Instant header values
Stop guessing Content-Type strings for uncommon formats like .wasm, .avif, or .jsonld — look them up in seconds and paste the correct value into your server config.
UtilityKit
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MIME Type Lookup
Find MIME types from extensions and reverse-map MIME to extensions.
About MIME Type Lookup
MIME Type Lookup provides bidirectional lookups between file extensions and MIME content-type strings, covering the full IANA media type registry across application, audio, font, image, model, text, and video categories. Enter a file extension like .mp4 or .wasm and get the canonical MIME type, charset recommendations, and any common aliases. Reverse-lookup a MIME type like image/webp to discover associated extensions and know when a browser will render inline versus prompt a download. This tool is invaluable for configuring server Content-Type response headers, defining upload accept attributes, debugging CDN cache rules, and validating API file handling logic. All lookups run locally in the browser — no file content is ever analyzed or uploaded.
Why use MIME Type Lookup
Bidirectional lookup
Look up extension from MIME or MIME from extension — the only direction that matters is the one you need right now, and both are equally fast.
Inline vs download behavior
Know ahead of time whether a browser will render a MIME type inline (like text/html or image/png) or force a download (like application/octet-stream), preventing UX surprises.
Upload accept attribute helper
Building a file upload input? Look up the correct MIME type to use in the HTML accept attribute for reliable browser-side file type filtering.
CDN and cache rule validation
CDN platforms like Cloudflare and AWS CloudFront route and cache based on Content-Type — verify the correct MIME before writing cache rules or origin response transformations.
No internet required
All mappings are bundled in the tool. Works offline, inside Docker builds, or on air-gapped workstations — anywhere you need a quick reference.
How to use MIME Type Lookup
- Select the lookup direction — Extension to MIME or MIME to Extension — using the toggle at the top.
- 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.
- Press Enter or click Look Up to retrieve the result.
- Review the canonical MIME type, any known aliases, charset recommendation, and whether the type is typically rendered inline or downloaded.
- For MIME-to-extension reverse lookup, inspect the list of all associated extensions and click the one you want to copy.
- Use the Copy button to copy the MIME string directly to your clipboard for pasting into server configs, code, or documentation.
When to use MIME Type Lookup
- 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 to MIME
Input: Extension: .webp
Output: MIME type: image/webp | Inline rendering: Yes | Charset: N/A | No legacy aliases
Reverse MIME to extension
Input: MIME type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
Output: Extensions: .xlsx | Category: application | Inline: No (download) | Common name: Excel 2007+ Workbook
Font MIME lookup
Input: Extension: .woff2
Output: MIME type: font/woff2 | Legacy alias: application/font-woff2 | Inline: N/A (font resource)
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
What is the difference between application/octet-stream and a specific MIME type?▾
application/octet-stream is the generic binary fallback — browsers treat it as an unknown download and will not attempt to render it. A specific MIME type like application/pdf tells the browser (and downstream tools) the exact format, enabling inline rendering, syntax highlighting, or type-specific handling.
Can I include the leading dot when entering an extension?▾
Yes. The tool normalizes input, so .jpg, jpg, .JPG, and JPG all resolve to the same result. Case is ignored.
Why does one MIME type map to multiple extensions?▾
Some formats have been standardized under a single MIME type but have accumulated multiple common extensions over time. For example, image/jpeg maps to .jpg, .jpeg, and .jpe. The tool lists all registered aliases so you can choose the one your platform expects.
Does the tool detect MIME type from actual file content (magic bytes)?▾
No — this is a map-based lookup only. For magic-byte detection (sniffing), you need a server-side library like file-type (Node.js) or python-magic. Extension-based lookup is still the correct approach for generating Content-Type headers on known file types.
What MIME type should I use for JSON API responses?▾
Use application/json for standard REST APIs. For JSON-LD (linked data), use application/ld+json. For JSON:API compliant responses, the correct type is application/vnd.api+json.
What is the correct MIME type for WebAssembly?▾
The IANA-registered MIME type for WebAssembly is application/wasm. Some older server configs default to application/octet-stream for .wasm files, which still works but prevents some browser optimizations. Update your server config to serve .wasm with application/wasm.
Is the database based on the IANA registry?▾
Yes. The mappings are derived from the IANA media type registry and the Apache mime.types file, which is the most widely deployed reference for extension-to-MIME mapping in web servers.
Does it cover font MIME types for web fonts?▾
Yes. font/woff, font/woff2, font/ttf, font/otf, and font/collection are all included. Note that older browsers may expect application/font-woff — the tool flags this legacy alias.
Explore the category
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.