Regex Tester Online: Test Regular Expressions in Real Time
Regex is very useful. Regex can also be hard to understand, make you angry, and make you want to scream. If you have a regex tester that highlights live, you can spend 5 minutes or 50 minutes on a pattern. As you type, you can see exactly what matches.
I write regex every week to check data, parse logs, and get text out of files. And I still use a tester every time. No one gets regex right the first time.
Why should you test regex by sight
Because you can't see regex errors. A pattern that "looks right" might match things you don't want or miss things you do. With live highlighting, you can see right away what matches and what doesn't. You change things, see what happens, and learn.
The feedback loop is the most important thing. Write a pattern, see it match in real time, change it, and do it again. It's much faster than writing regex in your code, running it, checking the output, going back to edit, and running it again. How to Use the Tester In the top field, type in your regex pattern.
Put your test string below it. Matches light up right away. The tool lets you see: All matches are shown in your test string. Capture groups: each group is shown separately with its contents.
Match details include the position, length, and content of each match. Flags let you switch between global, case-insensitive, multiline, and other options. Patterns That People Often Search For Everyone needs email validation, but no one wants to write it from scratch. Regex is best known for matching phone numbers, dates, URLs, and IP addresses.
The tool comes with a sidebar that shows you common patterns that you can use as starting points. A quick tip: Don't use a "perfect" regex to check emails. The official spec is very hard to understand. A simple pattern that catches 99% of real emails is better than a 500-character monster that is hard to keep up with.
Fixing Regex If your pattern isn't matching what you think it should, try making it simpler. Begin with the simplest version that fits something, and then add more complexity one piece at a time. It's easy to see when adding a new part breaks things with the live preview. Be careful with greedy and lazy quantifiers. .* matches as many characters as possible, while .*? matches as few characters as possible.
This difference is what causes 80% of the regex bugs I see. The regular expression tester works with JavaScript, Python, and Go code. Choose your language and test without worry.