Regex for File Extension
Extracts or validates file extensions.
Pattern
/\.[a-zA-Z0-9]{1,10}$/i Live Tester
Enter a string to test
Examples
The i flag makes the pattern case-insensitive.
✓ document.pdf
✓ image.png
✓ archive.tar.gz
✗ noextension
✗ file.
✗ .
Pattern Breakdown
\. — literal dot
[a-zA-Z0-9]{1,10}$ — 1-10 alphanumeric chars at end
Code Snippets
Javascript
"document.pdf".match(/\.[a-zA-Z0-9]{1,10}$/i)?.[0]; // ".pdf"Python
re.search(r"\.[a-zA-Z0-9]{1,10}$", "document.pdf").group() # ".pdf"Php
preg_match('/\.[a-zA-Z0-9]{1,10}$/i', "document.pdf", $m); // $m[0] = ".pdf"Related Patterns
Frequently Asked Questions
What is the regex for File Extension?▾
The regex pattern for File Extension is /\.[a-zA-Z0-9]{1,10}$/i. Extracts or validates file extensions.
How do I use the File Extension regex in JavaScript?▾
In JavaScript you create the pattern with a regex literal or the RegExp constructor and call .test() to check a string against it. A ready-to-copy example is shown in the Code Snippets section above, alongside Python and PHP versions.
What does the File Extension pattern match?▾
It matches strings like document.pdf; it rejects strings like noextension. See the Examples section above for the full list of matching and non-matching cases.