1. [Home](https://www.toolcomb.com/) 2. [Security Tools](https://www.toolcomb.com/security-tools) 3. MIME Type Lookup # MIME Type Lookup - Extension to Content-Type Reference Free MIME type lookup: map file extensions to Content-Type strings and reverse lookup by MIME. Eighty-plus common types for APIs, uploads, and CDN config - browser-only. ### Lookup Extension → MIME MIME → Extension File extension _png, pdf, webp…_ Type to search 95+ mapped extensions. ## What is a MIME type lookup tool? MIME types (Multipurpose Internet Mail Extensions media types) label the format of files and HTTP message bodies so browsers, APIs, and storage systems know how to handle bytes. When you upload avatar.png, the Content-Type might be image/png; when you fetch application/json, your client parses JSON instead of treating the body as plain text. A MIME type lookup tool maps file extensions to their usual MIME strings and supports reverse lookup when you only know the type from a response header. The IANA maintains the official registry, but day-to-day development relies on a stable subset: image/jpeg, text/html, application/pdf, video/mp4, and dozens of Office, archive, and font types. Servers choose Content-Type when serving static files; fetch and XMLHttpRequest expose the same value on responses. Mislabeled types cause broken previews (HTML served as text/plain), failed downloads, or CSP violations when inline scripts are blocked because the browser thought the resource was safe text. Extension-based guessing is heuristic. A file named report.pdf could still be malware renamed with a PDF extension; MIME labels describe intent, not authenticity. Conversely, some extensions map to multiple acceptable types (JPEG as image/jpeg vs image/pjpeg historically). This lookup uses common web and desktop conventions aligned with MDN and WHATWG guidance for static hosting and API design. Reverse lookup answers questions like “what extensions usually use application/vnd.openxmlformats-officedocument.spreadsheetml.sheet?” when you are writing Accept headers, configuring S3 metadata, or debugging a CDN that strips extensions. Copy buttons let you paste the exact string into curl, Postman, or Terraform aws_s3_object content_type fields without retyping long vendor-specific identifiers. Content negotiation (Accept and Accept-Encoding) sits beside MIME: clients advertise preferred types; servers pick the best match. While this tool does not negotiate, knowing the canonical type helps you craft Accept lists and validate that your API returns application/problem+json for errors instead of ambiguous text/html error pages from a reverse proxy. Multipart forms use MIME boundaries (multipart/form-data) where each part has its own Content-Type. File inputs rely on browser sniffing and the filename extension; server-side validation should still inspect magic bytes. Use this reference when documenting upload APIs or writing integration tests that assert Content-Type on fixtures. ToolComb’s MIME lookup runs entirely in the browser with a curated map of eighty-plus common extensions. No upload, no server round trip - suitable for quick checks on a laptop behind a corporate proxy. For exotic vendor types, cross-check the IANA registry; for production upload pipelines, combine extension hints with libmagic or file signature checks. S3 and GCS object metadata require accurate Content-Type for browser inline viewing. Uploading application/octet-stream forces download for PDFs users expect to preview. Lookup before setting metadata on CLI cp commands saves support tickets. Service workers and Workbox precache manifests sometimes hardcode URLs with wrong extensions after build pipeline renames. MIME mismatch breaks CSS when served as text/plain due to nginx default_types oversight - lookup helps write explicit types blocks. Email MIME trees (multipart/alternative) nest text/plain and text/html parts with boundaries distinct from file extension maps. This tool focuses on single-part file extensions; email engineers still use it for attachment filename to type mapping (.ics invites, .pdf invoices). .wasm modules require application/wasm for streaming compilation in modern browsers. Older tutorials omitted the type; lookup confirms the correct entry when configuring static hosts after Rust or Go compile steps. Security scanners flag SVG uploaded as image/svg+xml because embedded script tags execute in browser context. Knowing the MIME reminds developers to sanitize or serve SVG as attachment (Content-Disposition) when user uploads are allowed. API gateways validate Content-Type on ingress rules. Matching OpenAPI requestBody content types to real extension habits prevents 415 errors when