What regex flavors are supported?

The visualizer supports JavaScript and PCRE-flavored regular expressions.

Can it identify named capture groups?

Yes, it lists and labels all capture groups, including named groups and their corresponding indices.

Does the tool support advanced PCRE features like recursion?

No, advanced features like recursive patterns, branch resets, and conditional groups are not supported and will return a parsing error.

How do I read the generated railroad diagram?

Read the diagram from left to right, following the paths through literals, branches, and loop-back arrows for repetitions.

Can I export the diagram?

Yes, the diagram is rendered as a standard SVG element that you can copy or save directly from your browser.

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Regex Railroad Diagram Visualizer

Render a regular expression as an SVG railroad (syntax) diagram showing literals, groups, alternations, and repetition, with capture-group numbering and flag explanations

Details

What this tool helps you do

Parses a JavaScript/PCRE-flavored regex with the ret library into an AST, then maps each node to a railroad-diagram primitive (rounded boxes for literals, labeled groups for captures, choice branches for alternations, loop-back arrows for quantifiers) rendered as SVG via railroad-diagrams. Also lists every capture group (with name) and explains each flag. Useful for teaching regex, documenting patterns, and spotting nested-quantifier backtracking risks.

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Samples

Regex Railroad Diagram Visualizer

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Key facts

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Examples

1. Visualizing a URL-matching regex

2. Deconstructing an Email Capture Pattern

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