Skip to content
WebToolShop WebToolShop

Regex101 Lab — free online tool

Go beyond a simple match: see capture groups, try replace patterns, and skim a quick syntax reference for JavaScript regex.

When to use Regex101 Lab

A fuller regex lab when you need flags, explanations, and iterative testing beyond a one-line tester.

Useful when you want a quick answer without pasting sensitive data into random chat bots.

What Regex101 Lab does not do

Still JavaScript regex in the browser. Not a hosted regex101.com account or unit-test runner.

How to use Regex101 Lab

  1. Enter a regex pattern in the Regex101 Lab pattern box (JavaScript flavour).
  2. Add test text below and view match highlights and groups.
  3. Try replace preview if you are validating substitution syntax.
  4. Open the quick reference section on the page for anchors and quantifiers.

Practical tips

  • Use the replace preview to confirm a substitution before running it on real data.
  • Lean on the quick reference for tokens you forget, like \b word boundaries.
  • Patterns run in your browser with JavaScript regex—no PCRE-only syntax.

Example

Iterate a capture group with flags until the replace preview matches your log line.

Related tools on Webtoolshop

  • Regex Tester — Quick one-line test without the fuller lab UI.

Limitations

Richer tester still runs locally. Very large corpora are better in a desktop editor.

Privacy & data

We do not run a database on this static site. Text and generated output exist only in your tab until you close or refresh the page.

Frequently asked questions about Regex101 Lab

What does the Regex101 Lab not do?

Still JavaScript regex in the browser. Not a hosted regex101.com account or unit-test runner.

Give me a concrete example for the Regex101 Lab.

Iterate a capture group with flags until the replace preview matches your log line.

Why did the Regex101 Lab fail or look wrong?

Try a smaller file, fewer pasted characters, or an updated browser. Extensions that block scripts or downloads sometimes interfere—test in a private window if results never appear.

Does Webtoolshop store text I paste into the Regex101 Lab?

We do not run a database on this static site. Text and generated output exist only in your tab until you close or refresh the page.

Regex101-style Lab

JavaScript flavor: matches, groups, and replace preview. For PCRE / full debugger open regex101.com.

Inspired by regex101.com — this page runs regex in your browser only (no PCRE).

Matches

After replace

Quick reference (JavaScript) 
. any char   \d digit   \w word   \s space   ^ $ line bounds
+ * ? {} quantifiers   [] class   () group   | alternation
Use flag g for all matches, i case-insensitive, m multiline, s dotall
Copied!