Regex Tester lets you try a pattern against a sample string with flags so you can see matches before the expression lands in production validation code.
Enter Pattern, adjust Flags (default g), paste a Test string, click Test, and read the result panel. Iterate until capture groups behave.
Saves a round trip through unit tests for the first draft of an expression, though tests should still cover edge cases later.
What Regex Tester does
Evaluate regex patterns against sample input with flags.
- Pattern input
- Flags input defaulting to g
- Test string textarea
- Test action
- Result panel for matches or errors
Who Regex Tester is for
- Developers writing validation and parsing code
- Data cleaners extracting fields from logs
- SEO engineers crafting redirect rules
- Students learning regular expression syntax
How to use Regex Tester
1. Open Regex Tester on beeforge.dev.
2. Type the Pattern and set Flags as needed.
3. Paste representative text into Test string.
4. Click Test and refine the pattern based on the result panel.
Features
- Flag support including global matching defaults
- Immediate feedback loop for pattern drafts
- Error visibility for invalid expressions
- Local evaluation of sample text
- Companion diff tool when comparing replacement outputs
Examples
- Draft an email-like pattern and see false positives on a sample list.
- Test a log line extractor before dropping it into a shipping parser.
- Experiment with lazy vs greedy quantifiers on HTML-ish snippets.
Tips and limits
- JavaScript regex semantics may differ from Python, PCRE, or Go; confirm on your runtime.
- Catastrophic backtracking can freeze a tab; keep patterns and samples practical.
- Escape user input carefully when building regex dynamically.
- Prefer parsers for nested structures instead of heroic regex.
Related tools
- Diff Checker when you need to compare two replacement outputs line by line
- JSON Formatter when match results are JSON you want pretty-printed
FAQ
Which regex engine is this?
Browser JavaScript RegExp behavior. Port carefully to other languages.
Where is matching done?
In your browser. Sample text is not uploaded to BeeForge for testing.
Do flags support multiline?
Set flags such as m, i, and g according to what the Flags field accepts.
Can it do replace?
This UI focuses on testing matches. Perform replacements in your editor or code.
Why is there no match?
Check anchoring, flags, and whether you need raw strings without extra escapes.