What flags are supported?

g (global — find all matches), i (case-insensitive), m (multiline — ^ and $ match line starts/ends), s (dotAll — . matches newlines), and u (unicode — enables full Unicode support).

How are matches highlighted?

All matches in the test string are highlighted in yellow. Capture groups are highlighted in distinct colors. The match list below shows each match's value, index, length, and captured groups.

What is the Replace field for?

Enter a replacement pattern in the Replace field to preview how String.replace() would transform the test string. Backreferences like $1, $2 refer to capture groups.

How can I test if a pattern is valid?

Invalid patterns show a red error message instantly. The pattern is wrapped in a try-catch so invalid regex syntax never crashes the tool.

Regex Tester

Test regular expressions against text with real-time match highlighting, group capture, and replacement preview.

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Regular Expression

//g

Test String

Replace with (optional)

How to Regex Tester

Type your regular expression pattern in the top field.
Enable or disable flags (g, i, m, s, u) using the checkboxes.
Paste your test string below to see matches highlighted in yellow.
The match list shows each match, its index, length, and any capture groups.
Optionally enter a replacement string to preview how .replace() would transform the input.
Use the quick reference panel to insert common patterns with one click.

Why Use This Tool?

Regex is one of the most powerful tools in a developer's toolkit, but testing patterns against real data in your IDE is slow. This tool gives you instant visual feedback — see every match highlighted, every capture group extracted, and the replacement output, all in real time.

Regex Tester

How to Regex Tester

Why Use This Tool?

Frequently Asked Questions