File Type Identifier
Choose files to see what each one really is, judged by its first bytes rather than its name, and whether its extension is right.
Drop files here, or
Up to 100 files, 25 MB each. Only the first 64 KB of each is read: nothing is opened, run or uploaded.
It reads only each file’s first bytes and compares them with known signatures. It never opens, runs or uploads a file.
What a file is, whatever its name says
A file that won’t open, a photo a website refuses, an attachment called invoice.pdf that isn’t a PDF: often the name and the contents disagree. Many formats begin with fixed bytes set by their specification, a signature of their own. This page reads those bytes and tells you what the file really is.
How to use it
- Choose up to 100 files, or drop them on the box.
- Read each result: what the first bytes say, and the extension that fits.
- Where the name disagrees, rename the file with the right extension, then open it again.
What it recognizes
- Pictures: JPEG, PNG, GIF, WebP, AVIF, HEIC, BMP, TIFF, ICO and PSD.
- Documents and archives: PDF, ZIP, and the formats built on ZIP (DOCX, XLSX, PPTX, ODT, EPUB), GZIP, 7z, RAR, TAR and older Office files.
- Sound and video: MP3, AAC, MP4, MOV, M4A, WebM, MKV, WAV, AVI, Ogg, FLAC and MIDI.
- Programs, fonts and more: Linux and macOS programs, Windows EXE and DLL files, SQLite databases, WOFF, TTF and OTF fonts, and text, with its byte-order mark if it has one.
Reading the result
A warning means the name’s extension belongs to a different format. Renaming only changes the label: it doesn’t convert anything, so give the file the extension of what it already is. If you need another format, use a converter such as PNG to JPG. A program dressed up with a document’s name gets a word of caution: a program disguised as a document is an old trick for getting people to run it.
Good to know
- Text has no signature, so a CSV, a JSON file and a note all read as text; only a text file named like a picture or PDF is questioned.
- A DOCX is a ZIP inside, and so are XLSX, PPTX, ODT and EPUB files: the page tells them apart by the names of their first entries.
- Camera raw files such as DNG are built on TIFF, so they show as TIFF.
- Only the first 64 KB is read, so even a large video is identified at once.
- Your browser’s guess comes from the name alone, which is why it can be wrong.
- Need to know it’s the exact file published? The Hash Generator compares it with the site’s checksum.