File Type & MIME Detector

About MIME Detector

File extensions are a naming convention, not a fact. This reads the first bytes of a file and matches them against known magic-number signatures — PNG, JPEG, GIF, PDF, ZIP, gzip, ELF, Mach-O, MP4, WebP, fonts and more — to report what the file actually is.

It is the quick answer when an upload is rejected as the wrong type, when a .csv from a client will not open, or when something downloaded with no extension at all.

Where it helps

• Identifies content regardless of what the file is named.
• Covers the common image, archive, document, media, font and executable formats.
• Only the beginning of the file is read, so it is instant even on large files.
• Entirely local — no upload, which matters for anything unidentified.

Limits

• Signature-based, so a format with no distinctive header — plain text, CSV, JSON — is reported only as textual.
• Modern Office documents and many others are ZIP containers, so they identify as ZIP.
• It reads the header, not the whole file: a valid header on a corrupt file still matches.
• Detection is not a safety verdict; a correctly identified file can still be malicious.

Frequently asked questions

Why does my .docx show as a ZIP archive?

Because it is one — Office Open XML documents are ZIP containers. The distinguishing content is inside, past the header this reads.

Why is my CSV reported as plain text?

CSV, JSON and other plain-text formats have no magic number. There is nothing in the bytes to distinguish them.

An upload was rejected as the wrong type — will this tell me why?

Usually. Servers check the real content, so a .jpg that is actually a PNG gets refused. This shows the mismatch.

Can it tell me whether a file is dangerous?

No. It identifies the format. Use antivirus tooling for safety questions.

Related tools

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• Image Converter — Convert between PNG, JPEG, JFIF, WebP, GIF, HEIC and SVG
• PDF Password Remover — Strip the password from a PDF you can already open
• Base64 — Encode or decode UTF-8 text and URL-safe Base64
• Icon Font Generator — Build a web font from SVG icons or an SVG font
• Image Resizer — Resize to a size, a proportion or a longest side

More Images & Files tools

• Icon Font Generator — Build a web font from SVG icons or an SVG font
• Image Converter — Convert between PNG, JPEG, JFIF, WebP, GIF, HEIC and SVG
• Image Resizer — Resize to a size, a proportion or a longest side
• Crop Image — Cut a rectangle out, or trim a flat border away
• Rotate Image — Turn by a right angle or any angle, and flip
• Image Base64 Converter — Turn an image into a data URI for CSS or HTML, and read one back
• WebP Converter — To WebP for the web, or back out of it
• SVG Converter — Draw an SVG at any size, or wrap a bitmap in one
• Background Remover — Take a flat background out and keep the subject
• Image Compressor — Resize and re-encode images to save bytes
• Image Optimizer — Strip metadata and redundant markup without touching the picture
• Favicon Generator — Build favicon PNGs and a multi-size .ico
• File Checksum — Verify a download, and work out which algorithm made the checksum
• QR & Barcode Reader — Read a code out of an image, and say what it does before you follow it
• Office Password — Protect a Word, Excel or PowerPoint file with a password
• Office Password Remover — Remove the password from a Word, Excel or PowerPoint file
• Image Editor — Crop, straighten, adjust and cut out, with every step visible and reversible
• Passport Photo Maker — Passport and visa photos at each country's size, with head guides and a print sheet
• PDF Editor — Move and retype what is already on the page, reorder, annotate, stamp and sign, with the document in front of you
• PDF Viewer — Read, search and inspect a PDF without leaving the browser
• PDF Password & Permissions — Lock a PDF with AES-256, and say what a reader may print, copy or change
• PDF Password Remover — Strip the password from a PDF you can already open
• Merge PDF — Join several PDFs into one document
• Split PDF — Cut a PDF into separate documents
• Delete PDF Pages — Remove pages from a PDF and keep the rest
• Rearrange PDF Pages — Put a PDF's pages in a different order
• Rotate PDF — Turn a PDF's pages the right way up
• Compress PDF — Make a PDF smaller, by rebuilding it or redrawing it
• Watermark PDF — Stamp text or a logo across a PDF's pages
• Sign PDF — Put a signature and a date onto a PDF
• Edit PDF — Add text to a PDF page, and hide what is underneath
• PDF to Images — Turn every page into a PNG, JPG, WebP, GIF or JFIF
• OCR PDF — Read the text off a scanned PDF
• PDF to Word — Turn a PDF into an editable .docx that keeps its layout
• PDF to Excel — Pull a PDF's tables into a .xlsx workbook that keeps their formatting
• PDF to PowerPoint — Turn a PDF's pages into editable .pptx slides that look the same
• Word to PDF — Turn a .docx document into a PDF that looks the way it does in Word
• Excel to PDF — Print a .xlsx workbook to PDF with its formatting and page setup
• PowerPoint to PDF — Turn a .pptx deck into a PDF that looks the way the slides do
• Images to PDF — Turn photos or scans into one PDF document
• PDF to Text — Pull the text out of a PDF as plain text
• Crop PDF — Trim the margins off every page
• Page Numbers — Number the pages of a PDF
• Header & Footer — Put a running head or foot on every page
• Bates Numbering — Stamp sequential legal numbers across pages
• Reverse Pages — Flip a PDF's page order end to end
• Add Blank Pages — Insert empty pages anywhere in a PDF
• N-Up PDF — Put several pages on one sheet
• PDF Booklet — Reorder pages for folded booklet printing
• PDF Metadata — Read, change or strip a PDF's properties
• Flatten PDF — Make form answers part of the page
• Alternate & Mix Pages — Interleave two PDFs a page at a time
• PDF Overlay — Draw one PDF over or under another
• Combine to Single Page — Stack every page into one continuous strip
• Divide Pages — Cut every page in half or into quarters
• Posterize PDF — Tile a large page across several printable sheets
• Fix Page Size — Put every page onto one uniform sheet
• Page Dimensions — Measure every page, its rotation and its sheet
• Rotate by Any Angle — Turn pages by a fraction of a degree or more
• Remove Annotations — Strip comments, highlights, links and stamps
• PDF Attachments — List, extract, add or remove embedded files
• PDFs to ZIP — Package several PDFs into one archive
• PDF Bookmarks — Read, write or remove a PDF's outline
• Table of Contents — Build a contents page from the bookmarks
• Page Labels — Number front matter in roman and the body in arabic
• Sanitize PDF — Strip scripts, actions, attachments and metadata
• Extract Images — Pull every embedded picture out of a PDF
• Extract Tables — Turn a PDF's tables into CSV, JSON or Markdown
• PDF to Markdown — Convert a PDF into Markdown with its headings, emphasis, lists, tables and pictures
• PDF to JSON — Export a PDF's text as structured JSON
• Compare PDFs — See which pages of two PDFs differ, and by how much
• Remove Blank Pages — Find the empty pages, and take them out
• Invert PDF Colours — A dark-mode version of a document
• PDF to Greyscale — Convert every page to shades of grey
• Adjust PDF Colours — Brightness, contrast and saturation across a document
• Scanner Effect — Make a clean PDF look like a photocopy
• PDF Background Colour — Tint the paper behind the content
• Rasterize PDF — Flatten every page into a picture of itself
• PDF to CBZ — Turn a PDF into a comic book archive
• CBZ to PDF — Turn a comic book archive into a PDF
• Text to PDF — Set a plain text file as a document
• Markdown to PDF — Set Markdown as it renders: headings, emphasis, lists, code, quotes and tables
• JSON to PDF — Print a JSON file as an indented tree
• CSV to PDF — Set a spreadsheet export as a printed table
• XML to PDF — Print an XML document as an indented tree