How to use the File Type Detector
The File Type Detector reads the start of one selected file, checks its bytes against known signatures, and compares the result with the filename extension. It reports the format, standard extension, MIME type, category, confidence, and a hex and ASCII view of the header. The file itself stays unchanged.
- Drop any file here, or click
browse fileto choose one file. - Review Detected format, Standard extension, MIME type, Category, and Confidence.
- Compare Claimed extension with the detected format and read the match message.
- Inspect Match basis and Header preview (hex & ASCII, offset in hex) to see the bytes behind the result.
Identify a file type from its signature
The extension comes from the filename. The detector checks the opening bytes against its signature database and assigns a confidence level. A binary signature match receives high confidence when the bytes match exactly. A ZIP file can receive medium confidence when its outer signature is present but the header does not identify the container.
Input: photo.jpg
Output: JPEG, standard extension .jpg, extension matchesHow ZIP-based file detection works
DOCX, XLSX, PPTX, EPUB, JAR, APK, and plain ZIP files can start with the same ZIP signature. For a ZIP local-file header, the detector checks the first internal entry and, when present, a mimetype marker. Match basis names the evidence or says that the header cannot identify the container more closely.
What happens when no binary signature matches
After the binary checks, the detector decodes part of the header as UTF-8. It looks for XML, HTML, JSON, CSV, or plausible plain text. XML, HTML, JSON, and CSV receive medium confidence because their result comes from text structure. Plain text receives low confidence. The result is Unknown / unrecognized when neither a binary signature nor plausible text matches.
What the header preview can tell you
Header preview (hex & ASCII, offset in hex) shows up to the first 64 bytes, their hexadecimal offsets, byte values, and ASCII characters. That preview is part of the header read by the detector. It cannot establish that a file is valid, safe, corrupt, or complete.
Examples of file type mismatches
- If
report.pdfproduces a different detected format, the result shows that its name and content disagree. - A file with no extension can still receive a format result when its header matches a known signature. The tool then has no claimed extension to compare.
- An unfamiliar file can produce an unknown result. The header preview shows the bytes that were read.
Choose a different file analysis tool
Use File Management Analyze Tools for another file or folder inspection task. Choose Duplicate File Finder to compare multiple files by size and SHA-256 hash. Choose File Encoding & Line-Ending Analyzer for text encoding, line-ending, count, or preview details. Choose File Age & Path-Length Analyzer for item age or path length.
The script reads up to 4,160 bytes from the selected file in the browser and sends no file content to a server. It does not scan for malware, parse EXIF, XMP, or document metadata, repair or convert files, extract archives, or modify contents. Proprietary, encrypted, corrupted, or uncommon content can remain unknown when it does not match the signature database or a text heuristic.
Frequently asked questions
How can I identify a file type when the extension is wrong?
The File Type Detector reads the file header, compares it with known signatures or textual patterns, and reports when the detected format disagrees with the claimed extension.
Is the file uploaded during type detection?
No. The browser reads up to 4,160 bytes from the selected file. This detection workflow sends no file content to a server.
Can the file type detector read EXIF or document metadata?
No. It identifies the format from header bytes or textual patterns. It does not parse EXIF, XMP, document properties, or other embedded metadata.
Why does file type detection return unknown?
Unknown means that no documented binary signature or plausible text pattern matched the header bytes. Proprietary, encrypted, corrupted, and uncommon formats can produce this result.
Does identifying a file type check if it is safe?
No. A recognized or unknown format result is not a malware scan. It does not establish that the file is safe, unsafe, valid, or corrupt.