mobile clients send image/jpeg for camera uploads but backend only declared application/json historically. Desktop Electron and Tauri apps serving local files must set MIME when registering custom protocols; wrong types break module workers and WebAssembly instantiation even though files load from disk without HTTP. Font MIME types (font/woff2, font/ttf) affect @font-face loading and CORS headers on CDNs. Lookup confirms whether your extension matches what Google Fonts or self-hosted nginx blocks expect. Archive types application/zip versus application/x-zip-compressed still appear in the wild; reverse lookup shows acceptable extension aliases when Windows explorers double-click behavior differs from Linux unzip CLI. JSON API responses should use application/json; some servers emit text/json historically. Aligning with application/json in OpenAPI reduces client parser warnings in strict HTTP libraries. ## How to look up MIME types and extensions Search by typing a file extension (with or without a leading dot) or a full MIME type string. Results update instantly on your device. 1. **Choose lookup mode** Use Extension → MIME for a file extension, or MIME → Extension when you have a Content-Type value. 2. **Enter your query** Type an extension such as jpg or .png, or a MIME type such as application/json. Matching is case-insensitive. 3. **Read the result row** Each result shows an extension and its associated MIME type. Multiple extensions can share the same type. 4. **Copy the value you need** Use the copy controls to put an extension or MIME type on your clipboard. 5. **Validate in your stack** Check the value in your server configuration or client code and verify it against a real response or upload. ## Example: PNG image upload ### Before You have dashboard-screenshot.PNG and need the Content-Type for a presigned S3 PUT URL. ### After Lookup png → image/png. Set Content-Type: image/png on the upload request so the object opens inline in browsers instead of downloading as octet-stream. If the CDN adds charset incorrectly, fix at origin - binary image types should not include charset parameters. ## When developers use MIME type lookup ### 1. Static site and CDN configuration Configure CloudFront, Netlify, or nginx mime.types so .webp serves as image/webp and .wasm as application/wasm for correct caching and security headers. ### 2. REST and GraphQL API design Document request and response Content-Type in OpenAPI. Return application/json for success and application/problem+json for structured errors. ### 3. Browser download and blob URLs When creating Blob or File objects in JavaScript, pass the correct type so save dialogs suggest the right extension and PDF viewers open inline. ### 4. Email and calendar attachments Map .ics to text/calendar and .eml alternatives; ensure mail clients display invitations and archives predictably. ### 5. Security review of uploads Compare declared Content-Type with extension during threat modeling. Note when image/svg+xml allows embedded script and requires sanitization. ### 6. Test fixtures and mocking Write MSW or Playwright handlers that return realistic Content-Type headers matching production APIs for faithful integration tests. ### 7. Kubernetes ingress mime types Ingress-nginx and Traefik use mime.types maps similar to standalone nginx. Lookup confirms whether uncommon extensions like .webp or .wasm need explicit entries before rolling out new static asset formats. ### 8. Desktop packaging pipelines Installers and auto-updaters set Content-Type on downloaded artifacts; wrong types trigger antivirus heuristics or block silent updates - lookup validates manifest metadata before release. ### 9. Headless CMS media library Editors upload mixed image and document formats; CMS stores extension and MIME together. Lookup reconciles user-renamed files where extension no longer matches stored Content-Type. ## MIME lookup vs server sniffing vs magic bytes Three layers often appear in upload pipelines. This tool covers the first; production systems combine all three. | Method | Input | Strength | Weakness | | --- | --- | --- | --- | | Extension map (this tool) | Filename suffix | Fast, human-readable | Spoofable rename | | HTTP Content-Type header | Client or server declared | Standard on wire | Can lie | | Magic byte sniffing | File contents | Detects true format | Heavier, needs libraries | | Browser MIME sniffing | Bytes + context | Forgiving for users | Historical XSS risks | Use extension and MIME tables for documentation and quick fixes; enforce content signatures on the server for untrusted uploads. ## Limits of this MIME reference - Curated list (~80+ entries), not the full IANA media type registry with