Plain find and replace only works when you already know the exact text you want to change. Real cleanup jobs are messier: dates in several formats, numbers buried in sentences, inconsistent spacing, or tags that vary from line to line. Regular expressions describe the shape of the text you want, so one pattern can match thousands of variations at once. This tool applies a regex pattern across pasted text, shows how many matches it found, and replaces each one using your replacement string, including capture group references such as the first group. It is ideal for reformatting logs, normalising data exports, and cleaning text before it goes into a document or a database.
Quick Answer: Paste your text, type a regex pattern and a replacement, then click Replace All. The match count and the transformed text appear immediately.
Free Online Tool
Regex Find & Replace Tool
Replace text by pattern, with capture groups and a match count.
How to Use the Regex Find & Replace Tool
- Paste the text you want to change into the main input box.
- Type your regular expression pattern, for example a pattern that matches one or more digits.
- Type the replacement text, using group references such as the first capture group where needed.
- Set the flags you need, such as global replacement or case insensitive matching.
- Click Replace All and review the match count and the transformed output before copying it.
Key Features
- Full regex support using the browser’s own regular expression engine, including character classes and quantifiers.
- Capture group references in replacements, so matched parts can be reordered or wrapped in new text.
- Match counting, so you can see exactly how many replacements were made before trusting the result.
- Flag control for global, case insensitive and multiline matching from a single flags field.
- Clear error messages when a pattern is invalid, naming the problem instead of failing silently.
Best Practices and Tips
- Test a pattern on a small sample first. A greedy quantifier can swallow far more text than you intended on a long document.
- Use a capture group when you need to keep part of the match, such as keeping the digits while changing the punctuation around them.
- Escape special characters such as dots and brackets when you mean them literally, otherwise they act as pattern operators.
- Prefer the global flag for cleanup jobs, but run without it first if you only want to change the first occurrence.
Common Mistakes to Avoid
- Forgetting the global flag and wondering why only the first match changed while the rest stayed untouched.
- Writing a pattern that matches empty strings, which can insert replacements in surprising places throughout the text.
- Using a replacement group reference that does not exist, which silently inserts an empty string in its place.
Frequently Asked Questions
How is this different from plain find and replace?
Plain find and replace matches one exact string. A regex pattern matches a whole family of strings that share a shape, such as any number, any email like token, or any date. That makes it the right tool for reformatting inconsistent data where the exact values differ from line to line.
What are capture groups?
Parentheses in a pattern mark a capture group, and the text matched by each group can be reused in the replacement. The first group is referenced as the first group token, the second as the second group token, and so on. This lets you rearrange matched text, for example swapping a day and month, without retyping the values.
Why did my pattern produce an error?
The most common causes are unbalanced parentheses, an unclosed character class, or a quantifier with nothing before it. The error message names the problem, and fixing the flagged character usually resolves the pattern immediately.
Is my text uploaded anywhere?
No. Matching and replacement run entirely in your browser with the built in regex engine. Pasted logs, data and drafts never leave your device.