Grep a String
Keep the lines of a string that match a regular expression. 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 Grep a String
- 1. Paste your text. Enter the multi-line text you want to filter into the input pane. Each line is tested independently against the pattern you provide.
- 2. Enter a regular expression and flags. Type the pattern in Regular expression and any modifiers, like i for case-insensitive, in Flags. Only lines that match the pattern are kept by default.
- 3. Adjust invert and match-only behavior. Turn on Invert to keep lines that don't match instead, or check Output only the matched fragments to return just the matching substring rather than the whole line.
- 4. Copy the filtered lines. Copy the surviving lines from the output pane into your log analysis, report or follow-up processing step.
When to use Grep a String
Grep a String filters a block of text down to the lines matching a regular expression, doing in the browser what the grep command does in a terminal. It handles log filtering, quick text searches and one-off data cleanup without opening a shell.
- Filtering an error log. You pasted a large application log and want only the lines mentioning ERROR or WARN. A pattern like ERROR|WARN with the i flag pulls out just those entries for review.
- Extracting email addresses from notes. A block of meeting notes has scattered email addresses mixed with other text. Checking Output only the matched fragments with an email regex returns just the addresses, one per line.
- Excluding blank or comment lines. A config file has comment lines starting with # that you want to ignore while reviewing the active settings. Matching ^# and inverting the result keeps everything except comments.
- Isolating lines with a specific status code. A CI log lists dozens of test results and you only care about the ones that returned status 500. Grepping for 500 quickly narrows a long console dump to the relevant lines.
Examples
Keep lines containing a digit
Input
abc a1 xyz b2
Output
a1 b2
About the Grep a String tool
Grep a String is a free online tool that works entirely inside your web browser. Keep the lines of a string that match a regular expression. Because the processing happens on your own device, nothing you enter is uploaded, logged or stored anywhere.
This page is one of 159 String utilities on EditSafely. Each one does a single job well, and all of them follow the same rule: your input stays on your machine.
You can shape the output with 4 settings, including Regular expression, Flags, Invert (keep lines that don't match) and Output only the matched fragments, 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.
Because nothing leaves your device, the tool is suitable for sensitive content such as internal documents, credentials or customer data. It also responds instantly, since every keystroke is handled on your own machine rather than by a remote API.
Frequently asked questions
Is Grep a String 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.