File Extension Fixer
Find the extension a file actually deserves, based on its bytes — not its name.
File Extension Fixer
Many “file won’t open” problems are just a wrong suffix. This reads the real format from the file’s signature and tells you the extension it should have.
Details
File details appear here.
When to use this
Use it whenever an app rejects a file that “should” open. Typical cases: a photo downloaded with a .bin extension, a document someone emailed without an extension, a file whose type was guessed wrong by an old browser, or a backup that came back with a generic .dat suffix. The tool reads the first bytes — the format’s “signature” — which almost never lies.
Worked example
You have photo.dat that won’t preview. Drop it in: the header is 89 50 4E 47, the PNG signature, so the tool recommends renaming to photo.png. Download the copy with the new name and every viewer opens it. No re-encoding, no quality loss — the pixels were always PNG.
What it can and can’t do
It identifies the container format (PNG, JPEG, PDF, ZIP, etc.) and suggests the matching extension. It does not convert the file — a PNG renamed to .jpg is still a PNG, just labeled correctly. For true format conversion (changing the bytes), use the Image Converter. Plain-text formats have no signature, so those will report “no recognizable signature” and need a manual call.
FAQ
Will renaming change my file? No. The download is an exact byte copy with a different name. The original on your disk is untouched.
It says “no recognizable signature.” Is the file broken? Not necessarily. Text, CSV, and many config files have no magic bytes. If the app that created it expects that format, it is fine.
Can I fix a whole folder at once? Browsers can’t bulk-rename local files for privacy reasons. This tool fixes one file at a time; the Batch Rename Fixer handles lists of names with a script you run yourself.