What is a regex railroad diagram?+
A railroad diagram (also called a syntax diagram) visualises the structure of a regular expression as a series of paths. Character literals appear as boxes, alternations (|) as branches, groups as nested regions, and quantifiers as loops or optional paths.
How do I debug a regex that isn't matching?+
Paste the pattern into the visualiser and trace the paths. Often a misplaced group or unescaped special character becomes obvious visually. Also check: is the character class correct? Is a quantifier greedy where it should be lazy?
Can the visualiser handle complex patterns?+
Yes - including named groups, lookaheads, lookbehinds, nested groups, alternations, and all standard character classes. Very long patterns may extend the diagram beyond the viewport; use scroll or zoom controls.
Does the visualiser support all regex flavours?+
The visualiser uses JavaScript regex syntax as the base. Most PCRE and Python re syntax is compatible. Flavour-specific features (e.g. Python's (?P<name>) named groups) are normalised for display.