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uk Technology & digital loss

What to do if…
an important file is corrupted and will not open

Produced and maintained by PanicStation.org Published: Last reviewed: Editorial policy UK guide

Short answer

Do not overwrite or delete the original file. Make a separate copy, then check version history and backups before using any official repair feature on the copy.

Do not do these things

  • Do not save a blank, incomplete or garbled version over the original file.
  • Do not test repair software on your only copy.
  • Do not change the filename extension merely to make the file open.
  • Do not repeatedly open, move or alter the original after making a safe copy.
  • Do not upload confidential, personal or work files to an unknown online repair service.
  • Do not erase or reformat the storage device while the only copy remains at risk.
  • Do not connect backup drives if several files changed unexpectedly or a ransom note appeared.
  • Do not pay or reply to a ransom demand before obtaining specialist support.

What to do now

  1. Stop editing the file. If an application has opened it incorrectly, close it without saving over the original.
  2. Locate the original file and make a copy with a different name in a different folder or on another healthy storage device. Keep the original untouched and use the copy for every test.
  3. Record the exact error message. Take a screenshot and note the file name, extension, size and where it was stored.
  4. Check whether another known-good file of the same type opens normally. Then try opening the copied file through the trusted application’s File and Open menu or with another trusted application that supports that file type.
  5. Check for an earlier version before attempting repair. Look in OneDrive, Google Drive, Dropbox, Windows File History, Time Machine or your organisation’s backup system. Restore or download the earlier version under a new name where the service allows this.
  6. Use only the software provider’s documented recovery option on the copy. Supported Microsoft Word, Excel and PowerPoint versions may provide Open and Repair from the Open dialogue.
  7. If it is a work, school or shared file, contact the organisation’s IT team or the file owner before installing recovery software or sending the file elsewhere. They may have server backups or version history that you cannot access.
  8. If several files suddenly became unreadable, extensions changed, a ransom note appeared or security software reported malware, disconnect the affected device from wired, wireless and mobile network connections. Leave removable backups disconnected and contact IT or follow National Cyber Security Centre guidance from a different device.
  9. If the storage device repeatedly disconnects, cannot copy the file or appears physically damaged, stop retrying. Preserve the device and ask a reputable data-recovery specialist whether it can be assessed without altering the original data.

What can wait

You do not need to determine the cause, buy recovery software, replace the device, rebuild the file from memory or redesign your backup system now. Protecting the original and checking existing versions can come first.

Important reassurance

A file that will not open is not necessarily completely lost. An earlier version, automatic recovery copy or backup may still be available, and the problem may affect only one copy or one application.

Scope note

This guide covers immediate steps to protect the original file and check common recovery routes. Complex corruption, failing storage hardware, encryption or malware may require qualified technical or cyber-security support.

Important note

This is general information, not professional data-recovery or cyber-security advice, and recovery cannot be guaranteed. Check how any repair provider will handle, store and protect sensitive files before sharing them.

Additional Resources

Closely connected guides that may be useful during the same situation or its immediate aftermath.

About this guide

This guide was produced and is maintained by PanicStation.org using its published editorial process. Official and specialist sources are checked where relevant, and AI-assisted tools may be used for drafting, organisation, and consistency checks. The site operator remains responsible for publication, revision, and removal decisions.

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