The AI Regex Prompt Builder lets you describe what you want to match in plain English and generates a highly optimized prompt for AI assistants like ChatGPT, Claude, or Gemini to produce the perfect regular expression. No more struggling with cryptic regex syntax — just describe your intent and let AI handle the pattern.
Step-by-Step
Describe your pattern — Type in plain English what you want to match (e.g., "email addresses ending in .edu" or "phone numbers in US format with optional country code").
Add test strings — Optionally provide example strings that should match and strings that should NOT match so the AI can validate its output.
Select the regex flavor — Choose from JavaScript, Python, PCRE, Go, Java, or .NET regex flavors since they have subtle syntax differences.
Review the generated prompt — The tool creates an optimized AI prompt that includes your description, test cases, desired flavor, and instructions for the AI to explain each part of the regex.
Copy and paste — Send the prompt to your preferred AI assistant and receive a well-explained, tested regex pattern.
Features
Plain English Input — Describe your matching requirements in natural language. No need to know regex syntax beforehand.
Optimized AI Prompts — Generates prompts that include best-practice instructions for AI regex generation: "provide the regex, explain each capture group, include edge cases, show test results."
Test Case Builder — Add positive and negative test cases that are included in the prompt so the AI can self-verify the regex it generates.
Common Pattern Library — Browse pre-built descriptions for common patterns (emails, URLs, IP addresses, dates, phone numbers, credit cards, hex colors) and customize them for your needs.
Multi-Flavor Support — Generates flavor-specific prompts since regex features like lookbehind, named groups, and Unicode properties vary between JavaScript, Python, PCRE, and other engines.
Prompt History — Keeps a local history of your regex descriptions so you can revisit and refine previous prompts.
Common Use Cases
Form Validation — Generate regex patterns for validating emails, phone numbers, postal codes, and custom input formats.
Log Parsing — Describe log line formats in English and get regex patterns to extract timestamps, error codes, and messages.
Data Extraction — Build patterns to pull structured data from unstructured text like scraping HTML, parsing CSVs, or mining documents.
Code Refactoring — Generate find-and-replace regex patterns for IDEs to rename variables, update import paths, or restructure code.
Security — Create patterns to detect potentially malicious input, SQL injection attempts, or XSS payloads.
Why Use This Tool
Regular expressions are one of the most powerful tools in programming, but their syntax is notoriously hard to read and write. Most developers either copy patterns from Stack Overflow without understanding them or spend excessive time debugging character classes and quantifiers. This tool bridges the gap by translating your intent into a precise AI prompt that consistently produces correct, well-documented regex patterns. The included test cases and flavor targeting eliminate the most common regex pitfalls.