedicated duplicator hardware is faster, but for most classroom and workshop needs, this method is sufficient.

Before you start

• Writing wipes the ENTIRE destination card. Label your master card clearly and keep it separate from blank cards, so you never accidentally overwrite the master.
• Use cards of the same nominal size, and test that the master image fits on every batch. Cards sold as the same size can differ by a few megabytes, and a slightly smaller card will fail at the end of a write.
• Work with one card at a time. Win32 Disk Imager writes to one selected device, and trying to rush by swapping cards mid-write causes failures.
• Keep a written checklist of which cards are done. It is easy to lose track after the tenth identical card, and a half-finished batch is worse than a slow one.

Start by preparing the master card properly, because every clone inherits both its strengths and its mistakes. Install the system, configure it, update it, test it in the target device, and only then make the master image. Remove personal credentials, Wi-Fi passwords you do not want on every card, and any files that belong to one user rather than to the whole batch. A master image is a snapshot, so clean it before you copy it.

Step by step

1. Prepare and test the master card

Set up one card completely in its target device: operating system, software, settings, and test data. Boot it, run the main application, and confirm everything works. Fix any problems now, because fixing them on fifty clones is fifty times the work. When the master is ready, shut the device down cleanly and remove the card.

2. Make the master image with Read

On Windows, run Win32 Disk Imager as administrator, select the master card’s drive letter, choose an output file name for the master image, and click Read. Read copies the whole card sector by sector, so the file will be as large as the full card. Wait for success, then check the file size. Do not skip this step by writing directly from card to card, because Win32 Disk Imager does not copy card to card in one step.

3. Verify the master image on a test card

Write the master image to a spare card, boot that card in the target device, and confirm it works exactly like the master. This test card is your proof that the image is good. If it fails, fix the master and repeat, before you write to the whole batch. A bad master image multiplied by fifty cards is a costly mistake.

4. Write the image to each destination card

For each blank card, insert it, confirm its drive letter in File Explorer and in Win32 Disk Imager, click the folder icon to select the master image, and click Write. Confirm the drive letter every single time, even when you are sure, because a tired operator is the most common cause of overwriting the wrong drive. Eject each card cleanly before removing it.

5. Spot-check cards from the batch

Do not assume every card is good because the first three were. Boot a sample from the start, middle, and end of the batch in a target device, and check that the system starts and the main application runs. If a card fails, reflash it once; if it fails twice, set it aside as a suspect card rather than forcing it into service.

6. Label and store the finished cards

Label each finished card with the image name and date, using a method that survives handling, such as a small sticker or a labelled case. Store the master image with a note of which device, software versions, and settings it contains. That note is what makes the batch reproducible next term, when nobody remembers exactly what was on the master.

Frequently asked questions

Can Win32 Disk Imager copy directly from one card to another?

No. First use Read to save the master card as an .img file, then use Write to copy that image to each destination card. The image file is the middle step.

Why does a clone fail on a card sold as the same size?

Cards sold as the same size can differ by a few megabytes in true capacity. If the destination is even slightly smaller than the master card, the write can fail near the end.

Should I verify every cloned card?

Boot-test a sample from across the batch, and reflash any card that fails. Testing every card is ideal for critical deployments, while sampling is reasonable for a classroom batch.

For the full set of guides, see the Tutorials hub, and get the program from the download page. Related guides include: how to back up sd card to img, how to use win32 disk imager, flash raspberry pi os win32 disk imager — each one covers one job in the same plain style as this guide.

This guide is for anyone who flashed a Raspberry Pi image, or another Linux-based image, and now sees a card that reports far less space than its label promises. It explains why the card looks small, how Raspberry Pi OS handles expansion automatically, and what to do when expansion does not happen on its own. It also explains the Windows case, where the answer is different, so you do not chase a Linux solution for a Windows problem.

A warning first: expanding a filesystem changes partition boundaries, so back up anything important on the card before you resize it. The operation is routine and usually safe, but a power loss during a resize can corrupt the filesystem. Work on a copy if the card holds irreplaceable data, and never resize a card while the device using it is running from that card unless the tool you are using is designed for online expansion.

