MIME Type Lookup

How to Use the MIME Type Lookup

1. Type in the search box to filter the MIME database. Search matches against the extension (.pdf, pdf), the MIME type (application/pdf), or descriptive keywords (portable document).
2. Use the category pills - Application, Audio, Image, Text, Video, Font - to narrow the list to one top-level type.
3. Click a row to copy the MIME string to your clipboard in one click. An inline confirmation appears so you know it worked.
4. Scan the extensions column to see all file extensions commonly mapped to a given type (for example .jpg and .jpeg both map to image/jpeg).
5. Reach the reference anywhere - the entire dataset ships with the page and filter runs client-side, so it still works offline after first load.

How the Lookup Works

The table is generated from a curated JSON array combining the IANA Media Types registry, the Nginx mime.types file shipped with the server, the Apache httpd mime.types file, and a handful of community-tracked formats (AVIF, HEIC, WebP, opus). Every row is annotated with whether the format is a Structured Syntax Suffix (like +json, +xml, +zip) and whether it is a standards-track IANA assignment or a vendor tree entry. The filter uses a simple case-insensitive substring match over all fields, so a search like json surfaces application/json, application/ld+json, application/manifest+json, and half a dozen others. Everything runs in the browser via plain JavaScript array methods; there is no backend lookup, no external CDN fetch, and no analytics keystroke capture.

When You Would Use This Lookup

• Setting the Content-Type header correctly on an S3 or R2 upload - the default application/octet-stream causes browsers to download instead of displaying inline.
• Configuring nginx, httpd, or Caddy mime.types entries for a new file format your users are uploading.
• Writing an accept= attribute on a file-input element - the MIME type restricts what the file picker shows.
• Debugging a download that opens as a blob of garbage text because the server returned text/html instead of application/octet-stream for a binary.
• Writing a file-extension-to-MIME mapping for a custom file-storage service.
• Explaining to a product manager why image/heic attachments break for desktop browsers that have not implemented the codec.

Common Pitfalls and Edge Cases

• application/octet-stream as a default. It is the IANA-defined fallback for "arbitrary binary data" but browsers treat it as "download, do not render." Use it only when you genuinely do not know the type.
• text/plain with charset. The full header is Content-Type: text/plain; charset=utf-8; omitting the charset leads some older browsers to render as Latin-1 and mangle non-ASCII text.
• application/json charset parameter. RFC 8259 states that JSON is always UTF-8 and does not accept a charset parameter. Adding charset=utf-8 is technically wrong though widely tolerated.
• Vendor tree entries. Types like application/vnd.ms-excel or application/vnd.openxmlformats-officedocument.spreadsheetml.sheet are vendor-namespaced and long. Keep the exact spelling - typos silently fail.
• Structured suffix ambiguity. A custom type like application/vnd.api+json signals JSON serialization. Consumers must parse it as JSON after stripping the suffix; the Accept header negotiation for application/json may or may not match depending on implementation.
• Mime sniffing. Browsers may override the declared Content-Type by sniffing the response body (the X-Content-Type-Options: nosniff header disables this). Always send the correct type anyway.

MIME Type Background

MIME (Multipurpose Internet Mail Extensions) was introduced in 1992 by RFCs 1521 and 1522 to extend email beyond ASCII text. HTTP adopted the same system for content negotiation, and Media Types became the canonical name when RFC 2046 superseded the email-specific spec. RFC 6838 (2013) is the current Media Type Specifications and Registration Procedures RFC, and the IANA Media Types registry is the authoritative list. Each type has a top-level category (application, audio, example, font, image, message, model, multipart, text, video) and a subtype. Parameters attach with semicolons, most famously charset. Structured Syntax Suffixes (+json, +xml, +zip, +cbor) were added in RFC 6839 so consumers can treat a custom type as JSON-wrapped without knowing the specific subtype. Over 2,000 types are registered as of 2026.

Comparison to Alternatives

On the command line, file --mime-type /path/to/file sniffs actual file content using magic-number matching (via libmagic) and is the most reliable identifier for a file you have on disk. xdg-mime query filetype file does the same on Linux desktops. Node.js developers use the npm package mime or mime-types, which wraps the Nginx mime.types database for programmatic lookup. Python has mimetypes.guess_type() in the standard library. The Mozilla MDN Common MIME types page is a browseable reference that is better than IANA's raw registry for learning. Use this web tool when you need fast filter-driven lookup without opening a shell - especially handy when you remember part of a name and need to find the exact spelling.