Regex Tester Helper

Free Regex Tester Helper calculator with clear step-by-step results.

About Regex Tester Helper

Compiles a regular expression with the flags you select and reports how many times it matches the sample text, what the first match is, and how many capture groups the pattern defines. Invalid patterns are caught and reported rather than throwing.

Formulas

Flag construction

Flags = i when case insensitive, g when finding all matches

Group count

Capture groups are counted from the length of a match array against an always-matching variant of the pattern

Worked example

With the default values below, Regex Tester Helper returns Matches found of 0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Regular expression: \\b[A-Z][a-z]+\\b
Text to test against: The Quick Brown fox jumps over the Lazy Dog
Case insensitive: No
Find all matches: Yes

Results

Matches found: 0
First match: (no match)
Capture groups in the pattern: 0
Compilation status: Pattern compiled successfully

Step by step

1Values used
2Flag construction
3Group count
4Matches found= 0
5First match= (no match)
6Capture groups in the pattern= 0
7Compilation status= Pattern compiled successfully

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why does the global flag change the match count?

Without the global flag, matching stops at the first hit. With it, the engine continues scanning, which is why the count jumps from one to many on the same pattern.

Do capture groups include non-capturing groups?

No. Only numbered and named capture groups are counted; (?:...) groups affect precedence but capture nothing.