What regex flavor does this tool use?
This tool uses the JavaScript (ECMAScript) Regular Expression engine, which is standard in all modern web browsers.
Is my data sent to a server?
No. All regex processing happens locally in your browser. Your patterns and test strings never leave your device.
What do the flags mean?
'g' finds all matches (global), 'i' ignores case, 'm' treats start/end characters as per line, and 's' allows dot to match newlines.
Does it support lookbehind?
Yes, if your browser supports it. Most modern browsers (Chrome, Firefox, Edge) support positive and negative lookbehind in JS regex.
Why isn't my regex matching anything?
Check your flags (e.g., enable 'i' for case variation) and ensure you've escaped special characters if needed. Also, verify your pattern syntax.
Can I use named capture groups?
Yes! JavaScript supports named groups like (?<name>...). They will appear in the match details.
How do I match a literal backslash?
You need to escape it with another backslash, like so: \\. In the regex input, you type just the pattern part.
Is there a limit on text size?
Performance depends on your device, but the tool is optimized for reasonably large text blocks. Extremely complex regexes on massive text may cause slowness.
How do I match a newline character?
Use \n to match a newline. If you want the dot (.) to match newlines, enable the 's' (dotAll) flag.
Can I copy the regex for use in my code?
Yes, click the 'Copy Regex' button to copy the pattern formatted with forward slashes and flags, ready to paste into your JavaScript code.