Regex Explainer
Break down a regular expression into plain-English token explanations. Quick reference for unfamiliar patterns.
| Token | Meaning |
|---|---|
| ^ | Anchor: start of line/string |
| \d | Any digit (0-9) |
| {3} | Repeated exactly 3 times |
| - | Literal '-' |
| \d | Any digit (0-9) |
| {4} | Repeated exactly 4 times |
| $ | Anchor: end of line/string |
About Regex Explainer
Pastes a regex and produces a token-by-token explanation: what each metacharacter does, what character classes match, where groups begin and end, what quantifiers apply. Useful for quickly understanding an unfamiliar regex or as a teaching aid.
When to use it
- Reading an unfamiliar regex from a codebase
- Teaching regex syntax to newcomers
- Sanity-checking that your pattern means what you think
- Documenting a regex with its plain-English meaning
How it works
The pattern is tokenized left-to-right and each token is matched against a table of common regex constructs: anchors (^, $), character classes (\d, \w, \s, [abc]), quantifiers (*, +, ?, {n,m}), groups (capturing, non-capturing, lookaround), alternation (|), and escape sequences. The explanation is best-effort — it won't catch every nuance of complex patterns.
Examples
^\d{3}-\d{4}$^ Anchor: start of line
\d Any digit (0-9)
{3} Repeated exactly 3 times
- Literal '-'
\d Any digit
{4} Repeated exactly 4 times
$ Anchor: end of lineFrequently asked questions
- Is the explanation perfect?
- It's heuristic. Common patterns are explained well; deeply nested or pathological patterns may not be fully described. For a guaranteed-correct explanation, walk through the pattern manually or use a visualizer like regexper.com.
- Does it explain my flags?
- No — the explanation focuses on the pattern itself. Flags (g, i, m, s, u, y) are listed in the regex-tester tool.