File signature inspector

Check what a file starts with.

Compare a file name and browser-reported MIME type with recognizable binary signature bytes. Only the first 64 bytes are read, and nothing is uploaded.

Choose or drop any fileOnly its first 64 bytes are inspected locally.

Extensions, MIME types, and magic bytes

A filename extension is a label. The MIME type exposed by a browser is commonly inferred from that label. Signature bytes—sometimes called magic bytes—provide another signal based on file contents, but complete validation requires a parser designed for that format.