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File Type Identifier

Find out what a file really is by reading its bytes, not its name.

  • Free
  • No signup
  • Nothing uploaded
  • No watermark

Read in this tab. The file is never uploaded — which is the point: you check a download precisely because you do not yet trust it.

How to Identify a File Type from Its Contents

File Type Identifier: before and after TEXT A YOUR INPUT FILE TYPEIDENTIFIER DONE A RESULT

A file called invoice.pdf might really be a program, a photo sent from a phone might have lost its extension, or a download might arrive with no extension at all. The name is only a label. This tool reads the first bytes inside the file, where most formats leave a recognisable signature, and tells you what the file really is.

You get the format’s name, its MIME type, the usual extensions and a note on how it was recognised. If the extension on the name disagrees with the contents, a warning says so. Only the start of the file is read, so even very large files are identified in a moment.

No software to install Free Works on any device

Steps to Reveal a File’s True Format

  1. 1. Drop the file

    Drag a file in, or tap the dashed area to browse for one. Every type and size is welcome, including files with no extension at all.

  2. 2. Read the verdict

    The header names the format and its MIME type, for example PNG image and image/png.

  3. 3. See how it was decided

    The table explains what the format is, which bytes identified it, its usual extensions, the size, the last modified time and the type your browser guessed from the name.

  4. 4. Heed any mismatch

    If the name says one thing and the bytes say another, an amber warning appears. Treat an unexpected executable with great care.

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What Is File Type Identification?

Most file formats begin with a few fixed bytes, often called file signatures. PDFs start with %PDF, PNG images with a fixed eight-byte signature, and ZIP files with the letters PK. Office documents, EPUB books and many others are ZIP containers underneath, so the tool looks inside for further clues. Reading these signatures is how operating systems and security tools decide what a file really contains.

Why Use File and Archive Tools?

A ZIP from a colleague, a download with no extension or a folder full of badly named files can stop work for a while. These tools unpack, identify, hash and rename files inside your browser, so nothing is uploaded to find out what it is.

“Know what a file is before you open it.”
  • Archives opened without software
  • Downloads checked with hashes
  • Duplicate files found
  • Big files packed smaller
  • Unknown files identified
  • Files renamed in bulk
  • Folders compared quickly
  • Contents never leave your computer

Popular Uses for ZIP and File Tools

These tools help with the small file puzzles that come up every week.

  • Opening RAR files See and extract what is inside an archive on a computer with no unzip program.
  • Checking a download Compare a file’s SHA-256 checksum with the one on the download page.
  • Mystery files Find the real type of a file that has lost its extension or has the wrong one.
  • Renaming photos Rename a folder of camera photos with dates or numbers in one go.
  • Clearing duplicates Find repeated files taking up space in a downloads or photos folder.
  • Sending many files Pack several documents into one ZIP so they travel as a single attachment.
  • Comparing folders See which files differ between a backup folder and the working copy.
  • Reading file details Check a file’s size, dates and hidden metadata before sharing it.

What the File Identifier Tells You

Format and MIME type

The plain name of the format and the MIME type a web server or email program would use.

Evidence shown

States which bytes at which position matched, so you can see the reasoning, not just the answer.

Extension mismatch warning

Flags files whose name disagrees with their contents, a common trick in phishing emails.

Fast on big files

Only the opening portion is read, so multi-gigabyte videos and disk images are identified instantly.

Useful file details

Size in bytes, last modified time and the browser’s own guess are listed together.

Why Use ToolXkit for File Type Identifier?

Your files stay with you

Everything runs inside your browser. Nothing you open or type is uploaded to a server.

Archive Tools for Different Users

Office workers

Open ZIP attachments and bundle reports together without extra software.

Developers

Check signatures, MIME types and hashes, and create TAR or GZIP files.

IT support staff

Identify strange files and verify downloads before installing anything on a machine.

Photographers

Rename shoots in bulk and find duplicates before backing up a card.

Students

Unpack course material and zip up project folders for submission.

Security-minded users

Check what a file really is before trusting its name or icon.

Best Times to Unpack or Check a File

File tools are useful when you are:

  • Opening an archive on a new computer
  • Verifying a software download
  • Stuck with a file that won’t open
  • Tidying a messy downloads folder
  • Emailing a folder of documents
  • Checking a backup is complete
  • Renaming lots of photos
  • Freeing space on a full drive

Tips for Unknown Files

  1. Be wary of any file that claims to be a document or picture but is identified as an executable. Do not open it.

  2. If a file has lost its extension, add the one listed under Usual extensions and it should open in the right program.

  3. Plain text formats such as CSV or code have no signature, so they may be identified only as text.

  4. A .docx, .xlsx or .apk is really a ZIP archive inside. The tool looks further into the container to tell them apart.

Frequently Asked Questions

Answers to common questions about this tool.

How can I tell what type a file is without the extension?

Drop it here. The tool reads the signature bytes at the start of the file and names the format, so a file with no extension or the wrong one is still identified correctly.

Is it safe to check a suspicious file here?

Yes. The tool only reads the opening bytes; it never opens or runs the file, and no copy leaves your computer. Checking the real type before opening a doubtful attachment is a sensible habit.

Why does it say the extension does not match?

The file’s name suggests one format but its bytes show another. Sometimes this is harmless, such as a JPEG saved as .png. Sometimes it is deliberate, such as a program disguised as an invoice.

What is a MIME type?

A MIME type is a standard label, such as application/pdf or image/jpeg, that tells browsers and email programs how to handle a file. Websites send it with every download.

Why is my file identified only as text?

Many text formats, including CSV, JSON, HTML and source code, have no fixed signature. When almost every byte is printable text and no known pattern matches, the tool reports it as text.

Can I open a RAR or 7z file without installing anything?

Yes. RAR Viewer and 7z Viewer show what is inside and let you save the files you need, all from the browser. This helps on office computers where you cannot install an unzip program.

What is a checksum and why check one?

A checksum is a short code worked out from a file’s contents. If your copy gives the same code as the one the publisher lists, the file arrived complete and unchanged.

Is there a size limit in File Type Identifier?

It depends on your device rather than on the site. Everything is processed in memory in the browser, so a computer handles bigger archives and folders than a phone does.

Is File Type Identifier free to use at work?

Yes. It is free for personal and work use with no account. Because files stay on the machine, it also fits workplaces that do not allow uploading documents to outside sites.

Further reading

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