Regex Cheatsheet
Regular expressions are powerful, terse, and easy to misuse. A good cheatsheet is most helpful when it gives practical patterns with context rather than pretending one expression can validate every real-world edge case. The CodeToolia Regex Cheatsheet provides copyable examples for email-like strings, URLs, IPv4 addresses, UUIDs, and simple JSON value extraction. Each pattern includes a short note explaining where it is useful and where it is limited. Use these expressions for prototypes, logs, tests, and small parsing tasks, but prefer proper parsers for complex formats and security-sensitive validation.
About Regex Cheatsheet
Copy practical regex examples for email, URLs, IPv4, UUIDs, and JSON-like extraction. This utility is part of CodeToolia, a collection of tools designed to simplify web development workflows. Like all our utilities, this tool operates entirely on the client side, meaning your data is processed locally within your browser and is never transmitted to any server.
Privacy & Security
We prioritize your privacy. By using browser-based technologies (Web APIs), we ensure that sensitive data—such as API keys, JSON payloads, or personal identifiers—stay strictly within your local environment.
How to use
- Choose a regex example from the list.
- Review the pattern and its intended use.
- Copy the expression and adapt it to your language or validation rules.
How this tool works
Regex Cheatsheet is designed around a simple rule: keep the transformation visible, reversible when possible, and easy to verify before the result leaves your browser. Many developer utilities look small because the interface is only an input and an output, but the value comes from reducing uncertainty in a frequent workflow. This tool gives you a focused place to inspect the data, run the operation, and compare the result without opening a large IDE, writing a one-off script, or sending the value to a remote API.
The implementation runs on the client side and is intentionally narrow. That matters for developer tools because developers often paste examples from logs, staging systems, documentation, browser consoles, or API clients. A local-first workflow lowers friction and keeps the page useful even for quick checks. It also makes the behavior easier to reason about: the input you see is the input being processed, and the output is produced immediately in the same session.
Common use cases
Use Regex Cheatsheet when you are debugging a request, preparing a code example, building a fixture, reviewing a copied value, or checking whether a teammate's sample behaves the way you expect. It is especially helpful during small interruptions in a normal development day, when switching context to a heavier tool would take longer than the actual operation.
The page is also useful as a teaching and documentation aid. You can paste a short sample, show the result, and then copy the output into an issue, pull request, test case, or internal note. Because the surrounding page includes examples, related tools, and FAQ entries, users who arrive from search can understand not only what the tool does, but also when the result should be trusted and when a more specialized workflow is appropriate.
Example
UUID v4 regex: /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/iAccuracy and privacy notes
Treat the output as a practical development aid rather than a substitute for production validation. Different platforms may apply slightly different rules, especially around encodings, browser APIs, timestamps, redirects, regular expressions, and security-sensitive data. For important production changes, verify the result in the same runtime, framework, or service that will consume it.
Avoid pasting private credentials, personal data, or production secrets into any online tool unless you fully control the environment. CodeToolia tools are built to process values locally in the browser, but careful data handling is still a good engineering habit. When sharing examples publicly, replace real identifiers and sensitive fields with safe sample values.
FAQ
Can regex fully validate email addresses?+
Not perfectly. Practical regex checks format, while real deliverability requires other checks.
Should I parse JSON with regex?+
Use JSON.parse for real JSON. The JSON example is only for simple log extraction.
Are patterns language-specific?+
The examples are JavaScript-style and may need small changes elsewhere.