File Type Detector
Identify a file by its magic bytes.
Runs entirely in your browser — nothing you enter is uploaded, logged, or tracked.
A file’s extension can lie, but its first few bytes — the “magic number” — usually reveal its real format. Drop in any file to identify its true type from a library of signatures (images, documents, archives, audio, video, executables) and compare it to the extension. Everything is read locally; nothing is uploaded.
Frequently asked questions
How does it work?
It reads the first bytes of the file and matches them against known file signatures (PNG starts with 89 50 4E 47, PDF with %PDF, ZIP with PK). The extension is only a hint; the bytes are the truth.
Why does the detected type differ from the extension?
Either the file was renamed, or it’s a container format (DOCX/XLSX/JAR are ZIP files). A mismatch can also be a sign of a disguised or malicious file.
Is my file uploaded?
No — only the first bytes are read, entirely in your browser.