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Test Python regular expression patterns online. Get real-time match results, capture groups, and position info to quickly debug text processing rules.
re.I / i
re.M / m
re.S / s
re.X
re.A
Please enter a regular expression and text to match
Overview
Understand what the tool solves, how it works, and the boundaries of its data.
Enter a regular-expression pattern and sample text to see matching text highlighted, a match count, and capture-group details. Switch to replacement mode to preview transformed text, choose whether replacement applies once or to all matches, and enter a replacement template. The page also offers case-insensitive, multiline, dot-all, verbose, and ASCII options.
This is a browser-based approximation of common Python re patterns, not a Python interpreter or a full implementation of Python’s regular-expression engine. It adapts Python-style named-group syntax and removes whitespace and comments for verbose mode, then evaluates patterns with the browser’s JavaScript regular-expression engine. Engine differences mean a pattern can preview successfully here and still behave differently in your target Python version.
The match view reports every match found in the sample text and displays captured groups for each result. A group is the part of a match enclosed in parentheses; a named group gives that part a label. In replacement mode, the replacement field is applied to the first match or all matches according to the replace-all checkbox. The result is a preview only, not an edit to a file or a running Python program.
The available flags cover common tasks: ignore case, treat line boundaries as multiline anchors, let a dot match line breaks, ignore whitespace/comments in verbose patterns, and restrict shorthand classes to ASCII behavior. Some Python options and syntax are not supported, and similarly named flags can differ between engines.
Guide
Follow the workflow and verify inputs and outputs with practical examples.
Enter the pattern and paste or type sample text. Both are needed to show matches. Use the example control if you want a starting pattern with a named group.
Turn on only the options relevant to the Python pattern you are approximating. Review the active flags and whether the pattern was adapted for display.
Inspect the highlighted spans, match count, and captured group values. A zero count means the current pattern did not match the supplied sample.
For a substitution, switch to replacement mode, type a replacement template, and choose first-only or replace-all behavior. Read the entire replacement preview before copying it.
Run the final pattern and replacement in the exact Python version and application where they will be used, especially before relying on edge cases or Unicode behavior.
Use cases
See how the tool fits into real work and everyday tasks.
A learner can try a pattern against a short sample and inspect where it matches and what each capture group contains before writing Python code.
An editor or developer can preview a replacement against representative text, check the match count, and compare one-match with replace-all output.
A teammate can prepare a small pattern-and-text example to discuss expected matches. Treat the preview as a debugging aid and verify behavior in the actual runtime.
Q&A
Find concise answers to common questions and confusing cases.
No. It uses the browser’s JavaScript regular-expression engine with selected syntax adaptations. It does not execute Python code or promise full compatibility with Python’s re module.
Python and JavaScript regex engines do not support exactly the same syntax or semantics. Simplify the pattern to common constructs, inspect the displayed error, and test it in the target Python version before relying on the result.
Check that the pattern matches the text, that replacement mode is selected, and that the replacement field is not empty. A zero match count means there is nothing to replace.
The ASCII option changes some character-class behavior, and Unicode handling can differ from Python. Use representative non-sensitive sample text, then verify important cases in the target environment.
Notes
Review scope, result limitations, and important precautions before use.
A successful preview does not prove that a pattern is correct, complete, or compatible with every Python version. Confirm syntax, flags, capture behavior, replacement references, and Unicode cases in the intended Python runtime. Test against realistic edge cases and validate any data-processing result before using it operationally.
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