How I look up MIME types when uploads or downloads behave oddly

A MIME type tells software what kind of content a file or response contains.

The MIME Types tool helps with the mechanical part, but I still check the result before using it somewhere real.

The simple idea

A MIME type tells software what kind of content a file or response contains.

I use the tool to make the transformation visible: input on one side, output on the other, and a quick sanity check before I copy anything.

Step 1: Search by file extension or MIME type

Search by file extension or MIME type.

Step 2: Compare the expected MIME type with the server Content-Type header

Compare the expected MIME type with the server Content-Type header.

Step 3: Check upload allowlists when a file is rejected

Check upload allowlists when a file is rejected.

Step 4: Remember file extensions can be misleading

Remember file extensions can be misleading.

Step 5: Use correct MIME types for downloads and APIs

Use correct MIME types for downloads and APIs.

Step 6: Do not rely on MIME type alone for security validation

Do not rely on MIME type alone for security validation.

Step 7: When serving files, set Content-Type deliberately

When serving files, set Content-Type deliberately.

My checklist

Before I trust the result, I check:

• Search by file extension or MIME type.
• Compare the expected MIME type with the server Content-Type header.
• Check upload allowlists when a file is rejected.
• Remember file extensions can be misleading.
• Use correct MIME types for downloads and APIs.
• Do not rely on MIME type alone for security validation.
• When serving files, set Content-Type deliberately.

Small utilities are useful because they remove repetitive work. They are safest when the output is still reviewed.