Regex generation from examples
Data as of Oct 25, 2026
Reviewed by Dimitry Apollonsky
Which brands AI mentions
Mentioned in · Sep 29 – Oct 25, 2026
ChatGPT SearchChatGPT SearchGoogle AI ModeGoogle AI Mode
- =1OpenAIChatGPT Search 25%Google AI Mode 36%
- =1Regex101ChatGPT Search 25%Google AI Mode 36%
- =1Regex GeneratorChatGPT Search 17%Google AI Mode 36%
- =1RegExrChatGPT Search 0%Google AI Mode 55%
- =1SimplicalcsChatGPT Search 42%Google AI Mode 0%
Questions and answers
Google AI ModeOct 25, 2026
The exact tool you are looking for—where you paste sample text and visually highlight or select specific segments to generate the corresponding pattern—is the Regex Generator by Olaf Neumann.
Why the Regex Generator fits:
- Visual Selection: You paste your text block and click/highlight the exact parts you want your expression to match.
- Real-Time Generation: It automatically builds and updates the regular expression pattern live as you change selections.
- Multi-Language Export: It instantly outputs code snippets for various programming languages (Python, JavaScript, Java, C#, Go, Ruby, Swift, and more).
Alternative Approaches
If you want to try other interactive approaches to regex building:
- AI-Powered Generators: Tools like Rows Regex Generator let you describe what you want to extract in plain English rather than highlighting.
- Inspect & Explain Tools: RegExr works in reverse—you paste a regex and highlight elements of the expression to see what they mean breakdown-style.
Would you like help writing a specific regex pattern manually , or do you want to share a sample of the text you are trying to parse?
ChatGPT SearchOct 25, 2026
Yes — there are a few tools that do exactly this: paste a block of text, highlight the parts you want to match, and automatically generate a regular expression (regex). I'd start with these three.
My top recommendations
1. Regex Painter
(Best for your exact use case)
Website:
Paste sample lines, highlight the text you want to match, and watch the regex appear automatically. You can highlight multiple examples to help the tool infer a more general pattern, then copy the result. It runs in your browser. unfckr.appregex-builder.com Best for: extracting IDs, dates, values, and other structured text from logs or documents.
2. Regex Builder
Website:
Highlight variable sections in an example sentence to create named capture groups. You can tune each group's pattern, test it against text, and export code for JavaScript, Python, Go, Java, C#, PHP, Ruby, and Rust. It also processes text locally in your browser. regex-builder.comunfckr.app Best for: extracting several fields from a text block into separate named variables.
3. Simplicalcs Regex Tester
Website:
Highlight part of your sample text to build a matching pattern, or use its Guess pattern feature. It also provides live match highlighting, replacement mode, and a plain-English explanation of the regex. simplicalcs.com Best for: quickly generating and testing a regex without setting up capture groups manually.
Which one should you choose?
If you want to… Choose Highlight text and automatically infer a matching regex Regex Painter Extract multiple fields from one text block Regex Builder Generate a pattern and immediately test it Simplicalcs My recommendation: Try Regex Painter first. Its workflow most closely matches what you described, including highlighting multiple examples to refine the generated pattern.
One important distinction: generating a regex from a single highlighted example can be ambiguous. For instance, highlighting
INV-0042could produce a pattern for that exact string or a reusable pattern for invoice IDs. Providing two or three examples helps clarify which behavior you want.One question: Are you looking to highlight one section of text to match repeatedly (such as all invoice numbers), or several different sections (such as a date, username, and error message) and generate one regex with capture groups? That would help me narrow this down to the best fit.
Sources cited in this answer6
- unfckr.appRegex Painter - highlight examples, get the regex · Unfckr
- unfckr.appRegex Painter - highlight examples, get the regex · Unfckr
- regex-builder.comRegex Builder — Build a regex from an example, no syntax needed
- regex-builder.comRegex Builder — Build a regex from an example, no syntax needed
- simplicalcs.comRegex tester — test regular expressions live | Simplicalcs
- simplicalcs.comRegex tester — test regular expressions live | Simplicalcs
ChatGPT SearchOct 23, 2026
For your specific requirement — generating a correct, efficient regular expression from example strings — I’d recommend Regex.ai as the first tool to try, or ChatGPT for more complex patterns where correctness, edge cases, and performance matter.
