Testing Tools
Developer testing utilities for regular expressions. Build, test, and understand regex patterns with real-time feedback and plain English explanations.
Regex Tester
Test and debug regular expressions with real-time matching.
Regex Explainer — Plain English
Paste any regular expression and get a plain English explanation of what each part does.
Available Testing Tools
- Regex Tester — test and debug regular expressions with real-time matching and highlighting
- Regex Explainer — paste any regular expression and get a plain English explanation of what each part does
Working with Regular Expressions
A regular expression (regex) is a compact pattern for matching text — finding email addresses,
validating input, extracting fields from a log line, or running a search-and-replace across a
codebase. Regex is enormously powerful but notoriously hard to read: a pattern like
^\d{3}-\d{4}$ is quick to write and almost impossible to verify by
eye. The two tools here attack that problem from opposite directions.
Tester vs. Explainer — Which One?
- Regex Tester — use this when you're building a pattern. Type your regex and paste sample text; matches are highlighted in real time as you edit, so you can iterate until it captures exactly what you want and nothing more. It supports capture groups, flags, and shows what each match contains.
- Regex Explainer — use this when you're trying to understand a pattern someone else wrote (or that you wrote months ago). Paste any regex and it breaks the pattern into parts and explains in plain English what each token does — anchors, character classes, quantifiers, groups, and lookarounds.
A common workflow is to start in the Explainer to understand an existing pattern, then switch to the Tester to safely modify it against real sample data. Both tools use JavaScript's regular-expression engine and run entirely in your browser. To turn a shell glob into a regex, see the Glob to Regex converter.
Other Developer Tools
Frequently Asked Questions
- What testing tools does CodeTidy provide?
- CodeTidy offers a regex tester for building and debugging regular expressions with real-time matching, and a regex explainer that translates complex patterns into plain English descriptions. Both tools help developers work with regular expressions more effectively.
- How does the regex tester differ from the regex explainer?
- The regex tester lets you write a pattern and test it against sample text with real-time match highlighting. The regex explainer takes any regex pattern and breaks it down into a human-readable explanation of what each part does, making it easier to understand complex patterns.
- Do these tools support all regex flavors?
- The tools use JavaScript regular expressions, which support the most common regex features including character classes, quantifiers, groups, lookaheads, and lookbehinds. JavaScript regex covers the vast majority of patterns developers need.