Before you start

• Back up the card with Win32 Disk Imager Read before resizing, if the data matters. A resize is low-risk, but a backup makes it no-risk.
• Do not expand a partition into space that belongs to another partition. Check the layout first, in the Pi itself or in a partition tool, so you know what is free and what is already used.
• On Windows, do not expect to expand a Linux ext4 partition with Disk Management. Windows cannot read ext4, so it will show the partition as unknown, and that is normal, not a fault to fix in Windows.

Understanding the layout helps everything else make sense. A typical Pi image has a small FAT boot partition that Windows can see, and a larger Linux root partition that Windows cannot read. After flashing, Windows shows the boot partition’s size and hides the rest, which is why a 64 GB card can appear as a 256 MB drive. The space is not lost; it is in partitions Windows does not display, plus unallocated space the image never assigned.

Step by step

1. Check whether expansion already happened

Boot the Pi, open a terminal, and run df -h to see the size of the root filesystem. If the root partition is close to the card’s full capacity, expansion already happened and you do not need to do anything. If it is close to the original image size, for example 2 GB on a 32 GB card, then manual expansion is needed. Checking first avoids resizing a filesystem that is already correct.

2. Use raspi-config on Raspberry Pi OS

On Raspberry Pi OS, run sudo raspi-config, choose Advanced Options, then Expand Filesystem, and reboot when prompted. This is the supported method, and it handles the partition and filesystem resize together. After rebooting, run df -h again to confirm the root filesystem now fills the card. If raspi-config reports that the filesystem is already expanded, trust that result and look elsewhere for your missing space.

3. Expand manually with a partition tool if needed

For images without raspi-config, boot the Pi from a different card, or use a Linux system, and resize with a partition tool such as GParted. Select the card, resize the root partition into the free space, apply, and then check the filesystem. Do not resize the boot partition unless you have a specific reason, and do not move the start of a partition, because moving a partition start is slower and riskier than extending its end.

4. If you only use Windows, use a Linux live system

Windows Disk Management cannot expand an ext4 partition, and third-party Windows tools that claim to do so should be used cautiously and only after a backup. The reliable route is a Linux live USB, GParted, or a second Pi booted from another card. That sounds like extra work, but it is safer than a Windows tool silently mishandling a filesystem it cannot read.

5. Verify the result and test the card

After expansion, boot the Pi from the resized card and confirm with df -h that the space is available. Copy a test file, reboot, and confirm the system still boots cleanly. If the Pi fails to boot after a resize, restore your Read backup to a spare card and retry the resize, because a failed resize is easier to recover from with a backup than without one.

Frequently asked questions

Why does my 64 GB card show only a few hundred megabytes in Windows?

Windows shows only the small FAT boot partition it can read. The Linux partitions and unallocated space are hidden from File Explorer, but they are still on the card.

Does Raspberry Pi OS expand automatically?

Yes, normally on first boot it expands its root filesystem to fill the card and may reboot once. Manual expansion is only needed if that step did not happen.

Can I expand the filesystem in Windows Disk Management?

Not for a Linux ext4 partition. Windows cannot read ext4, so use raspi-config on the Pi, or GParted from a Linux system, after backing up the card.

For the full set of guides, see the Tutorials hub, and get the program from the download page. Related guides include: flash raspberry pi os win32 disk imager, raspberry pi wont boot after flashing, how to back up sd card to img — each one covers one job in the same plain style as this guide.

This checklist is for anyone who has just flashed a card with Win32 Disk Imager, or any other tool, and now gets no boot, a rainbow screen that never moves, a kernel panic, or repeated reboots. It assumes you have a Windows computer for reflashing, a spare card if possible, and the official power supply or a known-good equivalent. Each step tells you what to check, what the result means, and what to try next.

Before you start, remember what a successful flash does and does not prove. Win32 Disk Imager reporting success proves the image was written to the card, not that the card is good, the image matches your Pi model, or the Pi is receiving enough power.

Before you start

• Do not reflash the same card repeatedly without changing anything else. If three reflashes give the same result, the problem is probably not the flash step.
• Write down what you see: LED behaviour, screen contents, and any error text. Those details are what separate a power problem from a card problem.
• Keep the original .img file. If you delete it and the download was the problem, you will have to download it again before you can test anything.

Work through the checklist in order, and stop as soon as the Pi boots. The order matters because power and card seating are faster to test than a full re-download and reflash, and because a display problem can look exactly like a boot failure. If you skip ahead to reflashing, you may fix nothing and conclude, wrongly, that the Pi itself is broken.

