How to use it
- Paste your lines or open a file.
- Choose Keep only these or Remove these.
- Pick a condition and type what to look for.
- Copy or download the filtered lines.
Conditions
| Condition | Matches lines that… |
|---|---|
| Contains | include the text anywhere |
| Starts with | begin with the text |
| Ends with | end with the text |
| Exact line | are exactly the text, nothing more |
| Regular expression | match a JavaScript regex pattern |
Then choose what to do with the matches: Keep only these (like grep) or Remove these (like grep -v).
The note under the result shows how many lines matched and how many were kept.
Options
- Multiple terms separated by commas (any). Type
gmail, yahoo, outlookto match lines containing any of the three. Semicolons and pipes work as separators too. Not available in regex mode, where you'd writegmail|yahoo|outlookinstead. - Ignore case. On by default, so
gmailalso matchesGMAIL.com. - Whole words only (Contains mode).
catmatches the cat sat but not category. - Remove empty lines. Blank lines are dropped from the result.
With regular expressions, case sensitivity follows the Ignore case option, and the pattern is tested against each line separately, so ^ and $ mean the start and end of the line.
Examples
| Goal | Settings |
|---|---|
| Only Gmail addresses from a list | Keep · Contains · gmail |
| Drop comment lines from a config file | Remove · Starts with · # |
| Lines that start with a number | Keep · Regex · ^\d+ |
| Error lines from a log | Keep · Contains · ERROR, FATAL with multiple terms |
| Remove .png and .gif files from a file list | Remove · Ends with · .png, .gif with multiple terms |
| Lines with a US ZIP code | Keep · Regex · \b\d{5}(-\d{4})?\b |
Text you filter stays in your browser, so it's safe to use with server logs, customer lists and other private data.
Step-by-step: pulling errors from a log
- Open the log file with Open file, or paste the lines.
- Choose Keep only these and Contains.
- Turn on Multiple terms and type
ERROR, WARN. - Click Use result as input.
- Switch to Remove these and type
healthcheckto drop noisy lines. - Download the result.
The note after each step tells you how many lines matched, so you can see the effect of every filter.
Combine with other tools
Filtering is often one step in a cleanup:
- Remove extra spaces so stray spaces don't break starts with and ends with matches.
- Filter the lines here.
- Remove duplicate lines and sort lines in the result.
- Count the lines or join them into one line with the comma separator.
To change text inside lines instead of keeping or dropping whole lines, use find and replace. Use Use result as input to apply a second filter on top of the first, for example keep lines with ERROR, then remove lines with timeout.
Files
Click Open file to load .txt, .csv, .log or .md files and Download to save the result. Very large logs (several megabytes) work too, because the filtering runs locally.
Frequently asked questions
How do I remove lines that contain a word?
Choose “Remove these”, set the condition to Contains, and type the word.
How do I keep only lines that contain certain text?
Choose “Keep only these” with Contains and type the text. Use the multiple terms option to match any of several words.
Can I use regular expressions?
Yes. Choose Regular expression; the pattern is tested against each line, and Ignore case applies.
Is the filter case-sensitive?
Not by default. Turn off “Ignore case” for case-sensitive matching.
Can I filter a large log file?
Yes. Open the file or paste it; filtering runs in your browser, even for large files.
Last updated: November 12, 2026