Sentence case converter

Paste a paragraph that arrived in all caps, or one typed without any capitals at all, and get it back written normally: one capital at the start of each sentence, everything else left alone.

What sentence case actually means

Sentence case is the way English prose is normally written: the first word of each sentence is capitalised, proper nouns are capitalised, and nothing else is. It is the default for body copy, email, chat, and — increasingly — for headings too, because most style guides now prefer it over title case in interfaces and documentation.

Google, Apple, Microsoft and GOV.UK all specify sentence case for UI labels and headings in their current style guides. If you are writing a button, a menu item or a section heading in a product, sentence case is very likely what the guide you are working to asks for.

The abbreviation problem

The naive way to do this is to capitalise after every full stop. That breaks the moment the text contains e.g., Dr., p.m., Inc. or a URL: "we ship widgets, e.g. blue ones" comes back as "…e.g. Blue ones", which is worse than what you started with.

This converter checks the word attached to each full stop against a list of common abbreviations, and also treats a single letter followed by a stop as an initial — so J. R. R. Tolkien survives intact. A full stop is also only ever treated as a sentence end when whitespace follows it, which is what keeps example.com and 3.14 in one piece.

The remaining ambiguity is genuine and unfixable: in "the call is at 5 p.m. bring the deck", only a reader knows that a new sentence started. The converter takes the abbreviation reading, because getting e.g. right matters more often than the sentence that happens to begin after a time.

Proper nouns will still need a pass

Because everything is lower-cased first, names come back lowercase: "sarah flew to paris on tuesday". No converter can fix that reliably, since telling a name from a common word needs to know what the sentence is about. Word lists get "may" and "march" wrong every time.

The practical workflow is: convert first, then read once for names. That is still far faster than retyping a shouted paragraph, which is the actual alternative.

Worked examples

Run through the same code the button runs, so the examples cannot drift from the tool.

Common questions

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