How does it determine the real file type?

It reads the file's magic bytes — a short signature at the start of the file that's specific to each format — rather than trusting the file extension.

Can this catch a file that's been deliberately mislabeled?

Yes, that's exactly the case it's built for — a renamed extension doesn't change the actual byte signature, so the true type is still detectable.

Does it work on files with no extension at all?

Yes, since detection is based on file content, not the name — a file with no extension is identified the same way as one with an incorrect one.

Does File Type Detector upload my files to a server?

No. File Type Detector runs entirely in your browser using on-device processing, your files never leave your device.

File Type Detector

Detect a file's true type from its byte signature, not just its extension.

Runs in your browser

Drop any file to detect its type

Choose File

About this tool

A file's extension is just a naming convention — nothing stops a file from being renamed to .jpg while actually being a PDF, either by accident or design, and an incorrect extension means the wrong app tries to open it. This tool reads a file's actual byte signature (the "magic bytes" at the start of the file that identify its real format) rather than trusting the extension, so you can confirm what a file actually is, useful for verifying downloads or investigating a file with a suspicious or missing extension.

Frequently asked questions

Hex Viewer

View the raw bytes of any file as a hex and ASCII dump.

File Metadata Viewer

View a file's name, size, type and last-modified date.

Zip & Unzip Files

Combine files into a ZIP archive, or extract files from one.

File Size Converter

Convert between bytes, KB, MB, GB, and their binary (KiB/MiB/GiB) equivalents.

Duplicate File Finder

Find identical files among a batch by comparing their content hash.

Batch File Renamer

Rename many files at once using a pattern, and download them as a ZIP.

File Extension Changer

Rename a file's extension without converting its actual format.

File to Base64 Converter

Encode any file as Base64, or decode Base64 back into a downloadable file.

GZIP Compressor

Compress or decompress a file using GZIP.

File Checksum Verifier

Verify a downloaded file against a published SHA checksum.

Archive Format Converter

Convert between ZIP and uncompressed TAR archives.

New

File Preview Viewer

Preview images, text, PDF, audio and video files instantly, without uploading them anywhere.

PDF Tools

Merge, split, compress and convert PDF files.

Image Tools

Compress, resize, crop and convert images.

Link & QR Tools

Shorten links and generate QR codes and barcodes.

Audio Tools

Convert audio files and turn text into speech, or speech into text.

Video Tools

Compress and process video files, right in your browser.

Developer Tools

JSON, encoding, hashing and text utilities for developers.

SEO & Web Tools

Meta tags, sitemaps, schema markup and other on-page SEO utilities.

Data & Spreadsheet Tools

Clean, convert and inspect CSV, TSV and tabular data.

Business Tools

Invoices, quotations, receipts and other business documents.

Social Media Tools

Resize images for social platforms, count hashtags and preview posts.