Interactive Regular Expression (RegEx) Tester
Test and debug JavaScript regular expressions in real-time with capturing group breakdown and live substitution.
How to Use Interactive Regular Expression (RegEx) Tester
1. Enter Regular Expression
Type your regex pattern and toggle flags (Global `g`, Case-Insensitive `i`, Multiline `m`, DotAll `s`).
2. Paste Sample Test Text
Provide sample test text to evaluate matching patterns and capture groups.
3. Inspect Real-Time Matches
Matches, indices, and capture groups highlight in real time, with an interactive replacement preview.
How This Utility Works
An interactive in-browser Regular Expression (RegEx) debugger. Tests patterns with all JavaScript flags (g, i, m, s, u), breaks down capturing groups and match offsets in real time, provides popular regex presets (emails, URLs, IPs, dates), and features a live substitution sandbox. 100% private and client-side.
Tokens, internal JSON payloads, and source code are parsed strictly inside your local browser runtime. Zero bytes are uploaded to remote servers.
Frequently Asked Questions
What regex engine does this tool use?
It uses the native JavaScript RegExp engine built into your web browser, ensuring 100% compatibility with modern ECMAScript standards.
How does the substitution feature work?
You can replace matched substrings using standard replacement tokens like $1, $2 for numbered capturing groups, or literal strings.
Can I test complex multiline text payloads?
Yes! Simply toggle the Multiline (m) or DotAll (s) flags to match patterns spanning across line breaks.
Test Regular Expressions in Terminal
Run directly in your terminal without installing external heavy dependencies
$ grep -P -o "^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}" file.txtPerforms Perl-compatible regular expression (PCRE) pattern matching and extracts matching tokens (-o).
$ python3 -c 'import re, sys; print(re.findall(r"\d+", sys.argv[1]))' "Found 42 items and 99 errors"Extracts regex matches using Python re module directly from the command line.