Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Capitalize the first letter of every sentence in a block of text.
Your result will appear here.
This tool capitalizes the first letter after every sentence-ending punctuation mark (and the very start of the text), without changing the case of anything else -- useful for cleaning up text typed in all-lowercase, or fixing capitalization after merging text from multiple sources.
Paste your text into the input box. The corrected version, with the first letter of each sentence capitalized, appears instantly.
The tool applies two rules and nothing else. First, if the text begins with a lowercase letter (after any leading spaces), that letter is capitalized. Second, wherever a period, exclamation point, or question mark is followed by one or more spaces (or a line break) and then a lowercase letter, that letter is capitalized. Every other character stays as you typed it. Crucially, it never converts capitals to lowercase, so text that is already correctly capitalized, or that contains acronyms and names, passes through untouched.
Suppose you paste this hypothetical text: "thanks for your email. i will send the files tomorrow! can we meet at noon? bring the invoice." The output becomes: "Thanks for your email. I will send the files tomorrow! Can we meet at noon? Bring the invoice." Four sentence starts were fixed and nothing else changed. Now consider "we use NASA data. the results are in." You get "We use NASA data. The results are in." The acronym is preserved because the tool only ever raises a letter, never lowers one.
It shines on text that was typed quickly on a phone with autocorrect off, dictated text that arrived in lowercase, subtitles or transcripts exported without capitalization, or lowercase text produced by the Letter Case Converter earlier in a workflow. It is also useful after you merge notes from several sources, where sentences may start with inconsistent capitalization. A sensible workflow for a rough transcript is to convert the text to lowercase for consistency, run it here, and then manually capitalize names and the pronoun I.
Read the output once, focusing on places where a period appears without ending a sentence: abbreviations, numbered items, and initials. Then scan for names, places, and product names that still need capitals. Finally, look at lists, since a line that ends with a period followed by a line break and a lowercase item will be capitalized, which may or may not suit your list style. A minute of review will catch the small number of mistakes the punctuation rule cannot avoid, and leave you with clean, sentence-case text ready to paste into an email, essay, or document.
No -- it only capitalizes the first letter after sentence-ending punctuation. Proper nouns mid-sentence need to be capitalized manually, since detecting them reliably would require real language understanding, not just punctuation splitting.
No -- everything runs locally in your browser.
No. It only raises lowercase letters at sentence starts and never lowercases anything. To fix all-capital text, first convert it to lowercase with the Letter Case Converter, then run it here.
The rule sees a period followed by a space and a lowercase letter and treats it as a sentence start. It cannot tell an abbreviation from a sentence end, so check abbreviations manually.
It capitalizes a lowercase letter that follows a sentence-ending mark and whitespace, which includes a line break. A new line that follows a line with no ending punctuation is not changed.
Only when "i" starts the text or follows a sentence-ending mark. A standalone "i" in the middle of a sentence is left as typed.