⌘ K
literal · regex · keep / remove

Filter lines by match or exclude

Grep-like keeper or remover. Literal substring or regex, case-sensitive or insensitive.

Line Filter Workspace
Input lines
6
106 B
Matched
2
kept
Output lines
2
42 B
Mode
literal
aa
input · lines
output · filtered
ERROR: db connection failed
ERROR: timeout
Quick Start

How to filter lines

Like grep in the browser. Literal substring matches by default; switch to regex for pattern-based filtering.

  1. 01

    Paste lines

    Any text — logs, lists, exports.

    Tokenisation is Unicode-aware via \p{L}\p{N} property classes — so accented letters, ideographs, and emoji code points all count correctly.

    anyUTF-8Unicodecode pointslive
    input · textraw · UTF-8
    INFO
ERROR
WARN
    loaded · UTF-8UTF-8 · ready
  2. 02

    Set pattern

    Literal substring (case-insensitive by default) or regex (use ^ and $ for line anchors).

    Live re-counts run on every keystroke through a memoised reducer, so even multi-megabyte inputs stay smooth in the editor.

    literalregexlivememoisedoptions
    pattern · optionsERROR · live
    /ERROR/i
    options applied · livelive
  3. 03

    Keep or remove

    Keep matching lines (grep) or remove them (grep -v).

    Output preserves the original line endings (\n vs \r\n) and trailing whitespace is reported separately so you can spot diff-only changes.

    grepgrep -vline endingswhitespacediff-clean
    action · countedkeep · ready
    ERROR: timeout
ERROR: db
    counted · livecounted
  4. 04

    Copy or download

    One click.

    Copy writes via the Async Clipboard API; downloads ship as text/plain; charset=utf-8 — nothing leaves your tab.

    copyclipboardtext/plainblobclient-side
    export · copiedready · done
    ✓ Copied
    shipped · ready to shipsuccess
Pro tips

Text-processing fundamentals worth knowing

Tokenise with Unicode classes

Use \p{L}\p{N} with the u flag so accents, ideographs, and emoji count properly.

Normalise line endings

Convert \r\n to \n before diffing or hashing — Windows-vs-Unix endings produce phantom changes.

Mind invisible characters

Zero-width joiners, BOMs, and non-breaking spaces look identical to ASCII space. Strip them before comparison or storage.

Stream don’t slurp

For multi-megabyte text, iterate line-by-line rather than loading everything to memory — keeps the tab responsive.

Choose collation deliberately

Default JS sort is code-point order, not human alphabetical. Use Intl.Collator for locale-aware sorting.

Re-run after normalisation

NFC vs NFD changes byte length but not visible glyphs. String.prototype.normalize() before counts and comparisons.

Related toolsFind & ReplaceRemove DuplicatesSort LinesMerge ListsColumn ExtractorRegex Tester
Use Cases

When to filter lines

Anywhere you'd run grep.

Log triage

Keep only ERROR or WARN lines. Tokenisation uses Unicode property classes (\p{L}, \p{N}) with the u flag so accents, ideographs, and emoji code points all count correctly. Surrogate-pair-aware counts mean 🚀 weighs 1, not 2.

Unicode-correct

Email list cleanup

Remove all lines containing certain domain. Result updates as you type — paste and watch totals settle in milliseconds even on multi-megabyte inputs. Heavy work runs through a memoised reducer so the editor never janks.

diff-clean

URL filtering

Keep only URLs matching /blog/ path.

instant counts

Test fixtures

Filter test cases by tag or category. Code-point counts are stable across NFC/NFD normalisation. Pair with the Reading Time Calculator to layer scan-time on top of raw counts, useful for editorial budgets and SEO meta-description limits.

platform-aware

Code comments

Filter source to just // TODO lines. All processing runs client-side — paste sensitive or pre-publish copy without it leaving the tab. The clipboard API writes UTF-8 text/plain so it survives transit to any editor or CMS.

code-point-accurate

Allowlist filter

Remove blocked entries from a list. Same input plus same options always produces identical output, so the tool is safe to embed in CI scripts or doc-generation pipelines without race conditions.

lossless
FAQ

Frequently asked questions

Literal escapes regex metacharacters. Regex treats them as patterns. Use literal unless you need pattern matching.
Each line is matched independently. For multi-line patterns, use a different approach (e.g. JS regex with /s flag in a custom tool).
Anything separated by \n. Empty lines count as lines (you can decide to keep or remove them based on pattern matching).
No. All processing runs locally.
Yes — use Remove matching (like grep -v).
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