Regex from Examples
Paste a few example strings that should match and a few that shouldn't — the tool generates a regex pattern that handles both, plus a one-line plain-English explanation of what it matches. Works for emails, phone numbers, log line patterns, URL shapes, IDs, or any custom string format. AI-powered.
Tips for better results
- • Give at least 3-5 matching examples that vary
- • Include near-miss negatives (subtle differences)
- • One string per line, no commas or quotes
- • The more varied your matches, the tighter the regex
- • Test the output against your real data
- • Works for any engine (JS, Python, Go, PCRE)
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Frequently Asked Questions
- How many examples should I give?
- Aim for 3-5 positive examples that cover the variation you want to match, and 2-3 near-miss negatives. The more varied and realistic the examples, the tighter the generated regex. Too few examples produce overly loose patterns; too many similar examples waste tokens.
- What regex engines does the output work with?
- The tool generates POSIX/PCRE-compatible patterns that work in JavaScript, Python, Go, Ruby, and most modern regex engines. If you need a specific dialect (like Vim, .NET, or grep basic), you may need to tweak character classes or anchors.
- Will it always match my examples exactly?
- The prompt instructs the AI to mentally test the regex against every example before answering, but AI output is not guaranteed. Always verify the generated regex against your real data. For critical matching logic, use the regex as a first draft and test thoroughly.
- Why not just write the regex myself?
- If you already know regex well, you probably don't need this. But many developers recognize regex they didn't write faster than they write it from scratch. This tool compresses the think-and-test loop into a 3-second round trip.
- Is my input stored?
- The examples are sent to MarkdownMe's AI endpoint only to generate the regex. You choose whether we keep it to improve the tools. See the privacy page.
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About Regex from Examples
Give 3-5 strings that should match and 3 that shouldn't. AI generates a readable regex that fits. Free, no login. This AI-backed tool sends your input to MarkdownMe's capped AI endpoint to generate the result. You choose whether we keep it to improve the tools. See the privacy page. No account is required. MarkdownMe provides free, fast, and reliable Markdown tools for developers, writers, and anyone who works with Markdown.