How do named groups work in this tester?

You can use either standard .NET named capture syntax: (? ...) or (?'name'...). Captured values are displayed in a structured table and reflected in the generated C# snippet via match.Groups["name"].

What replacement syntax is supported?

The tester supports .NET-style replacement placeholders, including named placeholders like ${name} and numeric capture groups like $1 or ${1}.

Are character classes like \d, \w, and \s Unicode-aware?

Yes. By default, Unicode character class handling is enabled to match .NET behavior, but you can disable the toggle to restrict them to ASCII ranges.

Are balancing groups and class subtractions supported?

Advanced .NET features like balancing groups (? ...) and class subtractions [a-z-[aeiou]] are detected and reported with an explanatory notice rather than silently failing.

Does this tool generate C# code automatically?

Yes. It creates a ready-to-paste C# snippet using System.Text.RegularExpressions.Regex configured with your chosen RegexOptions and group lookups.

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C# Regex Tester (.NET)

Test .NET/C# regular expressions online with named groups ((?<name>…)), IgnoreCase/Multiline/Singleline options, match highlighting, capture-group tables, a ready-to-paste C# snippet and an IgnorePatternWhitespace preview.

Details

What this tool helps you do

A regex tester tuned to the .NET flavor used by C# and System.Text.RegularExpressions. Type the pattern exactly as you would in C# — named groups (?…) or (?'year'…), backreference \k, RegexOptions flags — and the tester translates it to the platform's ECMAScript engine, runs it against your test string, and reports every match, every capture group (with names), and a replace preview using ${name} / $1 substitution syntax. It also prints ready-to-paste C# code with the right RegexOptions and match.Groups["name"] access. The report shows the translated pattern so you can see exactly what ran. .NET-specific facts are baked in: \d \w \s are Unicode by default (toggleable), lookbehind may be variable length, and balancing groups (?…) plus [a-z-[aeiou]] class subtraction are detected and rejected with an explanation instead of mismatching silently. Note that .NET numbers unnamed groups before named ones — a quirk this emulator (like most engines) does not reproduce, so prefer named groups when order matters.

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Pattern: (?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2}) Subject: deployed 2026-09-01, rollback window 2026-09-03 Flags: Global: true, IgnoreCase: false, Multiline: false, Singleline: false, Unicode: true

C# Regex Tester (.NET)

What this tool helps you do

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Examples that match this tool

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Extracting ISO Dates with Named Groups

2. Matching and Replacing HTML Tags Case-Insensitively

FAQ

Regex Named Capture Groups

Regex Replace Samples

Common Regex Patterns

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