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Capitalize sentences

Automatically capitalize the first letter of every sentence in your text.

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Output
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Capitalize sentences
This tool automatically capitalizes the first letter of every sentence, helping you create grammatically correct text with proper sentence structure. Paste any text and the tool instantly rewrites it with each sentence beginning with a capital letter while preserving everything else exactly as it was. It is ideal for cleaning up text from casual writing, email threads, chat messages, or any source where capitalization conventions were not followed.
Sentence boundaries are detected after periods (.), question marks (?), and exclamation marks (!), but only when followed by whitespace. For example, "hello. world" becomes "Hello. World", while "hello.world" stays as "Hello.world" because the period is not followed by a space. When a sentence starts with non-letter characters like numbers or symbols, the tool skips those and capitalizes the first actual letter found, so "hello. 123 world" becomes "Hello. 123 World". If a letter is already uppercase, it stays unchanged—there is no risk of unwanted changes to acronyms or proper nouns within sentences.
Everything runs entirely in your browser with no uploads or external processing, making it safe for confidential content. The live tally under the output counts how many sentences were detected and displays the total character count. You can copy the result, download it as a plain text file, or pass it to another tool for further editing. This makes it perfect for fixing grammar in informal text, preparing documents for publishing, or standardizing capitalization across multiple sources.
FAQ
What counts as a sentence boundary?
A new sentence starts at the beginning of the text or immediately after a period, question mark, or exclamation mark that is followed by whitespace. Without whitespace after the punctuation, no new sentence is recognized—for example, "file.txt" is treated as one sentence.
What if a sentence starts with a number or symbol?
The tool skips non-letter characters and capitalizes the first actual letter it finds. So "hello. 123 world" becomes "Hello. 123 World", with the first letter of "world" capitalized.
Does it change already uppercase letters?
No. If a letter is already capitalized, it remains unchanged. This prevents unintended changes to acronyms, brand names, or any intentionally uppercase text within sentences.
Is my text uploaded anywhere?
No. The capitalization runs entirely in your browser and your text never leaves your device.