Step by step

1. Check power first

Use the official power supply for your Pi model, or a supply that meets its voltage and current requirements, and plug it directly into a wall outlet rather than a computer USB port or a cheap hub. A Pi that browns out under load can show a rainbow screen, reboot in a loop, or corrupt its card, and the low-voltage warning icon, a lightning bolt on newer models, is a direct sign of this problem. If you have another supply, swap it before you touch the card.

2. Reseat the card and check the slot

Power off, remove the microSD card, inspect it for dirt or damage, reinsert it firmly until it clicks or seats fully, and power on again. MicroSD slots are a common failure point, especially on Pis that have been handled often. If the card feels loose or the Pi only boots when you press the card, try a different card, because a worn slot or a slightly thin card can cause intermittent contact that looks like a software fault.

3. Try a different card with the same image

Flash the same .img file onto a different, known-good card and test it. If the second card boots, the first card is the problem, even if it worked in a camera or a phone. If the second card also fails, the image, the Pi, or the power supply is the problem, and you have saved yourself from buying cards at random.

4. Reflash carefully and verify the download

Re-download or re-decompress the image, check its size against the download page, and reflash with Win32 Disk Imager as administrator, double-checking the drive letter. A truncated download or a failed decompression can produce an image that writes without error but never boots. If Win32 Disk Imager offers a verify pass, run it, because a verify failure points directly at the card or reader rather than at the Pi.

5. Check the display and HDMI setup

Try a different HDMI cable, a different display or television, and, on models with two HDMI ports, the other port. If the green activity LED flickers normally but the screen stays blank, the Pi may actually be booting and the problem may be display detection, which is far easier to fix than a dead board.

6. Read the LEDs and any error text

Watch the LEDs during power-on. A steady red power LED with no green activity usually means the Pi cannot read the bootloader from the card. Green flicker followed by an error on screen, such as a kernel panic, means the bootloader ran but the system failed later, which points at the image or the card contents rather than at power or seating.

7. Consider the bootloader and model match

Confirm the image supports your Pi model. An image built for an older Pi may not boot on a Pi 5, and a very old image may lack the firmware a newer board needs. If you are using a Pi 4 or Pi 5 and an old image, download the current Raspberry Pi OS release and test it. For persistent bootloader problems, the Raspberry Pi documentation covers bootloader recovery, but that step is only worth taking after power, card, image, and display have been ruled out.

Frequently asked questions

My Pi shows a rainbow screen and stops. What does that mean?

A stuck rainbow screen usually means the Pi cannot proceed past the bootloader, often because of power, card seating, or a card the Pi cannot read. Work through power, reseating, and a different card before reflashing.

Win32 Disk Imager said the write succeeded, so why will the Pi not boot?

A successful write only proves the image was copied to the card. It does not prove the card is good, the image matches your Pi model, or the Pi has enough power. Test those separately.

Should I reflash first when a Pi will not boot?

No. Check power, reseat the card, and try a different display first, because those tests are faster and often reveal the cause. Reflash only after the quick checks, or with a different card.

For the full set of guides, see the Tutorials hub, and get the program from the download page. Related guides include: flash raspberry pi os win32 disk imager, how to use win32 disk imager, expand filesystem after flashing — each one covers one job in the same plain style as this guide.

This guide is for first-time Pi owners and for anyone returning to Win32 Disk Imager after using another flashing tool. It covers choosing the right Raspberry Pi OS image, writing it correctly, and getting through first boot. If you are comparing tools, the comparison guides explain where Win32 Disk Imager fits next to Raspberry Pi Imager and balenaEtcher, but if you already have an .img file and a Windows computer, this guide is all you need.

Win32 Disk Imager is Windows-only and GPLv2 licensed, with v1.0.0 released on 2017-03-08. It remains useful for Pi images precisely because it does one job without extra layers: it writes the raw image to the card, sector by sector. That simplicity also means it will not download the OS for you, verify the download automatically, or customise the image with Wi-Fi settings the way Raspberry Pi Imager can.

