Test JavaScript regular expressions and inspect matches, positions and capture groups.
Enter the pattern without surrounding slashes and put flags in the separate field. g finds all matches, i ignores case, m enables multiline anchors, and s allows a dot to match line breaks.
[A-Z]([0-9]+) matches A102 and B203 in the example, capturing 102 and 203.
Uses JavaScript regular expression syntax. Positions are zero-based UTF-16 indices. Input is limited to 100,000 characters and results to 1,000 matches. A separate worker is stopped after one second to keep the page responsive.
Why does this differ from another language? Regex syntax and Unicode behavior vary across languages. This tool tests browser JavaScript behavior.