Sentence Case Converter

Capitalise only the first word of each sentence

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Sentence case is the natural way we write prose: lowercase throughout, with only the first word of each sentence capitalised. This converter is most useful for fixing text that arrived in ALL CAPS or random mixed case, turning it back into readable sentences.

How it works

The converter first lowercases the entire input, then walks through it and capitalises the first letter that follows a sentence boundary:

  • the start of the text
  • a sentence-ending mark (., !, or ?) followed by space
  • the start of a new line

After that, the standalone pronoun I and its contractions (I'm, I'll, I've, I'd) are restored to uppercase so the result reads correctly.

Example and notes

THIS IS A SHOUTING SENTENCE. and here is another one! becomes This is a shouting sentence. And here is another one!. Because the tool has no dictionary of names, proper nouns such as cities, people, and brands are lowercased and will need a manual fix — sentence case handles structure, not semantics.

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