My top recommendations
1. Regex.ai — best for learning from examples
Paste sample text, highlight the portions you want to match, and compare candidate regex patterns. Its example-driven workflow makes it a particularly good fit when you already have real strings rather than a written specification.
Website:
2. ChatGPT — best for complex logic and optimization
Supply examples that must match and examples that must fail. I can infer the intended structure, explain the expression, target your particular regex engine, and help test edge cases and potential performance problems.
Website:
3. RegexKit — best for generation plus testing
Generates a pattern with an explanation and test cases, with support for JavaScript, Python, PCRE, Go (RE2), and Java. It also lets you supply example text.
Website:
4. regex101 — best for verification
Pair it with an AI generator to test matches, inspect capture groups, and debug the result. It's a testing companion rather than my first choice for inferring an entire complex pattern from examples.
Website:
How to get the most accurate result
The important distinction is that matching your examples is not the same as inferring the correct general rule. Many different regexes can match the same sample strings.
For the best result, provide:
- Positive examples: strings that must match.
- Negative examples: strings that must not match.
- Regex flavor: for example, .NET, PCRE2, Python, JavaScript, or Java.
- Performance requirements: whether the pattern must avoid catastrophic backtracking on long or malformed input.
You can use this prompt with ChatGPT or another coding AI:
:::writing{variant="document" id="58314"} Generate an accurate, efficient regular expression from the examples below.
Regex engine: [Specify language and engine]
Must match:
- [Example 1]
- [Example 2]
- [Example 3]
Must not match:
- [Counterexample 1]
- [Counterexample 2]
Requirements:
- Infer the underlying structure, not just the literal examples.
- Match the entire string unless specified otherwise.
- Prefer a readable, maintainable expression.
- Avoid catastrophic backtracking and unnecessary complexity.
- Explain the regex and any engine-specific features.
- Test every supplied example and report the results.
- Identify ambiguous requirements and suggest additional edge cases.
Return the regex, an explanation, and a small test suite. Do not claim correctness beyond the cases and rules actually verified. :::
My recommendation: Start with Regex.ai if you want a dedicated example-driven tool. Use ChatGPT if the pattern has nested conditions, optional sections, lookarounds, or strict performance requirements. Validate the final result with a real test suite before deploying it.
If you want, you can also paste your actual example strings here — including a few that should not match — and tell me which programming language or regex engine you're using. I can work out the pattern and help verify its correctness and efficiency.
Sources cited in this answer6
- toolypedia.comRegex.ai: Uses & Key Features
- regex.aiRegex.ai - Artificial Intelligence Regular Expression Generator
- chatgpt.comChatGPT: Chat, Work, Create & Code with AI
- regexkit.devRegex Generator — Describe It in English, Get a Tested Pattern | RegexKit
- regexkit.devRegex Generator — Describe It in English, Get a Tested Pattern | RegexKit
- regex101.comregex101: Online Regex Tester, Builder & Debugger
Google AI ModeOct 23, 2026
When you want to generate a regular expression specifically from a set of example strings (rather than just typing a text prompt), specialized visual AI tools and large language models handle the job differently.
Top choices specifically designed or exceptionally good at building regex from examples include:
- Regex.ai — A dedicated AI-powered tool built precisely for this workflow. You paste your target text and highlight/select the exact examples of what you want to match. The AI analyzes your selections and outputs the matching regular expression on the fly.
- General LLMs (ChatGPT, Claude, or Gemini) — While they use text prompts instead of a visual highlighter, modern LLMs are remarkably strong at regex if you supply a clear list of "should match" and "should not match" examples. Claude (Anthropic) and GPT-4o tend to excel here because you can converse with them, paste 10–20 varied examples, and ask them to refine the expression when an edge case fails.
- Workik AI Regex Generator — Another utility tool that lets you feed input examples or descriptions to generate and test code snippets across different regex engines (like PCRE, Python, or JavaScript).
Tips for Best Results with Examples
No matter which AI you use, complex patterns require good data hygiene. When you prompt the AI, structure your input like this:
"Generate a regular expression that matches the following valid examples:
[EXAMPLE 1][EXAMPLE 2]
But it must NOT match these invalid examples:
[COUNTER-EXAMPLE 1][COUNTER-EXAMPLE 2]
Target language/engine: Python / JavaScript / etc."
If you want, you can share a few of your example strings and what you're trying to extract right here, and I can write and test the regex pattern for you.
Also asked as
- Can you create a regular expression that matches every string in this list I have?
