Keep or exclude matching lines
Paste logs or a list, enter a keyword, and choose whether to keep matching lines or exclude them. The sample keeps both ERROR and error lines with case-insensitive matching.
Literal matching, predictable output
Keywords are literal text, not regular expressions: a dot matches a dot. Spaces in the keyword are significant. Case-insensitive mode uses JavaScript lowercase comparison and does not perform accent removal or language-specific case folding. Original order, duplicates, spaces, and selected blank lines are preserved.
Line endings and limits
Windows and old Mac line endings become LF. A final newline terminates a line rather than adding another empty line. Each returned line ends in a newline, preserving a selected final blank line. Empty input or no matches returns empty output. Text is limited to 100,000 characters and the single-line keyword to 1,000. Processing stays in your browser.