What this tool does
Most online case converters lowercase everything, capitalise the first letter of each word, and destroy your text: YouTube becomes Youtube, iPhone becomes Iphone, and the US in "the US military" becomes Us. The rules behind real title case are a set of editorial tables and one judgement call, and this tool implements them, shows you the words it decided were interesting, and lets you add the brands and acronyms you actually use.
How it works
Two decisions shape the whole thing. First, the exception list is applied before the case transform, not after: iPhone, eBay, macOS, pH, HDFC and SBI are looked up in their written form and reinserted unchanged, so nothing is lost to a lowercasing pass. A pipeline that lowercases and then capitalises cannot recover a brand, because the evidence has already been destroyed by the time it needs it. Second, an acronym is decided by the shape of the word as you wrote it, never by what it means. A run of two to five capitals that is not a common English word is an acronym and survives; a lowercase us stays a word, because nothing in the text can say whether it is a pronoun or a country. That is why "Let Us Know the US Military Said Us" is the correct AP answer and "Let Us Know the Us Military Said Us" is the one every naive converter gives you.
Title case is a style, not a standard, and the two commonest styles disagree on exactly the words people argue about. AP lowercases articles, coordinating conjunctions and prepositions of fewer than four letters, so from, over and with are capitalised and in, on and of are not. Chicago lowercases every preposition at any length, so from and over drop down too. "Walking Home From School Over a Bridge With a Friend in the Rain" becomes "Walking Home from School over a Bridge with a Friend in the Rain" under Chicago. Both are correct, for different style guides, and a tool that picks one without saying so is making the decision for you.
The identifier styles are deliberately not the prose rules. camelCase, snake_case, kebab-case, dot.case and CONSTANT_CASE drop the exception list on purpose, because iPhone carries no meaning inside a variable name and splitting it into i_phone helps nobody — "convert HTTP server for iPhone users" becomes convert_HTTP_server_for_i_phone_users, which is ugly but predictable. They do keep a source acronym, because dropping HTTP from a name loses information you deliberately put there. The word splitter itself is segment-aware, so convertHTTPServerForIPhoneUsers, h264, version_2 and u.s.a. all come apart at the right places rather than at every capital.
The tool also reports why each word came out the way it did, and only for words where the reason is information: protected exceptions, acronyms kept as written, small words left lower, sentence starts, dotted initialisms folded back into one token, and short tokens that a reader might mistake for an acronym. Words that were simply capitalised are not listed, because that is not news. It runs entirely in the browser, and the exception list is editable, because the built-in one is a starting point covering common English brands and Indian financial abbreviations rather than a complete dictionary of every capitalisation anyone has ever invented.
Worked example
Turning a mixed-case draft sentence into an AP title, a Chicago title, sentence case and a JavaScript identifier.
- Input: "let us know the US military said us. it's a u.s.a. issue — see the CEO's note about iPhone sales in Q3 (up 24% from 2024)."
- AP keeps in, a and the lower, holds US and CEO as written, protects iPhone, and folds u.s.a. into one initialism: "Let Us Know the US Military Said Us. It's a U.S.A. Issue — See the CEO's Note About iPhone Sales in Q3 (Up 24% From 2024)."
- Chicago differs only in the small words: "...Note about iPhone Sales in Q3 (Up 24% from 2024)" — about and from drop down
- Sentence case lowercases the line and capitalises the first word, keeping US because it was written in capitals: "Let us know the US military said us. it's a U.S.A. issue — See the CEO's note about iPhone sales in q3 (Up 24% From 2024)."
- convertCase('convert HTTP server for iPhone users', 'camel') gives convertHTTPServerForIPhoneUsers — HTTP survives, iPhone is tokenised into i and Phone
Six different outputs from one input, each traceable to a specific rule, and every internal capital in a brand or acronym survives all of them.
Accuracy and limitations
- Title case has no single correct answer. AP and Chicago genuinely disagree on prepositions, and a house style guide may disagree with both, so check the first and last words and any proper noun against your own guide before publishing.
- Brand internal capitals only survive if you list them. The default exception list covers common English brands and Indian abbreviations, not every product name in existence, and nothing here can guess that a word you typed as "netflix" was meant to be a brand.
- A lowercase us is always read as a word, and a US is always read as an acronym, whatever the surrounding sentence meant. That is the only defensible rule without a dictionary, but it means a sentence where you typed us to mean the country will be left lowercase.
Frequently asked questions
- What is the difference between AP and Chicago title case?
- AP lowercases prepositions of fewer than four letters, so in, on and of stay down but from, over and with are capitalised. Chicago lowercases every preposition at any length, so from, over and about drop down too. Both capitalise the first and last word, and neither is wrong — they are two style guides answering the same question differently.
- How do you title case a sentence with acronyms?
- Write the acronym in capitals and the converter will keep it, because an acronym is judged on how it was written rather than on what it means. "the US military" comes out as "the US Military", not "the Us Military". The exception list protects the same way for brands, so a lowercase "iphone" needs adding to the list before it will come back as iPhone.
- How do I convert camelCase to snake_case?
- Use the snake_case tab. The converter splits on the humps inside a word as well as on spaces and underscores, so convertHTTPServerForIPhoneUsers becomes convert_HTTP_server_for_i_phone_users. A source acronym is deliberately kept in capitals, because dropping HTTP from a name loses information, but the brand exception list is ignored here since iPhone has no meaning inside an identifier.
- Why did it turn iPhone into Iphone?
- Because the word was not on the exception list. Exceptions are matched before the transform, so a brand that has internal capitals only survives if you list it. Add iPhone to the exception box and it comes back intact through every style, including lowercase and uppercase. The built-in list is a starting point, not a dictionary of every capitalisation anyone has ever invented.
- Why is us lowercase but US capitalised?
- Because the tool decides acronyms by shape, not by meaning. A run of capitals that is not a common English word is treated as an acronym and kept; a lowercase us is left as a word. Nothing in the text alone can tell a pronoun from a country, so a lowercase us that you meant as the United States stays lowercase. This is the one case where the rule is visible rather than silent.
- Can I convert to uppercase for a spreadsheet?
- Yes, and you do not need a separate tool for it. The UPPERCASE tab uppercases the whole text while still applying the exception list, so acronyms and brands keep their internal capitals instead of becoming IPHONE. For a whole CSV column rather than a pasted block, the CSV cleaner has a column-wise case mode that does the same job per cell.