Before you start

• Writing the image wipes the ENTIRE destination card. Move any photos or files off the card first, and double-check the drive letter against File Explorer.
• Download Raspberry Pi OS only from the official Raspberry Pi source or a mirror you trust. A modified image can contain anything, and Win32 Disk Imager will faithfully write whatever you give it.
• Use a card of at least the size recommended for the image you chose, and prefer a reputable card from a known seller. Counterfeit cards are a leading cause of Pi problems that look like software faults.
• Use the official Pi power supply or a supply that meets the Pi model’s requirements. An underpowered Pi can fail to boot, corrupt its card, or reboot under load, even with a perfect flash.

Choose your image before you open Win32 Disk Imager. Raspberry Pi OS comes in a full desktop version, a desktop version without recommended software, and a Lite version without a desktop. For a first Pi, the desktop version is the friendliest choice. For a headless server, Lite is smaller and faster.

Step by step

1. Download and decompress Raspberry Pi OS

Download the Raspberry Pi OS image you chose and decompress the .xz archive with 7-Zip or a similar tool until you have a single .img file. Check the file size against the download page: a truncated download is a common cause of a card that writes successfully but never boots. Keep the decompressed .img file until the Pi has booted, so you can reflash without downloading again.

2. Insert the microSD card and note its letter

Put the microSD card in a reader, connect it, and note the drive letter in File Explorer. If Windows offers to format the card, choose Cancel. The flash will replace everything on the card, so formatting first is unnecessary and can mask a drive-letter error if you format the wrong drive.

3. Open Win32 Disk Imager as administrator

Run Win32 Disk Imager as administrator, click the folder icon, and select your decompressed .img file. Confirm that the Device drop-down shows the letter you noted in File Explorer. If the letter is missing, close and reopen the program, reseat the card, or try a different reader or USB port.

4. Write the image and eject safely

Click Write, confirm the dialog only after checking the drive letter again, and wait for the success message. Do not remove the card during the write. When it finishes, use Safely Remove Hardware, then remove the card from the reader. A rushed removal can leave the last writes unflushed, even when the progress bar looked complete.

5. Boot the Pi and wait for first boot

Insert the card into the Pi, connect a display, keyboard, and power last, and watch the first boot. Raspberry Pi OS expands its filesystem to fill the card on first boot and may reboot once. Give it several minutes before you conclude that something is wrong, especially on a slower card. The green activity LED should flicker during boot; a steady red LED with no green activity points to power or card problems, not to a normal slow boot.

6. Complete setup and make a backup

Follow the on-screen setup: set the country, password, and Wi-Fi if applicable, and update the system once you are on the desktop or command line. As soon as the Pi is working the way you want it, make a Read backup of the card with Win32 Disk Imager, as described in the backup guide. That backup is worth far more than the time it takes, because rebuilding a Pi from scratch always takes longer than restoring an image.

Hardware that makes this easier

If you are flashing cards regularly, a reliable card reader and a spare card save more time than any software trick. You can look at a Raspberry Pi kit (Sponsored) or a microSD card for Raspberry Pi (Sponsored) before you start, and keep the spare card for testing so a failed flash never leaves you without a working system.

Frequently asked questions

Do I need to format the microSD card before flashing Raspberry Pi OS?

No. Writing the image replaces the partition table and all partitions, so formatting first is unnecessary. If Windows offers to format, choose Cancel and write the image.

Why does my Pi take a long time on first boot?

Raspberry Pi OS expands its filesystem to fill the card on first boot and may reboot once during that process. Give it several minutes, and watch for green activity LED flicker, before assuming the flash failed.

Can I use Win32 Disk Imager instead of Raspberry Pi Imager?

Yes, if you already have a decompressed .img file. Raspberry Pi Imager adds downloading and first-boot customisation, while Win32 Disk Imager simply writes the raw image you give it.

For the full set of guides, see the Tutorials hub, and get the program from the download page. Related guides include: raspberry pi wont boot after flashing, expand filesystem after flashing, how to use win32 disk imager — each one covers one job in the same plain style as this guide.

This guide is for anyone who has a working card they cannot afford to lose: a Raspberry Pi project, a retro console setup, an industrial controller, or a camera card with a custom layout. It walks through the Read operation from start to finish, explains why the output file is so large, and shows how to store the backup so it is actually useful when the original card fails.

