In demo site there are more engines (https://extendsclass.com/regex-tester.html), but in current source java-script engine available only.
I also noticed that other engines commented in index.html.
When trying to uncomment other engines a lot of 'self is undefined' errors occurs in developer's console.

i like to add some new lines and tabs to the Substitution text field.

but i tried \t and \\t and '\n' and \n\r but they not work there.

it would be nice if this would be possible.

Not sure this is a place to raise this issue. But it is the repo, where it has related to the test tools on https://extendsclass.com/.
In my side. It takes about more than two mins to show up the three editors-container

Thank you for making such a useful tool. Your visual explanation is the best one I've seen so far!

I found an edge case where the explanation does not work well. The RegEx matches correctly and the substitution also works well. Only the visual explanation is affected.

Given this RegEx: /(?<!=\s)useSelector\(/

And this string to test:

const isSidebarOpen = useSelector((state: RootState) => state.ui.sidebarOpen);

// ✅ DO (create the isSidebarOpenSelector in the proper file, then import it here)
const isSidebarOpen = useSelector(isSidebarOpenSelector);

const backdropAlpha = (100 - useSelector(getBackdropBrightnessSelector)) / 100;

The explanation does not render if there is a < character in the RegEx. If I delete <, it renders, but after I add it back, nothing happens.

i like on your site at most the graph showing me the structure of my regex (see https://extendsclass.com/regex/310af4e )

• but one drawback is to see results in the matching groups. for this i need to do something like this in the substitution textfield:

 (\$1="$1", \$2="$2", \$3="$3", \$4="$4", \$5="$5", \$6="$6", \$7="$7")

(but it shows nothing if i have more $n then matching groups exists)

but i like to see at your website better displaying of the matches like:

• here with colors in the matching text: https://regex101.com/r/HXg3iS/1 and the info when i hoover over it
• here i like the hoover over a text or the details tab below https://regexr.com/6pe5p