File Info Checker
Local ProcessingShow a file’s size, extension, MIME type and modified time, and check the extension matches the content.
How It Works & Processing Standards
Show a file’s size, extension, MIME type and modified time, and check the extension matches the content.
Tool processing runs in your browser. If you create a calculator or conversion share link, its values are included in the URL. See the privacy policy for account, analytics and advertising data.
Current Limits
- Desktop max file size: 100MB
- Mobile max file size: 40MB
Choose mismatch check, size, extension, MIME or modified time under "Task". The mismatch check reads the first bytes to spot a PNG named .jpg or an executable with a renamed extension.
What You Can Do
- Extension/MIME mismatch
- Compares the content signature with the extension and MIME.
- Size, extension, MIME
- A table for several files at once.
- Modified time
- When each file was last modified.
How to Use File Info Checker
- 1Choose a taskPick the information you want.
- 2Select filesDrop several files if you like.
- 3Read the resultSee the details and verdict per file.
Examples
A renamed image
Input: photo.jpg (actually PNG)
Result: Verdict: extension mismatch
Sizes of several files
Input: 3 files
Result: A table of file names and bytes
Common Use Cases
- Checking an attachment you suspect is not what its extension says
- Testing whether an upload feature filters file types properly
Frequently Asked Questions (FAQ)
Does a mismatch mean the file is dangerous?
Not necessarily; wrong extensions are common after saving. But do not open an executable wearing a document extension.