Regex tester

Syntax and flags

The tester uses the JavaScript regular expression engine of your browser, the same one as Node.js and most front-end code. The g flag is always added so that every match is listed. Add i for case-insensitive, m so that ^ and $ match at each line, s so that . also matches newlines, and u for full Unicode. Named groups (?<name>...) and lookbehind (?<=...) are supported.

Reading the result

Each match shows its number, the line it starts on, its character index in the text and the matched text in quotes, so spaces and empty matches are visible. Capture groups follow, numbered from 1; a group that took part in no match shows "(not matched)". Results stop after 500 matches to keep the page responsive.

Replace preview

Type a replacement to see the whole text after replace. Use $1, $2 for numbered groups, $<name> for named groups and $& for the whole match. Other languages (Python, PCRE, Java) share most of this syntax, but details differ, for example named groups are written (?P<name>...) in Python.

Example

Finding ISO dates with three capture groups, then reformatting them with the replacement $3/$2/$1.

Input

/(\d{4})-(\d{2})-(\d{2})/
Order 2026-11-10 shipped
Invoice 2025-01-31 paid

Output

#1  line 1, index 6: "2026-11-10"
    group 1: "2026"
    group 2: "11"
    group 3: "10"
#2  line 2, index 33: "2025-01-31"
    group 1: "2025"
    group 2: "01"
    group 3: "31"

After replace:
Order 10/11/2026 shipped
Invoice 31/01/2025 paid

How to use

1. On the first line type the regex, for example /(\d+) items/i.
2. Paste the text to search below it.
3. Read the matches and groups. Optionally type a replacement to preview the replaced text.

FAQ

Why do I get many empty matches?

Your pattern can match zero characters, for example x* or \d*. Use + instead of * when at least one character is required.

Is my text sent anywhere?

No. The regex runs in your browser tab, so logs or data with personal information stay on your computer.

Does it support Python or PCRE syntax?

It uses JavaScript syntax. Most patterns are the same; check the details listed above when you move a regex to another language.

How do I match a literal slash or dot?

Escape it with a backslash: \/ or \. . A bare pattern on the first line (without surrounding slashes) does not need the slash escaped.