Regex Tools

C Regular Expression Tester

C Regular Expression Tester approximates POSIX ERE/BRE regular expressions in your browser and shows a matching regcomp/regexec C snippet for reference.

Client-sideRuns entirely in your browser — your data never leaves your device.

C Regular Expression Tester is a free Regex Tools utility that runs entirely in your browser — nothing you enter is uploaded.

Test text
Matches




C — regcomp() / regexec()



  
How to use C Regular Expression Tester

  
    
      
  1. Start by adding the text you want to check into C Regular Expression Tester.
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  2. Set POSIX pattern, Mode so the output fits your use case.
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  3. Watch the output update instantly while you adjust the text.
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  4. Use Copy pattern to keep or reuse the result.
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About this tool

  
C Regular Expression Tester is a static, client-side tool with no backend. C Regular Expression Tester runs your pattern locally with the JavaScript engine and shows captures live.

  
Flags and group captures are surfaced so you can refine the pattern quickly. Nothing you enter is uploaded, and it keeps working offline once the page has loaded.

  
Frequently asked questions

  

      
What is C Regular Expression Tester for?
C Regular Expression Tester lets you check your input right in the browser using the POSIX pattern, Mode controls, with the result shown instantly and nothing uploaded.

      
Does C Regular Expression Tester cost anything?
No — C Regular Expression Tester is completely free, with no sign-up and no hidden limits.

      
Where is my data processed by C Regular Expression Tester?
Entirely in your browser — C Regular Expression Tester keeps your data on your own machine and sends nothing anywhere.

      
Which regex flavor does C Regular Expression Tester use?
C Regular Expression Tester runs your pattern with the browser's own JavaScript regex engine, live and on your device.

      
Does C Regular Expression Tester work offline?
Once the page has loaded, C Regular Expression Tester keeps working with no network connection.

  

  
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