Filter Lines by Rule
Filter text lines by pattern, length, or content. Keep or remove lines that match your criteria instantly.
About This Free Online Filter Lines by Rule
Our free online line filter tool lets you keep or remove lines based on custom rules. Filter by text pattern (substring or regex), by line length (minimum and/or maximum characters), or by content type (keep only non-empty lines, remove blank lines). Multiple modes let you use this like a visual grep — include matching lines, exclude matching lines, or filter by length criteria. Perfect for cleaning data, extracting specific content, preparing text for analysis, and working with log files.
Features of Our Filter Lines by Rule
- Filter by text pattern — keep or remove lines containing specific text
- Regex support for advanced pattern matching
- Filter by line length — set minimum and/or maximum character count
- Case-sensitive toggle for precise pattern matching
- Instant results update as you change filters
- Shows counts: total lines, matched lines, filtered lines
- Copy filtered output to clipboard
- 100% private — browser-only processing
How to Use the Filter Lines by Rule
Using this tool is simple and requires no signup or registration. Follow these steps:
- Paste your text into the input area — one line per item.
- Choose a filter mode: "Keep Matching" or "Remove Matching".
- Enter a text pattern, toggle Regex if needed, or set length limits.
- View the filtered output instantly with match counts.
Frequently Asked Questions About Filter Lines by Rule
What is the difference between Keep Matching and Remove Matching?
Keep Matching keeps only lines that match your criteria and removes everything else. Remove Matching does the opposite — it removes lines that match and keeps everything else. This is equivalent to grep -v in Unix.
Can I use regular expressions?
Yes. Toggle Regex mode to use regular expression patterns. For example, ^\d+ matches lines that start with digits, and error|warning matches lines containing either word.
Can I filter by both pattern and length at the same time?
Yes. Both filters are applied together — a line must match the pattern AND the length criteria to be kept (or removed, depending on mode).
Why Choose Text Toolbox?
Text Toolbox provides free, private, and instant online text tools. Unlike other text utility websites that require signup accounts or send your data to servers, all our tools process your text entirely in your browser. This means your content never leaves your device — we cannot see it, store it, or share it. Our tools are fast, lightweight, and work on any device with a modern web browser.