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File Extension Finder

Look up what an extension means, what opens it, and whether it is risky.

  • Free
  • No signup
  • Nothing uploaded
  • No watermark
  • .pdfPDF document

    Fixed layout that looks the same everywhere.

    application/pdf

    Opens with: Any browser, or a PDF reader

  • .docxWord document

    A ZIP archive of XML files.

    application/vnd.openxmlformats-officedocument.wordprocessingml.document

    Opens with: Word, Google Docs, LibreOffice

  • .docWord document (old)

    The pre-2007 binary format.

    application/msword

    Opens with: Word, LibreOffice

  • .xlsxExcel workbook

    A ZIP archive of XML sheets.

    application/vnd.openxmlformats-officedocument.spreadsheetml.sheet

    Opens with: Excel, Google Sheets, LibreOffice

  • .csvComma-separated values

    A table as plain text. No formatting, no formulas, no types.

    text/csv

    Opens with: Any spreadsheet or text editor

  • .jpgJPEG image

    Lossy compression — every save loses a little more.

    image/jpeg

    Opens with: Anything

  • .pngPNG image

    Lossless with transparency. Best for screenshots and graphics.

    image/png

    Opens with: Anything

  • .webpWebP image

    Smaller than JPEG or PNG at the same quality.

    image/webp

    Opens with: Modern browsers and editors

  • .heicHEIC image

    What an iPhone saves by default.

    image/heic

    Opens with: Apple devices; Windows needs an add-on

  • .svgSVG vector image

    Drawing instructions rather than pixels — scales to any size.

    image/svg+xml

    Opens with: Browsers, Illustrator, Inkscape

    Careful: SVG can contain scripts. Do not open one from an untrusted source in a browser tab that matters.

  • .mp4MP4 video

    The most compatible video container.

    video/mp4

    Opens with: Anything

  • .mp3MP3 audio

    Lossy audio. Universal support.

    audio/mpeg

    Opens with: Anything

  • .zipZIP archive

    Several files bundled and compressed.

    application/zip

    Opens with: Built into every operating system

  • .rarRAR archive

    Proprietary archive, often better compression than ZIP.

    application/vnd.rar

    Opens with: WinRAR, 7-Zip, The Unarchiver

  • .7z7-Zip archive

    Open format with very high compression.

    application/x-7z-compressed

    Opens with: 7-Zip, Keka, p7zip

  • .exeWindows program

    An executable program.

    application/vnd.microsoft.portable-executable

    Opens with: Windows

    Careful: Runs code on your machine. Never open one from an email or download you did not expect.

  • .jsJavaScript

    Code that runs in browsers and on servers.

    text/javascript

    Opens with: Any text editor

    Careful: A .js file sent as an attachment is almost always malware — Windows will run it on double-click.

  • .batBatch file

    A list of Windows commands.

    application/x-bat

    Opens with: Text editor

    Careful: Runs commands immediately on double-click. Read it first.

  • .shShell script

    A list of Unix commands.

    text/x-shellscript

    Opens with: Text editor

    Careful: Read before running — it has whatever permissions you do.

  • .isoDisc image

    A copy of a CD, DVD or installation disc.

    application/x-iso9660-image

    Opens with: Mount it, or use 7-Zip

  • .sqliteSQLite database

    A complete database in a single file.

    application/vnd.sqlite3

    Opens with: DB Browser for SQLite

  • .jsonJSON data

    Structured data, human readable.

    application/json

    Opens with: Any text editor

  • .xmlXML document

    Structured markup.

    application/xml

    Opens with: Any text editor or browser

  • .epubEPUB book

    A ZIP of HTML pages — reflows to fit the screen.

    application/epub+zip

    Opens with: Any e-reader, Apple Books, Calibre

  • .ttfTrueType font

    A desktop font.

    font/ttf

    Opens with: Install it, or open in a font viewer

  • .psdPhotoshop document

    Layered image with full edit history.

    image/vnd.adobe.photoshop

    Opens with: Photoshop, GIMP, Photopea

  • .apkAndroid package

    An Android app, packaged as a ZIP.

    application/vnd.android.package-archive

    Opens with: Android

    Careful: Installing one from outside a store bypasses every check the store makes.

How to Use the File Extension Finder Online

File Extension Finder: before and after TEXT A YOUR INPUT FILE EXTENSIONFINDER DONE A RESULT

File Extension Finder is a lookup, not a scanner: type an extension, a format name or a MIME type and read what that kind of file is, which programs open it, and a warning if it can run code on your machine. It covers the common ones people ask about, from .docx and .heic to .apk, .bat and .sh. No file is needed.

Looks up what an extension means, what opens it, and whether it is risky. The risky ones are worth knowing by sight — .exe, .scr, .js, .vbs and .lnk all execute, and an attachment using one of them is the oldest delivery method there is.

No software to install Free Works on any device

Step-by-Step Guide to Using the File Extension Finder

  1. 1. Choose a file or folder

    It is read in this tab and never uploaded.

  2. 2. The result appears as soon as it has been read

  3. 3. Copy or download whatever you need from it

Try it now

What is the File Extension Finder?

Looks up what an extension means, what opens it, and whether it is risky. The risky ones are worth knowing by sight — .exe, .scr, .js, .vbs and .lnk all execute, and an attachment using one of them is the oldest delivery method there is.

At a glance

  • Takes: An extension, format name or MIME type typed in
  • Gives: What it is, what opens it, its MIME type, and a risk note where one applies
  • Covers: 27 common types: documents, images, audio, video, archives, scripts, apps
  • Risky ones: .exe, .js, .bat, .sh, .svg and .apk carry a warning
  • Needs: No file and no upload

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 You Can Do with the File Extension Finder

Identifies a file by its actual signature bytes, not by trusting the extension

Hashes are computed over the whole file, so the value can be compared against a published checksum

Why Use ToolXkit for File Extension Finder?

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 and Good to Know

  1. It is a short list. An unusual extension such as .xcf or .parquet will return nothing; search the web for those.

  2. It does not look at any file. To learn what a file really is, drop it into File Type Identifier, which reads the bytes.

  3. The risk note is about the type, not a specific file. A .js attachment is dangerous in general; a .pdf can still carry a malicious link.

Frequently Asked Questions

Answers to common questions about this tool.

Do I need to install anything to use the File Extension Finder?

No. File Extension Finder runs entirely in your browser — there is nothing to download, no extension and no desktop program. It works the same on Windows, macOS, Linux, Android and iPhone.

Is it safe to use the File Extension Finder online?

Safer than the usual alternative, yes. Most online tools upload your file to a server you know nothing about, where it sits until someone deletes it. Here the file never leaves your device — the processing happens in the page itself, so there is no server copy to leak, retain or sell.

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 Extension Finder?

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 Extension Finder 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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