Quick answer: This file type checker identifies a file from its signature (the first bytes of its content) rather than its name: images, videos, audio, documents, Office files, archives, fonts and programs, more than 80 formats. It flags wrong or missing extensions and programs disguised as documents, and can return copies with the correct extension. Only the start of each file is read, on your device.
A file with no extension, a “.pdf” that won't open, or an attachment that looks suspicious: check what it really is from the first bytes of its contents, and get a copy with the right extension.
File type checker at a glance
| Price | Free, no sign-up, no watermark, no daily limit |
|---|---|
| Accepts | Any file |
| Largest file | 100 GB per file, several files at once |
| Where it runs | In your browser: files are never uploaded |
| Works on | Any modern browser on iPhone, Android, Windows, Mac and Linux |
| Send the result | Download it, or send it free with a link or by email (up to 20 GB) |
How to use the file type checker
- Choose or drop the files you want to check.
- Tick “copies with the right extension” if you want fixed files back.
- Press Check file types.
- Read the result for each file, or download the report.
Why the extension can be wrong
An extension is just part of the name, and anyone or any app can change it. Downloads sometimes lose it, phones save HEIC photos as “.jpg”, and messaging apps rename files. The content, however, starts with a signature (the “magic number”) that says what the file is: %PDF for a PDF, PK for ZIP-based formats such as Word and Excel, ftyp boxes for MP4, MOV, HEIC and AVIF. This tool reads that signature.
What it recognises
- Images: JPEG, PNG, GIF, WebP, HEIC, AVIF, TIFF and camera RAW, BMP, ICO, PSD, SVG, with the size in pixels.
- Video and audio: MP4, MOV, MKV, WebM, AVI, MPEG-TS, 3GP, WMV, MP3, M4A, WAV, FLAC, Ogg, AIFF.
- Documents: PDF (with its version, and whether it is password-protected), Word, Excel and PowerPoint (old and new), OpenDocument, EPUB, RTF, HTML, XML, JSON, CSV, subtitles.
- Archives and programs: ZIP, RAR, 7z, GZIP, TAR, ISO, APK, JAR, Windows EXE, macOS and Linux programs.
Spot disguised programs
A common trick in scam emails is a program named like a document, such as “invoice.pdf.exe” or an EXE renamed to “.pdf”. If a file is really a program, the checker says so clearly. Don't open it unless you trust the sender. For files you received with a published checksum, also verify them with the file hash checker.
Instant and private
Only the first 64 KB of each file is read (plus the index at the end of ZIP files), so even a 50 GB video is checked instantly. The files never leave your device.
How this compares
| This tool | Online converters (e.g. ezyZip or CloudConvert) | Desktop apps (e.g. 7-Zip or WinRAR) | |
|---|---|---|---|
| Your file is uploaded | No | Yes, to their servers | No |
| Install or account | None | Account for some features | Install needed |
| Watermark or daily limits | None | Common on free plans | Depends on the app |
Plans of other services change; check their sites. More file tools.
Frequently asked questions
How do I find out what type a file is?
Add it and press Check file types. The result shows the real format, its MIME type and whether the extension matches.
My file has no extension. What do I do?
Check it here, tick “copies with the right extension”, and download the copy: it opens in the right app.
Can it tell a DOCX from a ZIP?
Yes. It looks inside ZIP-based files and recognises Word, Excel, PowerPoint, EPUB, APK and JAR.
Is it safe to check a suspicious file?
Yes. The file is only read, never opened or run, and it stays on your device.
Are my files uploaded?
No. Only the start of each file is read, in your browser.
Need to send a big file?
Send files up to 20 GB with a download link or by email. Free, no account needed, original quality.
Send large files free