Regex Generator
Generate, test, and understand regular expressions instantly with our free online Regex Generator. Build complex regex patterns using natural language or simple visual controls. 100% client-side and privacy-friendly.
What Is This Tool
Regular expressions are powerful but notoriously difficult to write correctly by hand — a single misplaced character can cause unexpected matches or break validation entirely. This visual regex builder lets you construct accurate, production-ready patterns using a simple rule-based interface, no memorization of cryptic syntax required.
Select from presets like Email, US Phone, or ZIP Code to get started instantly, or stack custom rules to build patterns for your specific use case. Every pattern compiles in real time and is immediately testable in the live sandbox. Code snippets for JavaScript, PHP, Python, Java, and Go are generated automatically, ready to paste directly into your project.
How to Use
- Pick a preset or start fresh. Click any Quick Preset button — Email, URL, US Phone, ZIP Code, and more — to load a ready-made pattern instantly. Or click "Add Rule" to build from scratch.
- Configure each rule row. Choose from rule types like "Starts with", "Exact text", "Digits only", "Letters only", or "Length range", then enter the values that define your match.
- Tune regex flags. Toggle the global (g), case-insensitive (i), and multiline (m) flags in the Generated Regex section to control how matches are applied.
- Test against real data. Paste sample strings into the Test Input box. Matches are highlighted in the results pane as you type, with exact index positions shown below.
- Copy your code snippet. Switch between JavaScript, PHP, Python, Java, and Go tabs to get a language-ready code block. Click "Copy Code" to grab it.
- Review the Pattern Breakdown. Each token in your regex is explained in plain English at the bottom — helpful for catching greedy matches or unintended captures before you ship.
Key Features
- 12 built-in presets covering the most common US validation patterns: email, URL, phone (NXX-NXX-XXXX), date, password, username, IPv4, hex color, integer, ZIP code, SSN, and credit card.
- Five language outputs — JavaScript, PHP (PCRE), Python, Java, and Go — each correctly formatted with proper escaping and flag handling for that runtime.
- Live match highlighting shows exactly which substrings your pattern captures, with character-index positions displayed per match so you can verify precision.
- Plain-English pattern breakdown translates every regex token into a readable description, making it easy to confirm behavior and catch unintended wildcards.
- 100% client-side processing — your test strings, patterns, and data never leave your browser. No server calls, no logging, no accounts required.
Common Use Cases
- Form validation — enforce correct formats for email addresses, US phone numbers, ZIP codes, and passwords on registration and checkout forms.
- Data cleaning pipelines — identify and extract malformed entries, duplicate values, or inconsistent formatting in CSV exports and database dumps before import.
- Log parsing — pull out transaction IDs, error codes, timestamps, or IP addresses from raw server or application logs.
- API input sanitization — build patterns to validate path parameters, query strings, and JSON field values at the route or middleware layer.
- Content moderation — create filters to flag specific terms, patterns, or character sequences in user-submitted content before it reaches a database.
Frequently Asked Questions
Is my test data sent to any server?
No. Everything runs entirely in your browser. Your patterns, test strings, and any data you paste into the sandbox never leave your machine. There are no analytics on your inputs and no server-side processing of any kind.
Why are there separate code tabs for each language?
Regex syntax differs between languages — PHP uses PCRE delimiters, Python requires the re module, Go uses the regexp package, and Java uses java.util.regex. Each tab produces a properly formatted, copy-paste-ready snippet for that specific runtime so you don't have to adapt it manually.
How does the Length Range rule work?
The Length Range rule generates a .{min,max} quantifier, which matches any character (except newline) between the specified minimum and maximum count. This is useful for fields with fixed or bounded lengths, like ZIP codes (5 digits) or passwords (8–16 characters).
Can I use this to parse HTML or nested structures?
Regular expressions are not well-suited for recursive or deeply nested structures like HTML trees. This tool works best for predictable, flat patterns — form fields, tokens, log entries, and structured strings. For HTML parsing, a dedicated parser like Cheerio (JS) or BeautifulSoup (Python) is a better fit.
Why does the Pattern Breakdown show multiple cards?
Each card corresponds to one rule row in your builder. The breakdown maps every rule to its generated regex token and explains what it matches in plain English. This makes it easy to audit complex patterns piece by piece before using them in production.
What do the global, case-insensitive, and multiline flags do?
The global (g) flag finds all matches in a string, not just the first one. The case-insensitive (i) flag makes the pattern match regardless of letter case. The multiline (m) flag changes ^ and $ anchors to match the start and end of each line rather than the entire string.
Advanced Tips
- Always anchor your patterns. Adding a "Starts with" rule (^) and "Ends with" rule ($) prevents partial matches — for example, ensuring
abc@example.com_extradoesn't pass an email check. - Test both valid and invalid inputs. Paste examples that should match alongside ones that should not. If the pattern highlights something it shouldn't, a rule is too broad.
- Use Length Range for fixed-width fields. For ZIP codes, SSNs, or date segments, setting min and max to the same value (e.g., 5 to 5) enforces exact length.
- Check the Pattern Breakdown before deploying. Greedy matches from the Length Range rule (
.{n,m}) can capture unexpected characters. Review each token description to confirm the pattern matches only what you intend. - Toggle case-insensitive (i) for user-facing forms. Users enter data inconsistently — enabling this flag prevents false failures on fields where case doesn't matter, like usernames or hex colors.