What Am I Using?
File won’t open?
Compare a known-good file, check the extension and find out whether the problem is the file, an incomplete transfer or the app used to open it.
Can the same app open another file of that type?
Use a small known-good file and check that the extension matches, such as PDF or JPG.
Device and operating system
Check whether the original is complete
A download, cloud sync or transfer can leave a partial file.
- Keep the original and compare its size with the sender’s copy if available.
- Download a fresh copy from the trusted source or ask the sender to export again. Avoid repair uploads for confidential files.
Choose an app that supports the format
An incorrect default app can fail even when files are intact.
- Check the file’s extension in its information view. Open it from a trusted app that supports that format.
- If that succeeds, change the default through the normal system prompt if you want. Keep warnings for unexpected executable files in place.
Ask the sender to verify the format
A file extension describes an expected format but can be wrong or missing.
- Record the full extension, size and error. Ask the sender what app created it and request a standard export.
- Keep the source copy and avoid renaming the extension as a conversion.