How to magic bytes vs file extension: which detection method wins?
- Step 1Drop the file you want to test — Upload any file — the tool reads both its extension and inspects the binary header simultaneously.
- Step 2View the comparison result — The report shows the declared extension, the detected MIME type from magic bytes, and whether they agree or conflict.
- Step 3Interpret the mismatch — A conflict means the extension has been changed or the file has been corrupted — treat it as untrusted until verified by additional means.
Frequently asked questions
Can magic bytes also be faked?+
Yes, but it requires deliberate binary editing. Extension renaming takes seconds; forging correct magic bytes in a working malicious file requires deep format knowledge. Dual-layer validation catches both.
What formats have the most reliable magic bytes?+
ZIP, PDF, PNG, JPEG, GIF, ELF, and PE (Windows executables) all have mandatory, stable magic bytes at offset 0. Office OOXML formats (.docx, .xlsx) are ZIP archives and start with PK\x03\x04.
Why do CDNs still trust extensions?+
Performance — reading file bytes requires storage access before serving headers. Most CDNs validate on upload and trust the stored metadata at serve time. Validate before upload to break this assumption.
Privacy first
Every JAD Security operation runs entirely in your browser. Files, passwords, and PGP private keys never leave your device — verified by zero outbound network requests during processing.