How do I reference groups in a replacement?

Turn on Replace and use $1, $2 for numbered groups, $ for named groups, $& for the whole match and $$ for a literal dollar sign.

Do I need to escape forward slashes?

Not in this tester — the pattern box is passed straight to new RegExp(). You only need \/ when writing a regex literal like /a\/b/ in your code.

Is my test data sent to a server?

No. Matching runs entirely in your browser, so you can safely test patterns against logs or other private text.

🔒 Runs in your browser — nothing is uploaded✓ Free, no signup

Regex Tester — Test JavaScript Regular Expressions

Type a pattern and see every match highlighted as you type. Inspect capture groups, toggle flags and preview replacements — all in your browser.

Test string

Matches (2 found)

Contact ada@example.com or grace.hopper@navy.mil
Released 2026-10-09, patched 2026-11-01
Visit https://trueformatter.com/regex-tester from 192.168.1.20
Brand colors: #7c3aed and #fff

Match details

#	Match	Index
1	ada@example.com	8
2	grace.hopper@navy.mil	27

Replace

When should you use the Regex Tester?

Writing a validation pattern for emails, phone numbers or IDs
Extracting values from logs or text with capture groups
Checking a search-and-replace before running it on real data

How to use the Regex Tester

1
Enter a pattern
Type your regex in the pattern box without the surrounding slashes, or click a preset to start from a common pattern.
2
Pick flags
Tick g to find every match, i to ignore case, m for line-by-line ^ and $, s so . matches newlines, and u for Unicode.
3
Paste test text
Matches are highlighted on the right and listed with their index and capture groups below.
4
Try a replacement
Turn on Replace and use $1 or $<name> to rearrange matched text, then copy the result.

Examples

Named groups for dates

Pattern + text

/(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/g

Released 2026-10-09

Groups

match: 2026-10-09
year:  2026
month: 10
day:   09

Reformat with replace

Replacement

Pattern:     (\d{4})-(\d{2})-(\d{2})
Replacement: $3/$2/$1

Result

2026-10-09  →  09/10/2026

Common errors and how to fix them

Invalid regular expression: Unterminated group: A ( has no matching ). Close the group, or escape it as \( if you meant a literal parenthesis.
Nothing to repeat: A quantifier (* + ? {n}) has nothing before it, e.g. a pattern starting with *. Escape it as \* for a literal asterisk.
Only the first match is found: Turn on the g (global) flag.
^ and $ only match the whole text: Turn on the m (multiline) flag so they match at the start and end of every line.
. does not match across lines: Turn on the s (dotAll) flag, or use [\s\S] instead of the dot.

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Regex Tester FAQ

JavaScript (ECMAScript) regular expressions, using your browser's built-in RegExp engine. Results match what you get in Node.js, Chrome, Firefox and Safari.

g finds all matches instead of the first, i ignores case, m makes ^ and $ match at each line, s lets . match newlines, and u enables full Unicode matching including \p{...} property escapes.

Wrap part of the pattern in parentheses, e.g. (\d{4})-(\d{2}). Each group appears as its own column in the match details table. Name a group with (?<year>\d{4}) to see its name.

Turn on Replace and use $1, $2 for numbered groups, $<name> for named groups, $& for the whole match and $$ for a literal dollar sign.

Without the g (global) flag JavaScript stops after the first match. Tick the global checkbox to find every match.

Common causes are an unescaped special character such as ( [ { + * ? . or \, an unclosed group, or lookbehind syntax in an old browser. The error message under the pattern explains the problem.