RegExr: Full Code Sense and Replace Support for RegEx Testing

This will be the last RegExr related post for awhile, I promise! I’m just having a lot of fun playing around with this.

I just uploaded version 0.2.1b of RegExr. This version includes support for using replace with regular expressions, including replacement codes (ex. $& is replaced with the RegExp match substring). Even better, I wrote a full RegEx lexer / tokenizer, so that RegExr understands the expressions you write at the token level. This allows it to provide accurate capturing group reports, nested token highlighting including display of errors, and contextual information on tokens as you roll over parts of your regular expression.

These new features make it way easier to learn regular expressions if you’re just starting out.

Here’s what the code sense looks like, notice the nested grey highlights:

And here’s the same view, but with a missing end bracket:

As always, you can use RegExr online at, or download the free AIR version for Mac OSX, Windows, and Linux at

Grant Skinner

The "g" in gskinner. Also the "skinner".



  1. I just want you to know that this program makes me so happy that i’m almost crying… i can feel the tears welling up… i have to go…

    Thx 🙂


  2. Just wanted to say what a brilliant application. Seems very simple upon first glance (I’m sure there’s a bit going on “under the hood” though), but extremely useful. Thanks for taking the time to write it and putting it out there to use.

  3. One of the really useful app on desktop…


  4. Do you have plans to open the source code?

  5. I found something strange, i’m using this expression to find unescaped commas in a string: /(?

  6. Avétis KAZARIAN March 5, 2009 at 5:26am

    I’m running a GNU/Linux x86_64 and I’ve got this error while trying to install the desktop version :

    “This application requires a version of the Adobe Integrated Runtime (AIR) which is no longer supported. Please contact the application author for an updated version.”

Comments are closed.