ByteScope

File Type Identifier

Find out what a file really is — magic-number detection, locally.

Your files never leave your browser — all processing is local.

Drop files here

or click to browse — batch identification supported, nothing is uploaded

About this tool

Drop any file — especially one with a missing, wrong or unknown extension — and this tool reads its first bytes (and, where needed, its tail) to identify the real format from magic-number signatures. You get the detected type, its MIME type, the correct extension, and a one-line explanation of what the format actually is. Everything runs in your browser; files are never uploaded, so it's safe for files you don't trust.

Extensions lie, and that's the point of this tool: a .jpg that is actually a PNG, an .exe hiding inside a renamed document, or a mystery download with no extension at all. When the detected type doesn't match the extension, the mismatch is flagged prominently with the suggested correct name. Container formats get a second look — docx, xlsx, pptx, apk, jar and epub are all ZIP files inside, so the tool opens the container's directory to tell them apart, and does the same for the RIFF family (WAV, AVI, WebP).

Text files get their own analysis: encoding (UTF-8/16, BOM presence), line endings (LF vs CRLF), and whether stray NUL bytes suggest binary contamination. Batch mode identifies many files at once, and anything unidentifiable shows its first 64 bytes as hex with a one-click jump into the Hex Editor for manual inspection.

Frequently asked questions

Is my file uploaded to identify it?
No. Only the first few kilobytes (and for some container formats, the tail) are read locally in your browser to match against the signature database. The file never leaves your device — which is exactly what you want when checking a suspicious file.
What is a magic number?
Most file formats begin with a fixed byte signature — PNG files start with 89 50 4E 47, ZIP archives with 50 4B. These "magic numbers" identify the real format regardless of the filename, which is how this tool (and the Unix `file` command) can catch a mislabeled file.
Why does my .docx show up as a ZIP file?
Because it is one — docx, xlsx, pptx, apk, jar and epub are all ZIP containers with specific contents. The tool looks inside the ZIP directory for telltale entries ([Content_Types].xml for Office, AndroidManifest.xml for APK) to report the specific format, not just "ZIP".
Can it tell me if a file is dangerous?
It can catch the common disguise trick — an executable renamed to look like a document — by revealing the true type. That's a useful first check, but it is not malware scanning: a genuinely-typed file can still contain malicious content.
What if the file can't be identified?
Unknown files show their first 64 bytes as hex so you can inspect the structure yourself, with a one-click handoff to the Hex Editor. Signatures are added over time, so unidentified formats are also a signal for us to extend the database.