Free AI Regex Generator & Builder (Online)

Type what you want to match in plain English, click Generate, and you get back a regular expression. That’s the whole tool. No account needed for your first few runs.

It returns only the pattern, not an explanation. So the better your description, the better the regex. Most of this page is about how to write that description so the pattern works on your real data the first time.

How to Use the Regex Builder

Describe what you want to match in the box above, like “a US phone number” or “everything inside square brackets.”
Add the language you’re using and two or three real examples (see the tips below).
Click Generate and copy the pattern.
Test it against your actual data before you use it. A free tester like regex101 shows exactly what each part matches.

How to Describe Your Pattern

A vague request gets a generic pattern. Compare “phone number” with “US phone numbers like (555) 123-4567 or 555.123.4567, but not numbers with a +1 country code.” The second one tells the generator which formats to accept and which to reject, and that’s where most patterns go wrong.

A few things that make a big difference:

Name your language or tool. JavaScript, Python, Go, a Google Sheets formula, and VS Code’s find-and-replace all read regex a little differently.
Paste real examples, including one that should not match. A pattern built from a single example usually breaks on the second one.
Say whether it’s for checking or finding. Validating a whole form field (the entire value must match) needs a different pattern than finding matches inside a paragraph.
When you’re pulling something out of text, describe what’s around it. “The number after the word Total” or “everything between SKU: and the next comma” gives the pattern something to hold on to.

Example Patterns

Here’s the kind of description that works, and a pattern like the one you’d get back:

“Email address”: [A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}. Good for everyday addresses. The fully spec-compliant version is hundreds of characters long, and you almost never need it.
“US phone number”: $?\d{3}$?[-.\s]?\d{3}[-.\s]?\d{4}. Covers the formats people actually type.
“Password with 8 to 16 characters, at least one lowercase letter, one uppercase letter, one number, and one symbol”: ^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[^A-Za-z0-9]).{8,16}$. Each (?=...) checks one rule.
“Date in YYYY-MM-DD format”: \d{4}-\d{2}-\d{2}. This checks the shape, not whether the date exists. Let your date library catch February 30.
“Hex color code”: #(?:[0-9a-fA-F]{3}){1,2}\b. Matches both #fff and #ffffff.
“The text inside each H2 tag”: <h2>(.*?)</h2>. The ? after .* keeps it from running all the way to the last closing tag on the page.
“The number after Total:”: Total:\s*(\d+(?:\.\d+)?). The part in parentheses is the number you’re after.

Regex Flavors: Why a Pattern Works in One Language and Not Another

Most regex syntax is shared, but a pattern copied from one language can fail in another. The differences that trip people up most:

Python writes named groups as (?P<name>...), while JavaScript uses (?<name>...). Copy one into the other and it won’t compile.
JavaScript supports lookbehind in current browsers, but Safari only added it in version 16.4. If your code has to run on older iPhones, avoid it.
Go (and Google Sheets) use the RE2 engine, which has no lookarounds or backreferences. The password pattern above won’t run there, so you’d check each rule with its own simple pattern instead.
Java needs every backslash doubled inside a normal string, so \d becomes \\d in your code.
.NET (C#) has the most features of the group, including lookbehind of any length.

Common Regex Mistakes

Matching too much. .* grabs as much as it can. Use .*? when you want the shortest match.
Forgetting to escape. A plain . matches any character, so example.com also matches “exampleXcom”. Write example\.com.
Leaving out anchors. Without ^ at the start and $ at the end, a validation pattern passes any value that merely contains a match.
Nested repeats like (a+)+. On some inputs these take so long they freeze your app. Keep patterns that run on user input simple.
Parsing HTML with regex. Fine for a quick scrape of predictable markup. For anything else, use an HTML parser.

Test It Before You Use It

A generated pattern is a starting point. Paste it into a tester with your real data, then try the cases most likely to break it: an empty value, extra spaces, an international phone number, a name with an apostrophe. If something fails, add that example to your description and generate again.

Regex Generator FAQs

Is the regex generator free?

Yes. You can run it a few times without an account, and a free RightBlogger account keeps it going.

Do I need to know regex to use it?

No. You describe the match in plain English. Knowing a little helps you check the result, and comparing your description to the pattern you get back is a decent way to learn the syntax.

Does it explain the pattern?

No, it returns only the regex. To see what each part does, paste the pattern into regex101, which breaks it down piece by piece.

Does it work for JavaScript, Python, PHP, and other languages?

Yes, as long as you name the language in your description. The core syntax is the same everywhere, and the generator can account for differences like Python’s named groups or Go’s missing lookarounds when it knows what you’re using.

Will the pattern always be right?

Not always. It handles common requests well, but regex is full of edge cases. Test the output on real data, especially for form validation, where a missed case lets bad input through.

What does RightBlogger cost beyond the free tools?

Paid plans start at $49/month billed annually ($59 month to month) for Solo, with unlimited AI words across every tool. Pro is $69/month billed annually for 3 sites and 3 seats, and Agency is $199/month billed annually for 10 sites and 5 seats. Every paid plan starts with a 7-day free trial and a 30-day money-back guarantee. See pricing for details.