Regex Tester: free online, fast and secure
Regular expressions are powerful for validating input, searching logs and transforming text, but easy to get wrong. This tester highlights every match as you type, lists matches with positions and capture groups, and previews replacements.
It uses JavaScript regex syntax with flags like g, i, m, s, u and y.
How to use Regex Tester
- Enter a pattern and flags. For example [\w.+-]+@[\w-]+\.[\w.]+ with gi.
- Add test text. Matches highlight live.
- Inspect and replace. See groups and an optional replace preview.
Why use ConvertKaro Regex Tester? Free, fast and secure
There are many Regex Tester websites, but most of them upload your files, add watermarks or ask you to pay. Here is why this one is better.
100% Free
Regex Tester on ConvertKaro costs nothing. There is no trial, no premium plan and no hidden limit, so you can use it as often as you like.
Fast results
Because nothing travels to a server, results appear almost instantly. Large files are limited only by the speed of your own phone or computer.
Secure and private
Nothing is uploaded. Sensitive files like Aadhaar, PAN, salary slips or contracts stay on your own phone or laptop the whole time.
No signup, no watermark
No account, no email and no watermark on your result. Open the page and start.
Works on every device
Designed for mobile first, so it works just as well on your phone as on a desktop computer.
Live highlighting
Matches are marked in the text as you edit the pattern.
ConvertKaro vs other websites and apps
| ConvertKaro | Typical website or app | |
|---|---|---|
| Price | Free forever, every feature | Free trial, then paid plans |
| Your data | Stay on your device | Uploaded to a server |
| Signup | Not needed | Often required |
| Watermark or ads on result | Never | Common on free plans |
| Speed | Instant, no upload wait | Depends on upload speed |
| Daily limits | None | Usually limited |
Common uses for Regex Tester
- Validating emails, phone numbers and PIN codes
- Extracting data from logs
- Building find-and-replace patterns
- Learning regex
- Debugging form validation
Tips for the best results
- Indian mobile numbers: ^[6-9]\d{9}$
- PIN codes: ^\d{6}$
- Use $1, $2 in replacements to insert groups.
- Apply patterns to text with Find and Replace.
Good to know
Small utilities like Regex Tester save time every day: no need to open an IDE, install a package or write a script for a quick check. The tool follows the same standards used by browsers and Node.js, so results match what your code will do. Bookmark this page or add it to your home screen to keep it one click away.
| Price | Free, no limits |
|---|---|
| Processing | In your browser, instant |
| Signup | Not required |
| Watermark | None |
| Works on | Android, iPhone, Windows, Mac, Linux |
| Category | Developer tools |
How Regex Tester keeps your code and data private
Everything you enter into Regex Tester stays on your device. The tool works offline once the page has loaded, because all the logic is in the page itself rather than on a server. We never receive, log or store your code and data, so you can use it at work, at school or for personal matters without worrying about privacy.
Using Regex Tester on your phone
On a phone, open this page in Chrome or Safari, tap the main button and pick or paste what you need. Results download straight to your phone, usually into the Downloads folder or Files app. You can also add this page to your home screen for one-tap access next time.
Who uses Regex Tester?
Here are some of the people who find this tool most useful:
- Web developers and programmers
- Students learning coding and web design
- Digital marketers and SEO specialists
- Testers and support engineers debugging data
- Small business owners managing their own websites
Supported input: Plain text, JSON, CSS, JavaScript, HTML, URLs, Base64, tokens and image files where relevant.
Frequently asked questions
Which regex flavour is used?
JavaScript (ECMAScript), the same as in browsers and Node.js.
Why is my pattern invalid?
The error message explains the problem, often an unescaped bracket or slash.
How do I match a dot?
Escape it as \. because a plain dot matches any character.
Is Regex Tester really free?
Yes, completely free. You can use it as many times as you want, and every option on the page is included at no cost.
Is it safe to use Regex Tester online?
Yes. Your data are processed inside your own browser and are never uploaded to our servers, so nobody else can see them.
Does Regex Tester work on mobile?
Yes, the tool is built mobile-first. Open this page on your phone, add your data and download the result directly.
Do I need to install anything to use Regex Tester?
No. Regex Tester works in your web browser. There is no app, plug-in or extension to install.
Will ConvertKaro add a watermark or ask me to sign up?
No. There is no watermark, no login and no email required. Copy or download the result as it is.
Does Regex Tester work offline?
Once this page has finished loading, the tool keeps working even if your internet connection drops, because all processing happens on your device.
Related free tools
People who use this tool often need these too: Find and Replace, JSON Formatter, Text Compare, JavaScript Minifier, URL Encode Decode.