Raspberry Pi Imager Errors: Access Denied, Error Writing to Storage and Verify Failed

Short answer: Most Raspberry Pi Imager errors come from one of three things: Windows blocking Imager’s direct access to the card, another program holding the card open, or a faulty or fake SD card or card reader. For “access denied” or “error writing to storage” on Windows, check Windows Security’s Protection history and allow rpi-imager.exe through Controlled folder access, then close File Explorer windows showing the card. For “verifying write failed,” try a different card reader, then test the card. Don’t skip verification to get past the error. The current Imager is 2.0.11.1, from raspberrypi.com.

Raspberry Pi Imager errors and what they usually mean

The fixes below come from Raspberry Pi’s documentation, from Raspberry Pi Imager maintainers on the project’s GitHub issue tracker, and from Microsoft’s Windows Security documentation. We link each one in the sources.

Fix “access denied” and “error writing to storage” on Windows

1. Allow Imager through Controlled folder access

Controlled folder access is a Windows Security feature that, in Microsoft’s words, blocks “unauthorized or unsafe apps from accessing or changing files in protected folders.” It can also stop an imaging tool from writing to a card.

In a 2023 reply on the Imager issue tracker, maintainer maxnet agreed that Windows Defender may block Imager from accessing SD cards this way, and noted that Windows’ own warning “is only there for a second” before it disappears into notifications. In September 2026, maintainer tdewey-rpi pointed another user to the same cause, noting that Controlled folder access is off by default unless you turn it on yourself or your organization’s device management turns it on.

To check and fix it:

1. Open Windows Security and go to Virus & threat protection.
2. Open Protection history. If you see a blocked action involving rpi-imager.exe, that’s your cause.
3. Go to Manage ransomware protection, then Allow an app through Controlled folder access.
4. Add rpi-imager.exe from its install folder, then run the write again.

Don’t turn Controlled folder access off entirely just to write a card. Allowing one app is enough. If a work or school laptop manages these settings, you may not be able to change them. Use another computer.

Maintainer lurch has also suggested that other security settings on a PC can block the low-level access imaging tools need. If you use third-party antivirus, check its blocked-activity log for Imager.

2. Close anything that has the card open

In a September 2026 issue about “access denied” and write-protected errors, maintainer tdewey-rpi said Imager deletes the card’s existing partition layout before writing. The working theory for that failure was that File Explorer “or another application” was viewing the drive and holding locked handles on it when the write began.

So before you select Write:

• Close every File Explorer window showing the card.
• Close photo importers, backup tools or disk utilities that react to new drives.
• Remove other USB drives, so you can’t pick the wrong device.

3. If you write custom images on Windows 11

An open issue on the Imager tracker reports “Error writing to storage device” failures with custom .img and .img.xz files, starting with version 2.0.2. Maintainer tdewey-rpi wrote that Imager 2.0 “uses a different Windows API to write files,” that some users linked the problem to the Windows 11 25H2 update, and that Imager 2.0.7 added “further mitigation and debugging.” As of September 26, 2026, the issue is still open. Several users in that thread fixed their failures by allowing Imager through Controlled folder access, so try step 1 first.

Fix “verifying write failed”

After writing, Imager reads the card back to confirm it matches the image. Raspberry Pi’s documentation recommends that you let this step finish. A failed verification means what was read back differs from what was written.

The Imager maintainers give consistent advice for this error:

1. Try a different card reader. Maintainers have repeatedly suggested this first. Maintainer lurch notes that one common trap is using a new SDXC card in an old reader that only supports SDHC.
2. Try a different USB port. Some users report that ports on the back of a desktop are more reliable than front-panel ports.
3. Try a different card. Maintainer maxnet pointed out that a card that boots isn’t proof it’s fully working, because Imager reads back the whole card.
4. Test the card. Maintainers have suggested H2testw on Windows, or the tools in the Fight Flash Fraud documentation, to check whether a card really has its advertised capacity. Fake cards that report more space than they have are a known cause.

Don’t skip verification to “fix” it. Maintainer lurch warned that while skipping verification may appear to work, “you may run into OS corruption problems later.” The same applies to tools that don’t verify at all. The same maintainer noted that Win32 Disk Imager “doesn’t do verification after writing,” so it can seem to succeed and leave you with a partly corrupted card.

If Imager and another tool such as balenaEtcher both fail on the same card and reader, a maintainer’s view is that the card or the reader is probably faulty, and that other tools would likely fail too. Our balenaEtcher, Rufus and Ventoy comparison explains which tools verify their writes.

Fix slow writes

Raspberry Pi’s documentation says faster storage devices with higher read and write speeds improve performance. If you’re not sure which card to buy, it suggests an official Raspberry Pi microSD card.

