Skip to content
WebToolShop WebToolShop

Regex Tester — free online tool

Test JavaScript regular expressions against sample log lines or form validation strings before deploying code.

When to use Regex Tester

Prototype email/phone validation patterns and see live match groups before shipping code.

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

What Regex Tester does not do

JavaScript regex flavour. Not PCRE/Python identical, and not a full regex101-style explainer (use Regex101 Lab for that).

How to use Regex Tester

  1. Type your JavaScript regular expression in the Regex Tester pattern field.
  2. Paste sample text in the subject input—log lines and form values work well.
  3. Run test to highlight matches and capture groups.
  4. Adjust flags (global, case insensitive) if the card exposes them, then retest.

Practical tips

  • Build the pattern incrementally—test each group before combining the full expression.
  • Remember this uses JavaScript regex; PCRE-only features like lookbehind vary by engine.
  • Escape literal dots and slashes, or they will match far more than you intended.

Example

Pattern ^[\w.-]+@[\w.-]+\.\w+$ against sample emails to see match vs fail.

Related tools on Webtoolshop

  • Regex101 Lab — Flags, replace preview, and a fuller lab when one line is not enough.
  • URL Encoder — Encode query values after you validate them with regex.

Limitations

Catastrophic backtracking can freeze the tab—test incrementally. Flags are JavaScript’s, not Python’s.

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 Regex Tester

What does the Regex Tester not do?

JavaScript regex flavour. Not PCRE/Python identical, and not a full regex101-style explainer (use Regex101 Lab for that).

Give me a concrete example for the Regex Tester.

Pattern ^[\w.-]+@[\w.-]+\.\w+$ against sample emails to see match vs fail.

Why did the Regex Tester 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 Regex Tester?

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.

Regular Expression Tester

JavaScript RegExp — matches listed below.

Copied!