Add line numbers to text
Prefix every line with a sequential number. Configurable start, zero-padding, and separator.
01 | first line 02 | second line 03 | 04 | fourth line (after blank) 05 | fifth line
How to number lines
Adds a sequential number to every line with configurable formatting.
- 01
Paste text
Code snippets, lists, or any multi-line content.
Tokenisation is Unicode-aware via
\p{L}\p{N}property classes — so accented letters, ideographs, and emoji code points all count correctly.linesUTF-8Unicodecode pointsliveinput · textraw · UTF-8first second
loaded · UTF-8UTF-8 · ready - 02
Pick start & padding
Start at 1, 0, or anywhere. Pad with zeros to a fixed width.
Live re-counts run on every keystroke through a memoised reducer, so even multi-megabyte inputs stay smooth in the editor.
startpadlivememoisedoptionsconfig · options01·02 · live01 | first 02 | second
options applied · livelive - 03
Separator
Default
|. Try.,:,\\tfor tab.Output preserves the original line endings (
\nvs\r\n) and trailing whitespace is reported separately so you can spot diff-only changes.customline endingswhitespacediff-cleanreproduciblesep · counted | · ready01. first
counted · livecounted - 04
Skip blanks?
Off by default. Enable to leave empty lines un-numbered.
Copy writes via the Async Clipboard API; downloads ship as
text/plain; charset=utf-8— nothing leaves your tab.skipclipboardtext/plainblobclient-sidepolicy · copiedset · done✓ Copied
shipped · ready to shipsuccess
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.
When to number lines
Anywhere line references matter.
Code snippets
Add numbers before pasting to chat or docs. 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-correctEditor notes
Number each note for reference in discussion. 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-cleanTest cases
Number test cases for issue links. Output normalises line endings to LF for clean diffs across platforms. Windows-vs-Unix CRLF mismatches disappear, which keeps git blame honest and review comments focused on real changes.
instant countsLyrics / poetry
Number verses or stanzas. 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-awareTODO lists
Sequentially number a TODO for prioritization. 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-accurateLegal docs
Number paragraphs for citation. 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.
losslessFrequently asked questions
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