Developer
Regex Tester
Use a regex tester to check patterns, flags, capture groups, and match results against sample text in the browser.
Regex workspace
Build, test, and explain a pattern in one place. Load a preset, refine the expression, and watch the matches update live.
Build the pattern
Start with the core expression, then add flags, groups, and repeats.
Regex examples
Pick a preset to load both the pattern and sample text.
Find each standalone word in a short block of text.
Pattern breakdown
A short explanation of what the current pattern appears to use.
Stores matched text so you can reuse or inspect it later.
Matches one character from a specific set or range.
Controls how many times the previous token can repeat.
Escapes special characters so they are treated literally.
Match preview
Watch the sample text update live as you refine the pattern.
alpha betagamma deltaWhy use a regex tester
A regex tester helps you check a regular expression before you wire it into code, validation rules, or search logic. It makes patterns, flags, and capture groups visible so you can spot mistakes quickly.
That makes the page useful for developers, QA work, and anyone searching for regex tester, regular expression tester, or regex checker with a practical preview of match results.
How regex flags change results
Flags control how a pattern behaves. Global mode finds every match, case-insensitive mode broadens the search, multiline mode changes line handling, dotAll lets dots span new lines, and unicode mode helps with broader character handling.
Seeing those flags in one place makes it easier to compare results and understand why a pattern behaves the way it does across different inputs.
Capture groups and debugging
Capture groups let you pull out specific parts of a match, such as IDs, words, or delimiters. A good regex debugger should show those captured values clearly so you can validate both the full match and the pieces inside it.
That is especially helpful when you are testing patterns for forms, text processing, or log parsing and want to see exactly what will be returned before you ship the rule.
How to build a regular expression
Start with the smallest useful pattern, then add anchors, groups, and quantifiers one step at a time. For example, match a word boundary first, then decide whether you need a capturing group or a non-capturing group, and only then add optional pieces or alternation.
The examples on this page give you a practical starting point for building a regex for words, email addresses, dates, quoted text, or hex colors. Load a preset, change the pattern, and use the live results to refine the expression before you copy it into code.
FAQ
What does this regex tester show?
It shows the compiled pattern, active flags, every match, and any capture groups found in the sample text.
Can I test regular expressions online?
Yes. You can paste a pattern, set flags, and review the match output directly in the browser.
Does it support invalid pattern checks?
Yes. If the expression cannot be compiled, the page shows a syntax error so you can fix the pattern before using it elsewhere.
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