What Can I Do With This File? Convert
Drop any file to identify what it really is, then jump straight to a tool that can work on it — with the file already loaded.
What Can I Do With This File? is a free online tool that drop any file to identify what it really is, then jump straight to a tool that can work on it — with the file already loaded. It runs entirely in your web browser using plain JavaScript, so files are processed on your own device and never uploaded to a server. There is no sign-up, no file size limit imposed by the site, no watermark and no paid tier.
- Price
- Free — no account, no quota, no watermark
- Category
- Convert
- Where it runs
- In your browser, on your device
- Files uploaded
- None
- Technology
- plain JavaScript
- Settings
- None — it just works
- Works offline
- Yes, after the first visit
About What Can I Do With This File?
A file name is a claim, not a fact. Renaming a PNG to `.jpg` fools every program that trusts the extension, and the MIME type your browser reports is guessed from that same extension — so it is the same claim made twice, not corroboration. This reads the first 64 bytes instead. Nearly every binary format begins with a signature: `%PDF` for PDFs, the bytes `89 50 4E 47` for PNG, `FF D8 FF` for JPEG, `PK` for anything ZIP-based, which includes every DOCX, XLSX, PPTX and EPUB. Where the signature and the extension disagree, the signature is right, and the file is usually fine — just misnamed, which is exactly why one particular program refuses to open it.
How to use it
- Everything what can i do with this file? needs is on this page.
- Your input is processed locally and discarded when you close the tab.
Under the hood
| Runs on | plain JavaScript — runs the whole thing |
Questions
Why does my file say "No signature"?
Because text-based formats do not have one. Plain text, CSV, JSON, HTML, SVG, Markdown and source code all begin with ordinary characters, so there is nothing to detect — for those, the extension genuinely is the only clue. That result is normal and not a problem with the file.
My .docx shows as a ZIP archive. Is it corrupt?
No — a DOCX genuinely is a ZIP archive containing XML, and so are XLSX, PPTX, ODT, EPUB and JAR. They all share the same `PK` signature, and telling them apart means reading the archive index. Rename one to .zip and you can open it and look inside.
How much of my file is read?
The first 64 bytes and nothing else. That is all any signature needs, and reading further into a 400MB video would be pointless. Nothing is uploaded at any stage — the check happens in your browser, and so does whatever tool you pick next.
Does the file really carry over to the next tool?
Yes. Choosing a tool stores the file in your browser's own IndexedDB, navigates, and hands it straight to that tool, which then deletes the stored copy. It is single-use, expires after five minutes, and never crosses the network — the file has no reason to leave your device just to move between two pages of the same site.