How to use the File Information Viewer
- Choose any file.
- See what it really is, based on its contents rather than its name.
- Optionally calculate a SHA-256 checksum to verify it.
Why the extension isn't enough
A file's extension is just part of its name and can be changed by anyone. Most formats start with a recognisable “magic number”: PDFs begin with %PDF-, PNGs with the bytes 89 50 4E 47, ZIP-based formats like DOCX and XLSX with PK. This tool reads those bytes — and for Office files, the structure inside the ZIP — to identify the real type.
When this is useful
- A file won't open and you want to know why.
- A download has a strange or missing extension.
- An email attachment claims to be a PDF but you're suspicious.
- You need a checksum to confirm a download — or use the hash generator for MD5 and SHA-512 too.
Frequently asked questions
Is my file uploaded?
No. Only the first few kilobytes are read in your browser (the whole file if you ask for a checksum).
Can it detect viruses?
No. It identifies file types; it isn't an antivirus scanner.