Sentence Case Converter
Sentence Case Converter lowercases the complete input, then uppercases the first Unicode letter and letters following period, exclamation mark, or question mark plus whitespace. It does not recognize abbreviations, decimals, quotes before the next letter, sentence boundaries without terminal punctuation, or new lines as independent sentences unless the regex conditions are met. Acronyms and proper nouns lose their original casing.
Runs locally — files stay on your deviceDoes every new line start with a capital?
Not necessarily. The rule is based on start or .!? followed by whitespace.
Sentence segmentation is language-sensitive
Reliable boundaries require abbreviation, punctuation, quotation, and language context; this page uses a compact punctuation heuristic.
How it works
String.toLowerCase runs first, then a regex uppercases a Unicode letter at the start or after .!? and whitespace.
Key concepts
Everything lowers first
NASA becomes Nasa unless manually restored.
Punctuation heuristic
A period in an abbreviation can trigger a capital.
When to use it
- Normalize simple prose sentences.
- Remove random internal capitals.
- Create a draft for manual proofreading.
When not to use it
- Do not expect abbreviation-aware segmentation.
- Do not preserve names or acronyms.
- Do not use it as grammar correction.
Worked examples
Simple
- Input
hELLO WORLD. nEXT ONE!- Expected output
Hello world. Next one!
Terminal punctuation works.
Name
- Input
meet ANA.- Expected output
Meet ana.
Proper-noun casing is lost.
Line break
- Input
first\nsecond- Expected output
First\nsecond
A newline alone does not match the sentence-start rule.
Common mistakes
Expecting grammar analysis
Only casing changes. Correction: Proofread separately.
Losing names
Whole input lowers. Correction: Restore proper nouns.
Assuming line starts
Newline is insufficient alone. Correction: Handle lines separately if required.
Best practices
- Use on simple prose.
- Restore acronyms and names.
- Proofread boundaries and abbreviations.
Related operations and differences
Capitalize Every Word
Choose Capitalize Every Word when you need to capitalize the first character of every word.; use Sentence Case Converter specifically for sentence case.
Add Prefix to Every Line
Choose Add Prefix to Every Line when you need to add the same prefix before every line.; use Sentence Case Converter specifically for sentence case.
Add Suffix to Every Line
Choose Add Suffix to Every Line when you need to add the same suffix after every line.; use Sentence Case Converter specifically for sentence case.
Extract Email Addresses
Choose Extract Email Addresses when you need to find unique email addresses in text.; use Sentence Case Converter specifically for sentence case.
Extract URLs
Choose Extract URLs when you need to find unique HTTP and HTTPS links in text.; use Sentence Case Converter specifically for sentence case.
Line Counter
Choose Line Counter when you need to count the number of text lines.; use Sentence Case Converter specifically for sentence case.
Limitations and privacy
- Lowercase plus .!? whitespace heuristic; no language model, abbreviation list, newline mode, quote handling, proper-name dictionary, grammar, or locale selector.
Text is transformed locally in this browser and is not uploaded by the tool.
Frequently asked questions
Are acronyms preserved?
No.
Does it fix punctuation?
No.
Are new lines capitalized?
Not merely because they are new lines.
Does Romanian text work?
Unicode letters are supported by the casing step.