Overview
Regex101 is a powerful online regular expression tester designed for developers, QA engineers, and data professionals who work with complex text patterns. Supporting multiple regex flavors such as PCRE, JavaScript, Python, and Golang, it lets you write, debug, and optimize expressions directly in your browser. As you type, Regex101 provides instant match highlighting, detailed token-by-token explanations, and real-time error feedback so you can understand exactly how your pattern behaves.
The tool includes an integrated regex debugger, allowing you to step through your pattern and visualize the matching engine’s process. A built-in reference sheet and quick syntax helper make it easy to learn or recall advanced constructs without leaving the page. You can save expressions to your account, create sharable links, and collaborate with teammates when troubleshooting tricky patterns.
Regex101 is ideal for tasks like validating user input, cleaning data, extracting structured information from logs, and building search or replace rules for applications. With features like test string management, substitution previews, and performance hints, it helps you write more reliable, efficient regular expressions faster. Whether you are just learning regex or you rely on it daily in production systems, Regex101 provides a convenient, developer-friendly environment that turns trial-and-error into a clear, guided workflow.
Pricing
Freemium
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Use Cases
- Design and validate complex form input rules for emails, passwords, or custom IDs before integrating them into your backend or frontend code.
- Extract structured fields such as timestamps, log levels, and user IDs from server logs or text files for monitoring and analytics pipelines.
- Prototype and refine search-and-replace rules to clean or reformat large text datasets, configuration files, or legacy codebases.
- Debug failing regex patterns from production systems by sharing test cases with teammates and stepping through the matching process.
- Learn and practice regular expressions interactively with instant feedback, examples, and detailed explanations of each pattern.
Features
Real-time regex evaluation
Multi-flavor regex support
Step-by-step regex debugger
Detailed token explanations
Instant error and warning hints
Search, replace, and preview
Sharable regex snippets
Built-in syntax reference
Reviews
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FAQ
Is Regex101 free to use?
Regex101 offers a fully functional free online regex tester. Some advanced or account-based features may require registration, and pricing or premium options can change over time, so check the official site for the latest details.
Which regex flavors does Regex101 support?
Regex101 supports multiple regular expression flavors, including PCRE, JavaScript, Python, and Golang. You can switch flavors in the interface to match the runtime you use in your application.
Can I save and share my regular expressions?
Yes. You can create an account to save your regular expressions, store test strings, and generate shareable links so others can view or debug the same pattern and inputs.
Is Regex101 suitable for beginners learning regex?
Regex101 is well suited for beginners because it shows detailed explanations for each token, highlights matches in real time, and includes built-in documentation, making it easier to understand how patterns work.
Can I use Regex101 for large-scale production data?
Regex101 is designed as a development and testing tool. You should prototype and validate your expressions there, then run them in your own production environment where you control data, performance, and security.