File Type Detector
Compare file magic bytes, filename extension, browser MIME, and text-content hints locally
Signature detection reads at most the first 10 MB. The file is never uploaded, executed, or opened as active content.
The file signature, extension, and MIME comparison will appear here.
About this tool
File Type Detector reads up to the first 10 MB of a local file and compares four independent signals: recognized binary magic bytes, the filename extension, the browser-provided MIME type, and a conservative text-content hint for JSON, XML, SVG, HTML, CSV-like, or plain UTF-8 data. The file-type signature engine recognizes common images, documents, archives, audio, video, executables, fonts, and container formats. Mismatches are reported rather than silently trusting the name. Signature detection identifies a format family, not whether content is safe, uncorrupted, standards-compliant, or malware-free; the file is never executed or uploaded.
Scenario Recipes
Triage a file with a suspicious extension
Goal: Compare independent format signals before opening unknown content
- Drop the file without renaming it and record magic type, extension, and browser MIME.
- Treat any mismatch as an investigation signal and keep the file isolated.
- Use approved malware scanning and format-specific validation before opening or processing it in a trusted workflow.
Result: A local format comparison report that does not confuse identification with a safety verdict.
Frequently Asked Questions
What are magic bytes?
They are format-specific byte patterns near the start of many binary files and are usually stronger evidence than a filename extension.
Why can browser MIME disagree with the signature?
Browsers and operating systems often infer MIME from the filename or upload metadata rather than inspecting file content.
Can the tool identify text files?
When no binary signature matches, it provides conservative hints for JSON, XML, SVG, HTML, CSV-like, and plain UTF-8 text.
Does a matching signature prove the file is safe?
No. It does not scan malware, validate full file structure, verify checksums, or safely render active content.
How much of a file is read?
Files may be up to 100 MB, while signature inspection reads at most the first 10 MB to limit memory use.
Is the file uploaded?
No. Byte reading, signature matching, MIME comparison, and report generation happen locally.
Keep browsing