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Detect the true file type (MIME type) and view file name and size details. Perfect for both developers and everyday users.
Choose filesClick or drag file here
Supports detection of real formats for various file types
Max 100 MB • Max 1 files
Detection Results
Overview
Understand what the tool solves, how it works, and the boundaries of its data.
Select one file to see a type inferred from its opening bytes, a MIME media type label, the filename and size, a short hexadecimal header, and a comparison with the filename extension. A MIME type such as image/png is a label for a media format; it is not a certificate that the file is valid or safe.
The check reads at most the first 32 bytes and compares them with a finite set of signatures and a few simple text prefixes. For example, the PNG signature begins 89 50 4E 47 0D 0A 1A 0A. Renaming a PNG to photo.txt does not change those bytes, so the inferred extension can disagree with the name. The signature and media type are useful clues, not a full parse of the file.
unknown with application/octet-stream means no current rule matched.Some formats share a container signature. A DOCX, XLSX, PPTX, APK, JAR, or ODT may be recognized at the outer level as ZIP; the check does not open the archive to confirm its internal structure.
Guide
Follow the workflow and verify inputs and outputs with practical examples.
Drop or select the file without changing its name first. The current selection limit is 100 MB.
Read the detected extension and MIME label, then look at the status beside them. For an unknown result, the signature table did not recognize the opening bytes.
Copy or inspect the displayed hexadecimal bytes if you need to compare them with a format specification. Keep the original file while you investigate a mismatch.
For example, a PNG renamed to logo.dat can still produce a PNG result and a mismatch status. A report.docx may show ZIP and match because ZIP is an accepted outer-container suffix; that does not validate the document contents.
Use cases
See how the tool fits into real work and everyday tasks.
If a file will not open or its extension looks unusual, compare the name with the inferred type before choosing a compatible application.
When a file is rejected by an upload form, the header and extension status can help distinguish a naming mismatch from a format the checker does not recognize.
Compare a known sample’s opening bytes with its filename suffix to see why names alone do not identify file contents.
Q&A
Find concise answers to common questions and confusing cases.
The formats can use ZIP as an outer container. This check reports that container signature and does not inspect the files inside it.
No. It means the filename suffix is compatible with a signature rule that matched near the beginning. A damaged or deliberately crafted file can still produce a matching result.
The current rules may not cover the format or signature variant, or the identifying bytes may not occur in the opening 32 bytes. Unknown does not mean the file has no format.
No. Its text rule only checks whether trimmed opening text begins with { or [; it does not parse the complete JSON document.
Notes
Review scope, result limitations, and important precautions before use.
Use this as a preliminary format clue. It is not malware scanning, file repair, authenticity verification, integrity checking, or a guarantee that an application can open the file.
Related
Discover related tools, collections, and available API capabilities.