फ़ाइल प्रकार पहचानकर्ता (मैजिक नंबर).

Text formats (CSV, Markdown, source code) look alike and are reported as plain text. Not an antivirus. Everything is calculated in your browser; nothing you type is uploaded.

Each format starts with characteristic bytes (“magic numbers”): %PDF for PDF, 89 50 4E 47 for PNG, PK plus word/ for DOCX, MZ for Windows programs. The extension is then compared with the content.

A file named invoice.pdf.exe starting with “MZ” is reported as a Windows program with a double-extension warning.