Filter String Lines
Keep or drop the lines of a string that match a pattern. Runs entirely in your browser, so your data never leaves your device.
0 chars · 0 lines
Output
The result appears here as you type.
How to use Filter String Lines
- 1. Paste the multi-line text. Enter the block of text whose lines you want filtered into the input pane, from a short list to a large log file.
- 2. Set the pattern and matching options. Type a Pattern to match, turning on Pattern is a regular expression for regex matching and Case sensitive to control letter-case matching. Turn on Invert to keep the lines that don't match instead.
- 3. Copy the filtered lines. Copy the remaining lines and use them wherever you need just the matching (or non-matching) subset of the original text.
When to use Filter String Lines
Filter String Lines keeps or drops the lines of a string that match a pattern, working like a grep you can run without a terminal. It cuts a large block of text down to just the lines relevant to what you are looking for.
- Isolating error lines from a log file. You pasted a large application log and want only the lines containing 'error' or 'warning' kept, filtering out the routine informational lines that clutter the view.
- Removing blank or comment lines from a config. A config file has blank lines and comment lines starting with '#' mixed in, and inverting a match on that pattern leaves only the active configuration lines.
- Extracting rows matching a specific status. A pasted export has one record per line and you want only the lines mentioning a specific status like 'failed', filtered out from the successful entries.
- Cleaning a URL list down to one domain. You have a long list of URLs and want to keep only the ones from a specific domain, using a regular expression pattern to match just that host.
Examples
Keep lines containing “error”
Input
ok error: 1 error: 2 ok
Output
error: 1 error: 2
About the Filter String Lines tool
Filter String Lines runs as plain JavaScript in your browser tab, with no server behind it. Keep or drop the lines of a string that match a pattern. Whatever you put in stays on your device from start to finish.
The tool is part of EditSafely's String Tools section, 159 single-purpose utilities built around the same idea: open the page, get the result, keep your data to yourself.
You can shape the output with 4 settings, including Pattern, Pattern is a regular expression, Case sensitive and Invert (keep lines that don't match), and the result refreshes the moment you change one. A worked example further down the page shows exactly what the tool produces for a real input.
That local-first design has practical benefits beyond privacy. The tool keeps working on a flaky connection once the page has loaded, results are instant because nothing round-trips to a server, and it is safe to use with confidential material.
Frequently asked questions
Is Filter String Lines free to use?
Yes, it is completely free. All 2,658 tools on EditSafely work without an account, a subscription or usage limits.
Is it safe to paste sensitive or confidential data?
Everything happens locally. Your browser downloads the tool's code once, then does all the processing itself; nothing you enter is transmitted, stored or logged. You can even go offline after the page loads and it will still work.
How much text can I process at once?
There is no fixed limit. Because the work happens on your own device rather than on a shared server, the practical ceiling is your machine's memory, which comfortably handles inputs far larger than typical online tools allow.
Do I need to sign up or install anything?
No. The tool works in any modern browser on desktop, tablet or phone. There is no account to create, no extension to add and no software to install.
How do I use the result?
The output panel has a one-click copy button, and you can keep refining the input while you work; the result updates in place as you type.