A very slow write can also be a warning sign. On an April 2026 report, maintainer tdewey-rpi read the user’s log and explained that Imager had seen a single write take over 10 seconds and had reduced how many writes it queued to the device. The maintainer said the log suggested “major issues with your storage device.” Another maintainer suggested trying a USB card reader instead of the computer’s built-in slot.

So for slow writes:

• Try a USB card reader instead of a built-in slot, or a different reader.
• Try another card. Slow writing on one card but not another points to the card.
• If writes are very slow and verification also fails, test the card before trusting it.

Pick the right card

From Raspberry Pi’s “Recommended minimum storage requirements”:

The documentation also says you can use any SD card under 2 TB. Larger cards aren’t supported because they exceed the limits of the MBR partitioning the card uses. Other operating systems have their own requirements. For Home Assistant, see our Home Assistant install methods guide.

Buy cards from a retailer you trust. Maintainers have noted that fake SD cards are common, and that a fake card can cause verification failures.

Other routes when your computer won’t cooperate

• Network Install. Raspberry Pi documents a way to run Imager on the Pi itself over the network, with no separate computer or card reader. It needs a Raspberry Pi 4B or later flagship model, or a Raspberry Pi 400, 500 or 500+, plus a monitor, keyboard and wired internet connection. tdewey-rpi suggested it on a report where a PC kept failing.
• Imager on a working Pi. Once one card works, you can install Imager inside Raspberry Pi OS and write more cards with a USB reader attached to the Pi.
• Collect a log. If you want to report a bug, tdewey-rpi describes two ways to get Imager logs on Windows: start Imager with --log-file, or watch it live with Microsoft’s DebugView run as Administrator. In Imager 2, Ctrl+Shift+P after a write saves a performance log.

What not to do

• Don’t download Imager from a mirror site. Get it from raspberrypi.com or the official GitHub releases. Our Raspberry Pi Imager app page links both and lists the version. Also see how to spot fake download sites.
• Don’t disable your antivirus entirely. Allow Imager instead.
• Don’t skip verification on a card you plan to rely on.
• Don’t assume the card is dead. Maintainer tdewey-rpi suggested that cards that seem “broken” after a failed write may just have a bad partition table. Windows Disk Management, or GParted on Linux, can clear it.

Questions

Why does Raspberry Pi Imager say “access denied”?

Usually Windows Security’s Controlled folder access, antivirus, or another program holding the card open. Allow rpi-imager.exe and close Explorer windows on the card.

How do I allow Raspberry Pi Imager through Controlled folder access?

Windows Security > Virus & threat protection > Manage ransomware protection > Allow an app through Controlled folder access, then add rpi-imager.exe.

What does “verifying write failed” mean?

The data Imager read back didn’t match the image. The usual causes are a faulty card, a faulty reader or a fake card.

Can I skip verification in Raspberry Pi Imager?

Yes, there’s a Skip verification button, but a maintainer warns it can leave you with OS corruption later. Raspberry Pi recommends completing it.

Why is Raspberry Pi Imager so slow?

Write speed depends on the card and reader. Very slow writes can mean the card is failing.

What size SD card do I need?

Raspberry Pi recommends at least 32 GB for Raspberry Pi OS with a desktop and 8 GB for Lite. Cards must be under 2 TB.

Is my SD card broken after a failed write?

Not necessarily. It may only have a damaged partition table. Test it with H2testw before throwing it away.

Can I use balenaEtcher instead?

Yes. Home Assistant’s docs suggest it when Imager isn’t supported on your platform. If both tools fail the same way, suspect the card or reader.

What is the latest Raspberry Pi Imager version?

2.0.11.1, released August 17, 2026, according to the official GitHub releases.

Sources

• Getting started with your Raspberry Pi (Install an OS, boot media), Raspberry Pi documentation
• install.adoc (documentation source), Raspberry Pi on GitHub
• Raspberry Pi Imager releases (2.0.11.1), GitHub
• Error writing to storage (issue 525), rpi-imager GitHub
• Imager complains access denied and/or write protected media (issue 1739), rpi-imager GitHub, September 2026
• “Error writing to storage device” failures starting with 2.0.2 (issue 1489), rpi-imager GitHub
• Verifying write failed (issue 41), rpi-imager GitHub
• Verifying write failed (issue 856), rpi-imager GitHub
• Verification fails constantly (issue 1598), rpi-imager GitHub
• Error writing file to disk (issue 743), rpi-imager GitHub
• Virus and threat protection in the Windows Security app (Controlled folder access), Microsoft Support
• Fight Flash Fraud (f3) documentation
• Install Home Assistant on Raspberry Pi, Home Assistant