hundreds of vendor-specific and obsolete types. - Does not include charset parameters (text/html; charset=utf-8) - append charset separately when configuring text responses. - Unknown extensions are not invented; search may return empty rather than guessing application/octet-stream. - Does not inspect file bytes - a .exe renamed to .png still maps to image/png by extension alone, which may be wrong for security. - New or regional formats may lag until the static map in this page is updated manually. - Content-Encoding (gzip, br, zstd) is orthogonal - gzip JSON remains application/json with separate encoding header. - Does not map Accept-Language or multipart boundary parameters - only single-type extension/MIME pairs. - Reverse lookup may list multiple extensions per MIME; pick the extension your platform documentation standardizes. ## Privacy Lookups execute locally in JavaScript against an embedded map. Search strings are not transmitted to ToolComb servers. Safe for querying proprietary vendor MIME strings from private APIs or internal file naming conventions. Copy actions use your local clipboard - other applications may read copied MIME strings; clear clipboard after handling confidential project codenames in filenames. No usage analytics record which extensions you searched; offline use works after initial page load. ## Frequently Asked Questions ### What is a MIME type? A MIME type (media type) labels the format of HTTP message bodies and files so clients choose parsers and viewers correctly - for example image/png for PNG images or application/json for JSON API payloads. It appears in Content-Type response and request headers. ### How do I find the MIME type of a file extension? Select Extension → MIME mode and type the suffix without the dot, such as pdf or webp. The table shows the common Content-Type string used on the web and in cloud object metadata fields. ### Can I look up extensions from a MIME type? Yes. Switch to MIME → Extension and type part of the type string like vnd.openxml or image/. Multiple file extensions may map to one MIME type - jpeg, jpg, and jpe all commonly map to image/jpeg. ### Is this the full IANA media type registry? No. ToolComb embeds eighty-plus frequently used web, office, media, archive, and font types. Vendor-specific, experimental, and obsolete IANA entries may be absent. Consult the official IANA registry for exhaustive legal type names. ### Should I trust file extension alone for security? No. Attackers rename malware to .pdf or .jpg. Production upload pipelines should validate magic bytes, scan content, and enforce size limits - extension lookup only documents expected Content-Type for honest filenames. ### Does Content-Type include charset? Text types are often served as text/html; charset=utf-8. This lookup shows the base type without parameters. Add charset separately in server config for HTML, CSS, JavaScript, and plain text to avoid mojibake. ### What is application/octet-stream? A generic binary fallback when no specific type is known. Browsers typically download rather than render inline. Prefer explicit types for PDF and images so users get inline preview when appropriate. ### Why do jpeg and jpg both exist? Historical filesystem conventions used both extensions for JPEG images. Modern servers should serve both with image/jpeg. The lookup lists aliases pointing to the same MIME entry. ### Is lookup data sent to a server? No. The embedded map and filter logic run entirely in your browser tab without uploading search terms. ### Is the MIME lookup free? Yes. Unlimited searches with no account or watermark. ### How do MIME types relate to Content-Disposition? Content-Type describes format; Content-Disposition inline or attachment influences whether browsers display or download. Pairing correct MIME with attachment can force download of SVG or PDF that might otherwise render inline with script risks. ### What about charset in text types? HTTP text responses should declare charset=utf-8 explicitly for HTML and JSON interoperability. This tool shows base MIME only - append ; charset=utf-8 in nginx, S3 metadata, or Express res.type calls. ## Related security and web tools - [Hash Generator](https://www.toolcomb.com/hash-generator) - Fingerprint file contents after verifying type. - [Base64 Encoder](https://www.toolcomb.com/base64-encoder) - Encode small text assets for data URLs. - [URL Parser](https://www.toolcomb.com/url-parser) - Inspect query strings on asset URLs. - [JWT Decoder](https://www.toolcomb.com/jwt-decoder) - Inspect Content-Type on token endpoints. ## Related Tools Discover more free tools that might help with your next task. 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