What defines a sentence boundary?

Sentence boundaries are detected at periods, exclamation marks, and question marks followed by whitespace. The first letter after each boundary is uppercased.

Does it lowercase the rest of the text?

Yes. By default the rest of each sentence is lowercased, so SHOUTING text and Mixed Case both become standard sentence case.

Are proper nouns preserved?

No. The converter has no dictionary, so names like "London" or "Anthropic" will be lowercased and must be re-capitalised manually if needed.

Is my text uploaded anywhere?

No. The conversion runs locally in your browser; the text never reaches a server.

first-letter capitalization · per-sentence

Convert to Sentence case

Lowercase everything, then capitalize the first letter of each sentence. Standard prose convention.

Sentence case Workspace

Input size

46 B

8 words

Output size

46 B

sentence-cased

Sentences

auto-detected

Convention

Sentence

first letter caps

input · text

output · Sentence case

Hello world. This is a test. Another sentence!

Quick Start

How to convert to Sentence case

The most natural convention for prose. The tool lowercases everything, then capitalizes the first letter of each sentence (first character, plus characters following ., !, or ?).

01
Paste text
All-caps, mixed-case, or anywhere in between.
Tokenisation is Unicode-aware via \p{L}\p{N} property classes — so accented letters, ideographs, and emoji code points all count correctly.
any caseUTF-8Unicodecode pointslive
input · textALL CAPS · UTF-8
```
HELLO. WORLD.
```
loaded · UTF-8UTF-8 · ready
02
Auto-lowered + capitalized
Everything becomes lowercase, then sentence starts get capitals back.
Live re-counts run on every keystroke through a memoised reducer, so even multi-megabyte inputs stay smooth in the editor.
livememoisedoptionssnappy
output · optionssentence case · live
```
Hello. World.
```
options applied · livelive
03
Sentence detection
Splits on ., !, ? followed by whitespace. Acronyms and abbreviations may not split correctly.
Output preserves the original line endings (\n vs \r\n) and trailing whitespace is reported separately so you can spot diff-only changes.
heuristicline endingswhitespacediff-cleanreproducible
rules · countedapplied · ready
```
Two sentences. One conversion.
```
counted · livecounted
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.

Use Cases

When to Sentence case

Anywhere prose belongs.

Body copy

Standard prose convention for blog body, descriptions, emails. 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

Normalize ALL CAPS

Fix forwarded emails or angry chat messages. 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

Subtitles

Convert all-caps subtitles to natural Sentence case. 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 counts

OCR cleanup

Convert OCR all-caps output to readable prose. 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

Database records

Normalize user-entered names with random casing. 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

Microcopy

UI labels and tooltips in friendly Sentence case. 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

Does it handle abbreviations?

Heuristically. Mr. Smith may split incorrectly if followed by a capitalized word.

What about proper nouns?

They're lowercased too — re-capitalize names by hand after.

Is the first letter always capitalized?

Yes — even if the input doesn't start with a letter.

Is anything sent to a server?

No. All processing runs locally.

What about acronyms?

They lose their capitalization. Use Find & Replace to restore them.

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