Why are all matches shown without checking a global flag?

This tool always scans the whole test string for the match list and find-and-replace, matching how most regex testers behave, since showing only the first match unless a specific checkbox is remembered is a common source of confusion. The i, m, s, and u flags still control real matching behavior.

Does find-and-replace change the original test string?

No, the result is shown separately so it can be compared against the original test string before copying it anywhere.

Is text pasted into the regex tester uploaded anywhere?

No. Matching and replacing both happen locally in the browser. Nothing typed in, including the pattern or test string, is sent to a server.

Regex Tester — Online Regular Expression Tester

Q: What regex flavor does this tool use?

The browser's native JavaScript regular expression engine, the same one used in Node.js and every JS-based application. It is similar to PCRE and Python's re module but not identical.

Pattern

Regular expression

i — ignore case m — multiline (^ and $ match line boundaries) s — dot matches newline u — unicode

Test string

Find & replace (optional)

Replace every match with

Frequently asked questions

Why are all matches shown even though I didn't check a "global" flag?

This tool always scans the whole test string for the match list and for find-and-replace, the way most regex testers do — showing only the first match unless you remember a specific checkbox is a common source of "why isn't this matching everything" confusion. The i / m / s / u flags above still control real matching behavior (case sensitivity, how ^/$ and . behave).

What regex flavor does this use?

Your browser's native JavaScript regular expression engine — the same one used in Node.js and every JS-based application. It's very similar to PCRE (used by PHP, and close to Python's re) but not identical; a pattern that works here should work in most JavaScript code, but double-check before relying on it in a different language.

Does find-and-replace change my original text?

No — it shows the result separately below, so you can compare it against your original test string before copying it anywhere.

Is my text uploaded anywhere?

No. Matching and replacing both happen locally in your browser — nothing you type in, including your pattern or test string, is sent to a server.