Expect one surprise if this is your first Read backup. The .img file will be as large as the whole card, even if the card looks nearly empty in File Explorer. That is not a bug. Read copies every sector, including empty space, and it does not compress anything.

Before you start

• Read does not erase the source card, but do not write to the card while a backup is running. Close programs that might modify it, and remove it from any device that could write logs or data during the copy.
• Make sure the destination drive on your computer has more free space than the full size of the card. A 64 GB card needs more than 64 GB free, plus room for the compressed copy if you plan to make one.
• Use a reliable card reader and do not disturb the card during the read. A loose connection can produce a backup that looks complete but contains read errors.
• Label the backup as soon as it finishes. A file named image.img tells you nothing in six months, while a name with the device, date, and purpose does.

Before you start, decide what you are backing up and why. If the card boots a device, a full Read image is the only backup that restores bootability without rebuilding the system. If you only need photos or documents from a FAT32 card, copying files may be simpler and far smaller. Choosing the right method saves disk space and avoids disappointment later, when you discover a file copy cannot boot a Pi.

Step by step

1. Insert the card and confirm its drive letter

Insert the card into your reader, wait for Windows to recognise it, and note the drive letter in File Explorer. If Windows offers to format the card, choose Cancel. You are reading the card, not repairing it, and formatting would destroy the very data you want to preserve. If the letter is missing, reseat the card or try another reader before continuing.

2. Open Win32 Disk Imager as administrator

Right-click Win32 Disk Imager and choose Run as administrator. Administrator rights are needed to read the raw device, and running without them is a common cause of access errors. The program is Windows-only, and there is no Mac or Linux version, so this guide assumes a Windows computer with a working card reader.

3. Choose an output file name and location

Click the folder icon next to the Image File field, browse to a folder with enough free space, and type a clear file name ending in .img, for example raspberry-pi-home-assistant-2026-10-24.img. Avoid saving the backup onto the same card you are reading from, which the program will not let you do sensibly, and avoid a nearly full drive that could run out of space halfway through.

4. Select the device and press Read

Choose the correct drive letter from the Device drop-down, then click Read. Read copies the whole device sector by sector, so the progress bar advances steadily and the output file grows to the full device size. Do not remove the card or let the computer sleep during the read, because an interrupted read produces a truncated image that may look plausible but will not restore cleanly.

5. Wait for completion and check the file size

Wait for the success message, then check the .img file in File Explorer. Its size should be close to the full capacity of the card, not to the amount of data you think is on it. If the file is much smaller, something went wrong, and you should repeat the read. Note the size and the MD5 or SHA-256 hash if you want a way to check the file later for corruption.

6. Compress and store the backup

Because a raw image includes empty space, it usually compresses very well. Use 7-Zip to compress it, as described in the compression guide, and keep at least two copies in different places. Test the backup only by restoring it to a spare card, never by restoring it over your only working original, because a restore overwrites its destination completely.

Where to keep the backup

A backup only helps if it survives the card it came from, so copy the finished .img file off the computer you flashed from. A dedicated backup drive (Sponsored) works well for large images, and you can also keep a second copy in cloud storage such as pCloud if you want an off-site copy. Label every file with the device, date, and contents before you upload it.

Frequently asked questions

Does Read erase or change the SD card?

No. Read only copies data from the card. It does not write to the card, format it, or change its contents. Still, avoid writing to the card during the backup so the copy is consistent.

Why is my .img file as large as the whole card?

Because Read copies the whole device sector by sector, including empty space, and it does not compress the output. A 32 GB card produces roughly a 32 GB file, which usually compresses well with 7-Zip.

Can I restore this backup to a different card?

Yes, if the new card is at least as large as the original. Cards sold as the same size can differ by a few megabytes, so a restore to a slightly smaller card can fail even when both are labelled 32 GB.

For the full set of guides, see the Tutorials hub, and get the program from the download page. Related guides include: restore img backup to sd card, compress img file 7zip, win32 disk imager allocated only read — each one covers one job in the same plain style as this guide.

This guide is for you if you have already downloaded an .img file and you need to get it onto a card or drive that will boot or run in another device. You do not need to understand disk geometry or command-line tools to follow it, but you do need to be careful about one thing above all else: the drive letter you select will be completely overwritten.

