🔍 File MIME Type Checker
Check for mismatches between file extensions and MIME types. Helpful for identifying causes of "unopenable files" and format issues.
File signature analysis determines the true file format. Batch checking of multiple files is supported.
or click the button below to select files
💡 About MIME Type Analysis
• Browser Detection: MIME type determined by the browser when selecting the file
• Signature Analysis: Determining the actual format from the file's header byte pattern
• Extension Check: Comparison with the expected format based on the filename extension
If a mismatch is detected, the file may not open correctly.
❓ Frequently Asked Questions
Q: What is a MIME type?
MIME (Multipurpose Internet Mail Extensions) type is a standard way to identify file types. For example, JPEG files have the MIME type "image/jpeg" and PDF files have "application/pdf". Browsers and applications use MIME types to determine how to process files.
Q: Why do extensions and MIME types sometimes not match?
File extensions can be manually changed, so they may differ from the actual file format. For example, changing a JPEG file's extension to ".png" doesn't change the actual file content. Such mismatches can cause files to not open correctly.
Q: Why is there no clipboard paste function?
Due to browser security specifications, images pasted from the clipboard are automatically converted to PNG format regardless of their original format. Since this tool aims to check the true format of files, we haven't implemented the clipboard function which cannot provide accurate detection. To check the exact format of a file, please always select the original file directly.
Q: What is file signature analysis?
File signatures (magic numbers) are specific byte patterns at the beginning of files. For example, PNG files always start with "89 50 4E 47" and JPEG files start with "FF D8 FF". By analyzing these patterns, we can determine the actual file format regardless of the extension.
Q: What does "serious mismatch" mean?
This appears when the MIME type detected by the browser differs from the actual format determined by file signature analysis. For example, when a file with a ".jpg" extension is detected as "image/jpeg" by the browser but is actually a PNG file. In such cases, changing the file extension to the correct one may solve the problem.