File Type Checker
Drop in any file to identify its real type from magic bytes and structure — and see whether the extension and MIME type actually match. Nothing is uploaded.
Drop a file to identify it
Any file works — the type is detected locally in your browser.
Only the first 64 KB is read. Large files are never fully loaded or uploaded.
Select fileIdentify a file's real type without uploading it
This file type checker reads only the first 64 KB of your file with browser JavaScript and inspects its magic bytes (file signature) and internal structure to identify what the file really is. It then compares that against the file's extension and the MIME type your browser reports, so you can instantly tell whether a file is mislabeled, renamed, or exactly what it claims to be. The file itself never leaves your device.
Choose any file
Drag in a file or click to browse. Any format works — even files with no extension or a wrong one.
Detect locally
Your browser reads the first bytes and matches them against known file signatures and container structures.
Read the result
See the detected type, category, confidence, signature bytes, and any mismatch with the extension or MIME type.
There are several different ways to describe a file's type, and they do not always agree. This tool shows each layer side by side so you can see exactly which one is misleading you.
Extension
The text after the last dot in the file name, like .jpg or .pdf. It is just a label and can be renamed to anything, so it is the least trustworthy signal of what a file actually contains.
Browser MIME type
The MIME type (for example image/png) that your operating system or browser guesses, usually from the extension. It is convenient but is often wrong or empty for unusual files.
Magic bytes
A short signature at the very start of most binary formats — PNG, PDF, ZIP, MP4 and more each begin with a fixed byte pattern. This is the strongest, hardest-to-fake signal of a file's true type.
Container structure
Some formats share a wrapper. DOCX, XLSX, ODT and APK are all ZIP archives, so the tool peeks at internal entry names within the bounded prefix to subtype them precisely.
Real type, not just the extension
Detection is based on the actual file signature and structure, so a PNG renamed to .jpg or an EXE disguised as a PDF is identified correctly.
Mismatch warnings
When the extension or MIME type disagrees with the detected content, the tool shows a clear warning explaining the conflict.
No upload, fully private
Everything runs in your browser. The file is read in memory and never sent to a server, so confidential documents stay on your device.
No file size limit
Only a small bounded prefix is read, so multi-gigabyte files are identified just as quickly as tiny ones without loading them fully.
Dozens of formats
Images, documents, archives, audio, video, fonts, executables and clean-text formats like JSON, XML, HTML and CSV are all recognized.
Confidence and signature preview
Each result includes a confidence level and a hex preview of the leading signature bytes so you can verify the detection yourself.
Identify a file with no extension
Recover the real type of a downloaded or extracted file that lost its extension, so you know which app should open it.
Verify a suspicious attachment
Confirm that a file labeled as a document or image really is one, and catch executables or scripts hiding behind a safe-looking extension.
Debug uploads and conversions
Check what a tool actually produced or what a server received when a MIME type, import, or upload validation is failing unexpectedly.
The detector recognizes a wide range of binary signatures and falls back to clean-text structure analysis for plain-text formats. Coverage includes, but is not limited to:
Images
PNG, JPEG, GIF, WebP, BMP, TIFF, AVIF and HEIC/HEIF.
Documents
PDF, DOCX, XLSX, PPTX and OpenDocument ODT, ODS and ODP.
Archives & packages
ZIP, RAR, 7Z, TAR, GZIP, plus APK, WASM and Windows EXE.
Audio
MP3, WAV, FLAC, OGG and M4A/AAC.
Video
MP4, MOV, M4V, WebM, MKV and AVI.
Fonts & text
TTF, OTF, WOFF, WOFF2, and text such as JSON, XML, HTML, CSV and TXT.
Best for private, instant checks
Use this tool when you want to identify a file quickly without sending it anywhere, especially on a shared, work, or school device.
Why local detection is enough
Magic-byte detection only needs the first few bytes, so reading a tiny prefix in the browser is as accurate as a server scan for type identification.
When a deeper tool helps
For malware analysis, deep metadata extraction, or repairing corrupt files, use a dedicated forensic or command-line tool such as file(1) or a sandbox.
Files stay in your browser
The file is read in browser memory with JavaScript and is never uploaded. No file name, content, signature bytes, or extracted text is sent to analytics.
Bounded reads only
Only the first 64 KB is read. Container subtyping for ZIP-based formats inspects only that bounded prefix, so huge or corrupt archives fail gracefully instead of hanging.
Detection is a strong hint, not proof
Signatures can be spoofed and some formats share bytes, so a result is a high-quality guess. A clean type check does not by itself guarantee a file is safe to open.
Encrypted or unusual files
Encrypted, password-protected, or proprietary formats may be reported as a generic container or as unrecognized when no known signature is present in the prefix.
01Is my file uploaded anywhere?+
No. The file is read locally in your browser and never sent to AI Toolbox or any server. Detection happens entirely on your device.
02How does it identify the file type?+
It reads the first bytes of the file and matches them against known magic-byte signatures, then inspects container structure for ZIP-based formats. It also compares this with the extension and MIME type.
03Can it identify a file with no extension?+
Yes. Because detection is based on the file's actual bytes, it works even when the file has no extension or a completely wrong one.
04What is the file size limit?+
There is no limit. Only the first 64 KB is read, so even multi-gigabyte files are identified instantly without being fully loaded.
05Why does the extension not match the detected type?+
A file may have been renamed, exported incorrectly, or deliberately disguised. The tool flags this mismatch so you can trust the detected content over the label.
06What does the confidence level mean?+
High means a strong, unambiguous signature was found. Medium means a generic container or a likely text structure was inferred. Low means the result is based mainly on the extension.
07Why are DOCX and XLSX detected as ZIP archives?+
Office and OpenDocument files are ZIP containers internally. The tool peeks at internal entry names in the bounded prefix to report DOCX, XLSX, PPTX, ODT, ODS or ODP precisely.
08Does a clean result mean the file is safe?+
No. Identifying a file's type is not a malware scan. Signatures can be faked, so always treat unexpected files with caution even when the type looks normal.
09Which file types are supported?+
Common images, documents, archives, audio, video, fonts, and executables, plus text formats like JSON, XML, HTML and CSV. Unknown binary formats are reported as unrecognized.
10Does it work offline and on mobile?+
Yes. After the page loads, detection runs fully client-side, so it works offline and on modern mobile browsers as well as desktop.
Check a file type privately
Drop in any file and identify its real type locally in seconds — no upload, no signup.
Check a file nowThis tool runs client-side. Your browser reads a small prefix of the file in memory to detect its type; AI Toolbox does not upload, store, or log your files, file names, or contents.