File signature type hints
Check common signatures, filename relations and explicit unknown results from bounded local file samples; download the complete evidence JSON.
- 1Add input
- 2Review and run
- 3Get your result
Tool input and files are processed in this browser without being uploaded.
Before you start
Check common signatures, filename relations and explicit unknown results from bounded local file samples; download the complete evidence JSON.
How to use this tool
- Select the original local files, including missing or incorrect extensions.
- Build the report and review unknown, incomplete, multiple-hint and extension-relation outcomes per file.
- Use the exact read ranges to identify unexamined regions; a signature is not a validity check.
- Copy the complete JSON or download file-signature-hints.json. Retain the originals and retry after cancellation.
Supported inputs and limits
Select 1–100 original local files of any extension. Each filename is limited to 512 UTF-16 units; the original file size must be a nonnegative safe integer. Pasted text is not a file source.
The report gives hints for PNG, JPEG, GIF, WebP, PDF, ZIP, GZIP, WAV, Ogg, FLAC, MP4-brand ISO BMFF, ELF and PE. These are one identification task; other types can remain unknown or appear only as an extra library diagnostic.
For each file, read at most the first 8,192 bytes and the last 65,536 bytes without overlap. The original size and exact read ranges remain in the report. Any middle gap is unexamined; large originals are not fully loaded or hashed.
Unknown, empty, incomplete, extension mismatch and multiple visible signatures are explicit outcomes. A matched signature, library clue or declared-size check does not prove the whole file is valid, safe or openable. Not all polyglots are detectable.
ZIP and GZIP hints do not decompress contents, identify Office subtypes or inventory entries. Audio, images and executable bodies are not fully parsed, decoded or executed. Files are not renamed or repaired.
All rows and evidence are delivered in file-signature-hints.json (application/json), up to 1 MiB. The screen previews the first 4,000 Unicode code points; copy and download preserve the complete compact UTF-8 JSON.
The maximum sampled read for 100 files is 7,372,800 bytes, below the 8 MiB guard. The fixed-schema complete JSON bound is 521,804 bytes, below 1 MiB; neither guard is an independent reachable capacity edge.
A 60-second deadline covers preparation, reads, Worker loading and processing. Cancel or timeout settles immediately, stops further sampling and terminates any Worker. No partial report is delivered; the original selected files remain available for retry. File contents and names are not uploaded.
Worked example
Example input
Select an original beginning with PNG signature bytes; text is not an input source.
Example options
{}Example output
{"profile":"bounded-signature-13-v2","libraryVersion":"[email protected]","plannedRead":77,"rows":[{"name":"temporary-io-recovery","size":77,"state":"recognized-signature-hint","candidates":["png"],"evidence":[{"type":"png","offset":0,"hex":"89504e470d0a1a0a","aliases":["png"],"mime":"image/png","state":"signature-hint"}],"incomplete":[],"library":{"ext":"png","mime":"image/png"},"libraryError":null,"extension":null,"extensionRelation":"absent","readRanges":[{"start":0,"end":77},{"start":77,"end":77}],"bytesRead":77,"limitations":["signature-hints-only","file-validity-and-safety-unknown","unread-regions-unexamined","all-polyglots-not-detectable"]}]}When something does not work
Reduce the selection or adjust a copy’s name if limits are exceeded; reselect originals after a read error. Retry the same files after cancellation or timeout. Unknown is an honest bounded-sample result; do not guess an extension or execute the file.
Frequently asked questions
Does a matched signature mean the file is valid?
No. recognized-signature-hint only means the bounded signature agrees with the library clue. The body, unread regions and safety remain unknown.
Does this recover directories or rename files?
No. This completes the selected files’ type-hint check. Directory recovery, actual renaming and complete format validation are separate steps.
Documentation & further reading
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