Win32 Disk Imager is Windows-only software released under the GPLv2 licence. The current version is v1.0.0, released on 2017-03-08. There is no Mac or Linux version of this program. The installer is about 12.6 MB and the portable zip is about 17.0 MB. The maintainer returned in November 2024, and no new release has appeared since, so you should not describe the project as permanently discontinued, but you should also not expect a new version soon.

Before you start

• Win32 Disk Imager Write overwrites the ENTIRE destination drive. Everything on that drive will be lost, including files in partitions you cannot see in File Explorer.
• Double-check the drive letter in File Explorer and in Win32 Disk Imager before every write. If two removable drives are plugged in, unplug the one you do not want to overwrite.
• Run Win32 Disk Imager as administrator, or Windows may block access to the drive. If you see an access error, closing other programs that use the drive and running as administrator usually fixes it.
• Use a card reader you trust and a card with enough capacity. The destination must be at least as large as the image, and a card that is a few megabytes smaller than the source card can fail even when both are sold as the same size.
• Download the .img file from a source you trust, and keep a copy of it until the flashed card has been tested in its target device.

It helps to prepare the destination before you open the program. Insert the card, wait for Windows to recognise it, and open File Explorer to confirm its letter and its size. If Windows offers to format the card, choose Cancel. You do not need to format first, because writing the image replaces the partition table and all existing partitions anyway. Formatting first only wastes time and can hide a drive-letter mistake.

Step by step

1. Download and install Win32 Disk Imager

Get the program from the download page, install it, and launch it as administrator by right-clicking its shortcut and choosing Run as administrator. The installer MD5 be92e76baabc97b3f093ff734dd3f75b and SHA-256 a51c9fc75c9caa44df03502838f229a70d484963f54675c241799093a59d8874 may be called verified, and you can compare them against your downloaded installer if you want an extra check before installing.

2. Select the image file

Click the folder icon next to the Image File field and browse to your .img file. If the file picker does not show your file, change the filter to show all files, and check the extension carefully. Win32 Disk Imager writes raw images, so the file should end in .img or, in some cases, .img.gz that you have already decompressed. Do not rename an ISO file to .img and expect it to work, because the contents are different even if the extension looks similar.

3. Select the correct device

Use the Device drop-down to choose the drive letter of your SD card or USB drive. Compare this letter with the one you saw in File Explorer, and check the size if anything looks uncertain. If the letter you expect is missing, close and reopen the program, reseat the card, or try another reader. Never guess at this step, because the next step erases the drive you selected.

4. Press Write and confirm

Click Write, read the confirmation dialog, and confirm only if the drive letter is the one you intend to erase. The progress bar shows the write advancing, and the speed depends on your card, your reader, and whether you are using USB 2 or USB 3. Do not remove the card, close the program, or put the computer to sleep while the write is running, because an interrupted write leaves a half-written card that will not boot.

5. Wait for the success message

Wait until Win32 Disk Imager reports that the write was successful, then use Safely Remove Hardware before taking the card out. If the program offers to verify, or if you want extra confidence, run a verify pass afterwards, which is covered in the Verify Only guide. Ejecting the card cleanly matters more than it seems, because Windows may still be flushing cached writes when the progress bar finishes.

6. Test the card in its target device

Put the card into the device it was made for, such as a Raspberry Pi, and power it on. A first boot can take longer than later boots, especially if the system expands its filesystem or generates keys on first start. If the device shows nothing at all, work through the boot checklist guide before you assume the image was bad, because power supplies, HDMI detection, and card seating cause many apparent failures.

Frequently asked questions

Does writing an image erase everything on the card?

Yes. Write overwrites the entire destination drive, including every partition and every file on it. Move anything you need off the card before you press Write, and double-check the drive letter.

Can Win32 Disk Imager make a bootable Windows USB from an ISO?

No. It does not parse ISO filesystems, so it cannot build a Windows installer USB from a Windows ISO. Use Rufus for that job, and reserve Win32 Disk Imager for raw .img files.

Do I need to format the card before writing?

No. Writing the image replaces the partition table and all partitions, so a prior format is unnecessary. If Windows asks to format the card, choose Cancel and write the image instead.

For the full set of guides, see the Tutorials hub, and get the program from the download page. Related guides include: how to back up sd card to img, flash raspberry pi os win32 disk imager, win32 disk imager verify only — each one covers one job in the same plain style as this guide.