Skip to main content
Z

Filter Lines — Online Grep to Keep or Remove Matching Lines

Keep or remove lines matching a substring or regex pattern. Invert match, case-insensitive, trim before match.

Free No signup Client-side Privacy friendly Updated

How to use

  1. 1 Paste lines on the left and a pattern below.
  2. 2 Toggle Keep matching (default) or Remove matching.
  3. 3 Switch on Regex for full regular expression power, with i / m / u / s flag toggles.
  4. 4 Copy the filtered result.

Why use this tool

  • Plain substring match by default — no regex special-character traps.
  • Regex mode with the four most-used JS flags exposed as checkboxes.
  • Invert match flips just the match, leaving Keep/Remove logic intact.
  • Bad regex shows inline, never crashes the page.

Frequently asked questions

What is the difference between Invert match and switching Keep/Remove?

They are equivalent — "Remove matching X" is the same as "Keep + Invert match on X". The two controls just make common phrasings ("keep lines that do NOT contain", "remove lines that do NOT contain") quick to express.

What do the regex flags do?

i = case-insensitive, m = multiline (^ and $ match each line), u = full Unicode, s = dot matches newline. We always run per-line so m has limited effect here; useful when your pattern itself spans newline-escaped sequences.

How does Trim before match interact?

The line is trimmed only for the match decision; output lines keep their original leading/trailing whitespace.

Related tools?

Use Deduplicate Lines to drop duplicates, or Sort Lines to reorder after filtering.

What is Filter Lines?

A Filter Lines tool is a tool that keeps or removes lines of text matching a substring or regular expression pattern. It supports inverting the match, case-insensitive comparison, and trimming each line before matching. Running entirely in the browser, it works like an online grep for filtering text, letting users find and remove lines containing specific content without sending data to a server.

Features

Keep or remove matches

Show only matching lines, or drop them, with an invert toggle.

Substring or regex

Match a plain substring or a full regular expression with i / m / u / s flags.

100% private

Runs on your device — your text is never uploaded.

Example

Input

apple
banana
apricot   (keep lines containing "ap")

Output

apple
apricot

Common use cases

  1. 1

    Grep pasted text

    Filter a log or list down to the lines containing a term or pattern.

  2. 2

    Remove unwanted lines

    Drop comment lines, blanks, or entries matching a pattern.

  3. 3

    Extract structured rows

    Keep only lines matching a regex (e.g. emails, IPs) from mixed text.

Summary

Zerethon's filter-lines tool keeps or removes lines that match a substring or regular expression, in your browser. It supports regex flags (i, m, u, s), an invert option, and trim-before-match — ideal for grepping through pasted text. Everything runs client-side; nothing is uploaded.

Category
Creator
Pricing
Free
Privacy
Browser-based
Signup
Not required

References

Privacy

Your data never leaves your browser unless explicitly stated. Filter Lines runs entirely client-side — no server upload, no logging, no tracking of your input.

Related tools

YouTube Thumbnail Downloader

Download YouTube thumbnails in all available resolutions. Just paste a video URL.

Open tool

Open Graph Preview

Test how your URL appears when shared on social media. Preview Facebook, Twitter, LinkedIn, and Slack cards.

Open tool

Word & Character Counter

Count words, characters, sentences, and paragraphs. Reading time, speaking time, and top keywords — instant.

Open tool

Lorem Ipsum Generator

Generate Lorem Ipsum placeholder text — by paragraphs, sentences, or words. Optional HTML wrapping.

Open tool

Build, share, and grow on Zerethon Social

Free signup. Earn points, collect achievements, and connect with creators worldwide.

Try Zerethon free