Are regular expressions evaluated locally without transmitting data to a server?

Yes, 100%. All pattern compilation, regex execution, and string transformations run purely in your local browser sandbox. No sensitive test payloads, logs, or proprietary tokens ever leave your device.

Which regular expression dialect is used by this tester?

The tester uses ECMAScript / JavaScript regular expression syntax (compliant with ES2024+ specifications), which supports named capture groups, Unicode property escapes, lookbehind assertions, and standard regex flags.

How does the substitution and replacement feature work?

In the Substitute tab, enter your replacement pattern. You can reference entire matches with $&, numbered capture groups with $1, $2, or named capture groups with $ .

What is the maximum test string size supported?

Because evaluation occurs directly in your local hardware memory, you can safely test large strings up to several megabytes with sub-millisecond execution times.

What are the most common regex flags and what do they do?

The "g" flag enables global searching across the entire string rather than stopping at the first match; "i" ignores case differences; "m" causes ^ and $ to match the beginning and end of each line; and "s" (dotAll) allows the dot (.) token to match newline characters.

正则表达式测试与可视化工具

API 即将上线

实时测试、调试与可视化正则表达式。纯前端零知识评估，支持捕获分组与常用模式预设。

Regex Tester & Real-Time Visualizer

Quick Regex Presets

Regular Expression

Flags:

//g

Test String115 chars

Highlighted Matches

Contact support@x114.org or dev.team+filter@cloud-service.io for inquiries. Invalid: test@, @example.com, user@.com

Detailed Captures (2)

Match #1Index: 8..24 (16 chars)

support@x114.org

Match #2Index: 28..60 (32 chars)

dev.team+filter@cloud-service.io

100% In-Browser Evaluation: Your regex expressions and test data never leave your local browser RAM. No servers or third-party APIs are contacted.

API 版本即将上线

Regex Tester & Visualizer API 上线时通知你。

关于

Regular expressions (Regex) provide a powerful, standardized DSL (Domain-Specific Language) for pattern matching, data extraction, string validation, and lexical parsing across modern software stacks. Whether you are validating RFC 5322 email addresses, parsing ISO 8601 timestamps, extracting URL query parameters, or sanitizing user inputs in backend controllers, regular expressions are an indispensable tool for every software engineer.

However, writing and debugging complex regular expressions with nested capture groups, negative lookaheads, and optional flags is notoriously error-prone. Even a single misplaced delimiter or catastrophic backtracking quantifier can cause subtle production bugs or ReDoS (Regular Expression Denial of Service) vulnerabilities.

Our Regex Tester & Visualizer delivers an instant, zero-knowledge development environment directly in your browser. Every character evaluation, capture group decomposition, and match highlight runs 100% locally in your client's JavaScript engine without transmitting test strings, confidential credentials, or customer PII across the network.

Key Architectural Capabilities

Real-Time Visual Highlighting: Alternating high-contrast visual badges highlight matches and boundary coordinates as you type.
Capture Group Decomposition: Automatically inspects named groups (?<name>) and numbered sub-patterns with starting/ending character indices.
Full Flag Matrix Support: Easily toggle g (Global), i (Case-Insensitive), m (Multiline), s (DotAll), and u (Unicode) modifiers.
Substitution & Replacement Preview: Test replacement patterns using native tokens like $1, $2, and $& with instant live output.
Code Snippet Generator: Export ready-to-run code snippets in JavaScript/TypeScript, Python (re), Go (regexp), and Rust (regex).
Comprehensive Cheat Sheet Presets: Includes battle-tested patterns for emails, IPv4 addresses, ISO dates, JWT structures, URLs, and hex colors.