File Type Checker

What is File Type Checker?

File Type Checker reads the first bytes of a file, its signature, to identify the real format regardless of its name. It flags extensions that do not match the content, including programs disguised as documents or photos. Only the first 4 KB are read, on your device.

File extensions can be wrong or deliberately misleading, for example an attachment named invoice.pdf that is really a program. Checking the signature reveals the true format, helps you open files with the right app, and warns you before you run something unexpected.

How to use File Type Checker

1. Choose any file.
2. Press Check file type.
3. Read the detected format, MIME type and whether the extension matches.

Key features

• Recognises 50+ formats: documents, images, audio, video, archives, fonts, executables
• Extension mismatch warning
• Warns about disguised executables
• Shows the first bytes in hex
• Works with files of any size

Why use this file type checker

• Spot disguised or mislabelled files
• Identify files without an extension
• See the MIME type and first bytes
• Reads only the first 4 KB, locally

How it works

The first bytes of the file are compared with known format signatures; the extension is then checked against the result.

File Type Checker examples

Important notes before you rely on the result

• Files are read on your device and never uploaded.
• A matching signature or checksum confirms a file’s format or integrity, not that it is safe. Scan unknown programs with antivirus software.

Limits and supported formats

• Signatures identify the format, not whether a file is safe or valid; damaged files can still match.
• Plain-text formats (CSV, code, Markdown) share no signature and are reported as plain text.

Privacy and data handling

Processed on your device. Your files are never uploaded to a server.

File Type Checker: frequently asked questions