MIME Type Lookup Guide
Reference for checking common MIME types before setting headers, validating uploads, or documenting file handling behavior.
Quick answer
Use MIME Type Lookup when you need the expected media type for a file extension, upload rule, HTTP header, documentation note, or test fixture. It is a reference step, not a full file security scanner.
Step-by-step use
- Enter a file extension or MIME value.
- Review the matching type.
- Compare it with the server header or upload policy.
- Use HTTP Header Parser when debugging a real response.
- Document any exceptions your app allows.
Example
If a server sends a JavaScript file as text/plain, browsers may treat it differently from text/javascript. Looking up the expected type helps explain why a resource fails or triggers a warning.
Assumptions and limits
File extension and MIME type are only signals. They do not prove a file is safe, valid, or actually matches its content. Security-sensitive upload handling should inspect file content and enforce server-side rules.
Review example
For an upload rule, look up the expected MIME type, then compare it with the server-side validation rule and the actual response header for a known file. Document whether the rule is about preview behavior, download behavior, or accepted upload formats. Do not treat the lookup as proof that a user-provided file is safe.
When documenting a public API, include the allowed extension and expected content type in the same row. That helps frontend testers reproduce errors without exposing uploaded file names or private sample files.
Common mistakes
Trusting extensions alone. A renamed file can still contain unexpected content.
Treating lookup results as security validation. Use proper server-side checks for uploads.
Forgetting charset. Text responses may also need charset decisions.
Next steps
- HTTP Header Parser — inspect response headers
- File Hash Checker — compare downloaded files or build artifacts
- JSON Validator — validate MIME maps stored in config