Regex Tester & Validator
Test, validate and match regular expressions
AI Regex Generator
Generate regular expressions from plain English. Describe what you want to match, and RegexTester.dev turns it into a tested regex — no regex syntax knowledge required.
Open the AI Regex TesterGenerate from text
Describe what you want to match in plain English and get a ready-to-use regex.
Explain any regex
Paste a pattern and get a plain-English summary plus a token-by-token breakdown.
Infer from samples
Highlight text you want to match and let the AI infer a general pattern.
Optimize & detect risk
Catch ReDoS and catastrophic backtracking, and get a cleaner pattern.
How it works
- 1
Describe in plain English
Type something like "match all email addresses" or "capture the date in YYYY-MM-DD format".
- 2
Generate & explain
The AI returns a regex with appropriate flags and a short explanation of what each part does.
- 3
Test instantly
One click applies the pattern to the tester, where matches highlight in real time across your test strings.
Example requests
The kinds of descriptions the AI handles well — try them in the generator.
“Match an email address and capture the local part and domain”
/^([A-Za-z0-9._%+-]+)@([A-Za-z0-9.-]+\.[A-Za-z]{2,})$/“Match US phone numbers in formats like (123) 456-7890 or 123-456-7890”
/\(?\d{3}\)?[-.\s]?\d{3}[-.\s]?\d{4}/g“Extract http and https URLs from text”
/https?:\/\/[\w\-.]+(:\d+)?(\/[\w\-./?%&=#]*)?/gi“Match dates in YYYY-MM-DD format”
/\d{4}-\d{2}-\d{2}/g“Require at least 8 chars with uppercase, lowercase, digit, and symbol”
/^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&]).{8,}$/“Match a valid IPv4 address”
/\b(?:\d{1,3}\.){3}\d{1,3}\b/gAI-assisted vs. writing regex by hand
Hand-writing regex is error-prone, especially for lookarounds, Unicode, and nested quantifiers. The AI handles the first draft, flags performance risks, and explains the result — while the integrated tester verifies exactly what matches. You stay in control; the AI removes the boilerplate and the guesswork.
Always verify AI-generated regex before using it in production. Regex behavior varies across engines, and the tester is the fastest way to confirm a pattern does exactly what you expect.
Frequently asked questions
How do I generate a regex with AI?
Describe what you want to match in plain English (for example, "match all email addresses and capture the domain"), then click Generate. The AI returns a ready-to-use regex with flags and a short explanation, which you can apply to the tester with one click.
Is the AI regex generator free?
Yes. The AI regex generator is completely free and requires no signup. To keep the service sustainable, each IP has a small daily request limit.
Which regex flavors does the AI support?
The AI generates patterns compatible with JavaScript, Python, PHP (PCRE), Java, Go, .NET, and Rust. The tester highlights matches using a WebAssembly engine that understands the differences between these flavors.
Can the AI explain an existing regex?
Yes. Paste your pattern and switch to the Explain tab to get a plain-English summary, a token-by-token breakdown, and practical tips about gotchas like greedy matching and backreferences.
Can the AI detect ReDoS or catastrophic backtracking?
Yes. The Optimize tab reviews your pattern for correctness, readability, and performance risks such as catastrophic backtracking (ReDoS), and suggests an improved version when one exists.
How accurate is AI-generated regex?
The AI is strong at common patterns, but regex behavior can vary across engines. Always review the generated pattern — the integrated tester shows you exactly what it matches in real time so you can verify before using it.