Matches highlighted live
See exactly what your pattern matches in the test text as you type.
🧪
Regex Tester
Test a regular expression and see every match highlighted as you type.
🔒 Enterprise privacy — 100% client-side, no server uploads
Uses your browser's own JavaScript regex engine. Very complex patterns on very long text can be slow.
What is Regex Tester?
Regex Tester is a free online tool that lets you test a regular expression and see every match highlighted as you type. It works in your web browser with no signup. Enter your text or numbers and see the result instantly. Everything you type stays in your browser.
Also searched as: regular expression tester, regex checker, test regex online, regex match highlighter.
Regex Tester at a glance
- Price
- Free, with no paid plans
- Account
- No signup or login needed
- Where it runs
- In your web browser
- Your data
- Nothing you type is sent to a server
- Works on
- Any modern browser, on desktop and mobile
- Category
- Developer & Everyday Calculators
When to use Regex Tester
- →Check a pattern before using it in code
- →See every match highlighted as you type
- →Debug a regex that is not matching
How to use Regex Tester
- 1
Open Regex Tester and paste or type your text into the input box.
- 2
Your result updates instantly as you type — no button to click.
- 3
Adjust any mode or format options shown above the result, if the tool offers them.
- 4
Copy the output with one click, or leave it in place to keep editing.
Why use Regex Tester
- ✓Runs entirely in your browser — your file is never uploaded to a server.
- ✓No account, signup, or email address required to use it.
- ✓Completely free, with no daily limit and no signup.
- ✓Updates the result instantly as you type, so you can see changes in real time.
Regex Tester
Test regular expressions with live highlighting
Type a pattern and some text, and every match is highlighted as you type, with the flags you need and a clear message when the pattern is invalid.
Five flags
Use g for all matches, i to ignore case, m for multiline, s so the dot matches new lines, and u for unicode.
Clear errors
If the pattern is not valid, you get an error message instead of a blank result.
Safe on big text
The number of matches shown is capped at 500, so a pattern that matches everything cannot freeze the page.
Private
Your pattern and text stay in your browser.
Free, no signup
No account and no limit.
Everything you need in Regex Tester
- Live match highlighting
- Flags g, i, m, s and u
- Clear message for invalid patterns
- Match list capped at 500 for safety
- Runs in your browser
- Works on phone and computer
- No account needed
- Free to use
Tips for better results
- 1
Start simple
Build a pattern in small steps and check the highlighting after each change.
- 2
Use the g flag to see everything
Without g, only the first match is found.
- 3
Escape special characters
Characters such as . ? + * ( ) [ ] need a backslash before them if you mean the literal character.
0files uploaded
0signups needed
0cost to use
Tutorials on Regex Tester
Short, practical guides that go with this tool.
🔒 Your privacy with Regex Tester
Regex Tester runs as client-side JavaScript inside your own browser tab. Your file or text is read, processed, and turned into a result on your device — it is never sent to, stored on, or seen by Toolkitties' servers. Closing or refreshing the page clears everything.
Frequently asked questions
What do the flags mean?
g finds all matches, i ignores upper and lower case, m makes ^ and $ work on each line, s lets the dot match new lines, and u turns on unicode matching.
Which regex flavour does it use?
The tool uses JavaScript regular expressions, the same ones used in web browsers.
Why do I only see one match?
Turn on the g flag to find every match.
Why does it show an error?
The pattern is not valid, for example an unclosed bracket or a character that needs escaping.
Is there a limit on matches?
The tool shows up to 500 matches, which keeps the page responsive.
Is my text uploaded?
No. Everything runs in your browser.
Is Regex Tester free to use?
Yes. Regex Tester is 100% free, with no signup, no daily limit and no paid plans.
Do I need to create an account to use Regex Tester?
No signup or login is required. Open the page and start using Regex Tester immediately.
Is it safe to use Regex Tester with private or sensitive files?
Yes. Regex Tester processes your file locally in your browser using client-side code. The file itself is never uploaded to Toolkitties' servers.
Does Regex Tester store the text I enter?
No. Your text is processed in memory in your browser tab and is cleared as soon as you close or refresh the page.