Build, test, and understand regular expressions with plain-English explanations for any pattern matching need.
Copy & paste the prompt below into your preferred LLM. Unless a specific AI model is mentioned, you can use whichever you prefer.
You are a regex expert. Help me build a regular expression pattern. What I need to match: - Description: [DESCRIBE IN PLAIN ENGLISH WHAT YOU WANT TO MATCH] - Example inputs that SHOULD match: [LIST 3-5 EXAMPLES] - Example inputs that should NOT match: [LIST 3-5 EXAMPLES] - Language/tool: [JAVASCRIPT / PYTHON / JAVA / PHP / GREP / OTHER] - Flavor: [PCRE / POSIX / ECMAScript / RE2 / OTHER / NOT SURE] Deliver: 1. **The Regex Pattern** — clean and optimized 2. **Character-by-Character Breakdown:** Explain every single character and group in the pattern 3. **Visual Diagram:** ASCII representation of how the pattern matches 4. **Test Results:** Show the pattern matching against all my example inputs with highlighted matches 5. **Edge Cases:** 5 tricky inputs that might break the pattern, and whether they match or not 6. **Variations:** - Strict version (exact matches only) - Lenient version (allows minor variations) - Named capture groups version (for extracting data) 7. **Code Snippet:** Ready-to-use code in my language showing the regex in action (match, find all, replace, validate) 8. **Common Mistakes:** What could go wrong with this pattern and how to avoid it 9. **Performance Note:** Is this pattern at risk of catastrophic backtracking? If so, how to fix it. No regex is self-documenting. Always explain what it does.
The reason "Regex Pattern Builder" outperforms a generic request is structural: it uses structured enumeration and reasoning elicitation and role assignment to constrain the AI's response toward production-quality code that handles edge cases and follows your stack conventions. What you get back is production-quality code that handles edge cases and follows your stack conventions - production-ready rather than a rough draft that needs heavy reworking.
These coding tips will help you get stronger results when using "Regex Pattern Builder" and similar prompts in this category.
"Regex Pattern Builder" is particularly useful in these situations. If any of these scenarios sound familiar, this prompt will save you significant time.
When you use "Regex Pattern Builder" with ChatGPT, Claude, or Gemini, here is what to expect in the AI output.
Adapt "Regex Pattern Builder" to your specific situation by modifying these key areas. The more context you add, the better the results.