Regex Line Filter

Filter multiline text line by line with a JavaScript regex and choose whether to keep matching or non-matching lines.

Pattern

Flags

Keep

Input lines

Filtered lines

ReadyThe regex is tested independently against each line.

Before reusing a regular expression

keeps the established regex widgets and worker-guarded execution paths intact while connecting testing, explanation, extraction, replacement, test cases, static risk review, and code generation. Pattern data stays in the browser, and the shared inspector can save an explicit pattern locally.

Regex flavor and performance boundaries

Interactive checks follow the JavaScript RegExp implementation available in the current browser unless a tool explicitly says otherwise. Token explanations and backtracking warnings are bounded static guidance, not PCRE/Python/.NET compatibility, formal complexity analysis, or proof that a pattern is safe for every possible input.