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Setting the correct MIME type is essential for HTTP headers, file uploads, and email attachments, but remembering the exact standard type string for every file extension isn't practical. This tool looks up the standard MIME type for a file extension, or the reverse — the file extension(s) that correspond to a given MIME type.
How it works
Choose a lookup direction and enter either a file extension or a MIME type. The tool checks it against a built-in registry of common MIME type mappings and returns the matching result.
- Enter lookup direction.
- Enter extension or MIME type.
- Click Calculate to see your results.
Examples
Looking up .pdf
The file extension ".pdf" maps to the MIME type "application/pdf".
Who should use it
- Setting the correct Content-Type header for a file upload or download endpoint.
- Determining what file extension(s) to expect for a given MIME type in an API integration.
Industry applications
- Web development and API design
- Systems administration and email configuration
Advantages
- Supports lookups in both directions (extension to MIME, and MIME to extension).
- Covers the most common web, document, media, and font file formats.
Limitations
- Limited to a built-in registry of common formats — highly specialized or vendor-specific formats may not be included.
Common mistakes to avoid
- Including the leading dot inconsistently when entering a file extension — the tool accepts it either way, but be consistent in your own documentation.
- Assuming every possible file extension has a single, universally agreed-upon MIME type — some formats have more than one valid type in use.
Best practices
- When setting a Content-Type HTTP header for a file download, always use the standard MIME type for that file's actual format, not a generic fallback like "application/octet-stream," when the format is known.
Tips
- When building a file upload validator, check both the file extension and its declared MIME type together for a more reliable format check than either alone.