MIME Type Lookup

About this tool

MIME Type Lookup provides two-way lookups between file extensions and MIME content-type strings for 48 common file types across text, web, archive, image, audio, video, font and Office formats. Choose Extension → MIME and enter an extension like .mp4 or .wasm to get its MIME type, or choose MIME → Extension(s) and enter a type like image/jpeg to list the extensions that map to it. Input is case-insensitive and a leading dot is optional. The result is a single line such as mp4 -> video/mp4. This is handy for configuring server Content-Type response headers, writing upload accept attributes, and checking API file handling logic. Types outside the built-in table are reported as not found, so check the IANA registry for rarer formats. All lookups run locally in the browser — no file content is ever analyzed or uploaded.

Why use it

• Instant header values: Stop guessing Content-Type strings for formats like .wasm, .avif, or .heic — look them up in seconds and paste the correct value into your server config.

• Two-way lookup: Look up a MIME type from an extension or the extensions for a MIME type — switch with the Lookup Direction menu.

• Forgiving input: Extensions work with or without a leading dot and in any letter case, so .JPG, jpg and .jpg all give the same answer.

• Upload accept attribute helper: Building a file upload input? Look up the correct MIME type to use in the HTML accept attribute for browser-side file type filtering.

• Office format strings in one place: The long vendor types for .docx, .xlsx and .pptx are easy to mistype — copy them from the result instead.

• Runs locally: The extension table is built into the page, so lookups are instant and nothing you type is sent to a server.

How to use

1. Choose the Lookup Direction — Extension → MIME or MIME → Extension(s).
2. Type the file extension (with or without a leading dot, e.g. jpg or .jpg) or the full MIME string (e.g. image/jpeg) into the Search field.
3. Press Enter or click Lookup to retrieve the result.
4. Read the Result line, for example jpg -> image/jpeg or image/jpeg -> .jpeg, .jpg.
5. If you see 'No MIME type found' or 'No common extension found', the type is not in the built-in table of 48 extensions.
6. Select and copy the MIME string into your server config, code, or documentation; click Clear to start a new lookup.

When it helps

• Configuring a web server (Nginx, Apache, Caddy) and needing the correct MIME type string for a file extension to add to the mime.types file or config block.
• Writing an Express or FastAPI file-download endpoint and needing the exact Content-Type and Content-Disposition header values for a given file format.
• Building an HTML file upload form and needing the accept attribute values (e.g. image/webp,image/avif) for the file types you want to allow.
• Debugging a CDN or browser caching issue where assets are being served with the wrong Content-Type, causing incorrect rendering or CORS failures.
• Validating file-type restrictions in a backend API that must reject uploads unless the server-detected MIME matches an allowlist.
• Setting correct MIME types in an S3 bucket or Azure Blob Storage object metadata to ensure files are served correctly when accessed via direct URL.

Examples

Extension → MIME: .webp

webp -> image/webp

MIME → Extension(s): application/vnd.openxmlformats-officedocument.spreadsheetml.sheet

application/vnd.openxmlformats-officedocument.spreadsheetml.sheet -> .xlsx

MIME → Extension(s): image/jpeg

image/jpeg -> .jpeg, .jpg

Tips

• Always set an explicit Content-Type on API responses — never rely on Express or Flask auto-detection for file downloads, as it can default to application/octet-stream and break browser rendering.
• For the HTML file input accept attribute, combine MIME types and extensions for best cross-browser coverage: accept='image/png,image/jpeg,.png,.jpg' rather than relying on MIME types alone.
• When serving user-uploaded files, re-validate the MIME type server-side using magic-byte detection — do not trust the client-supplied Content-Type header.
• For SVG files, use image/svg+xml rather than text/xml or application/xml. Browsers require the image/ MIME type to render SVGs inline in <img> tags.
• text/csv should always be served with charset=utf-8 appended (Content-Type: text/csv; charset=utf-8) to prevent Excel from mis-detecting encoding on Windows.

Frequently Asked Questions

Glossary

MIME type

Multipurpose Internet Mail Extensions type — a two-part identifier (type/subtype, e.g. image/png) that describes the format of a file or data stream. Used in HTTP Content-Type headers, HTML accept attributes, and email attachments.

Content-Type header

An HTTP response header that tells the recipient what media type the response body contains. The browser uses it to decide whether to render, download, or pass the content to a plugin.

IANA media type registry

The Internet Assigned Numbers Authority's official catalog of registered MIME types. It is the authoritative source for standardized type/subtype strings and their associated file extensions.

Magic bytes

The first few bytes of a file that identify its format independently of the file extension. Libraries like libmagic use magic bytes for reliable format detection, unlike extension-based MIME lookup.

Vendor MIME type (vnd.*)

A MIME subtype prefixed with vnd. indicating a vendor-specific format registered with IANA — for example application/vnd.ms-excel for .xls files or application/vnd.api+json for JSON:API responses.

accept attribute

An HTML input attribute (used with type='file') that restricts the file picker to specific MIME types or extensions. It is client-side only and must be paired with server-side validation.