Regex Replace API - Free Find & Replace
Applies a regex pattern to a string and replaces all matches with the specified replacement. Supports backreferences ($1, $2) for capture groups in the replacement string.
Code examples
curl -X POST https://api.botoi.com/v1/regex/replace \
-H "Content-Type: application/json" \
-d '{"pattern":"(\\d{4})-(\\d{2})-(\\d{2})","flags":"g","testString":"Event date: 2026-03-26","replacement":"$2/$3/$1"}'When to use this API
Reformat dates across a document
Convert all ISO dates (YYYY-MM-DD) to US format (MM/DD/YYYY) or any other format using capture group backreferences.
Redact sensitive information in logs
Replace credit card numbers, SSNs, or API keys in log files with masked values like "****" before sharing.
Frequently asked questions
How do backreferences work in the replacement string?
Use $1 for the first capture group, $2 for the second, and so on. $0 refers to the entire match.
Does the replacement happen only once or globally?
It depends on whether you include the "g" flag. Without "g", only the first match is replaced. With "g", all matches are replaced.
Can I use lookahead and lookbehind in the pattern?
Yes. The regex engine supports lookahead (?=), negative lookahead (?!), lookbehind (?<=), and negative lookbehind (?<!).
Is there a ReDoS protection for replacement patterns?
Yes. The same 5-second execution timeout applies. Patterns that cause catastrophic backtracking are terminated.
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