Case Converter

How to use the case converter

1. Paste or type your text in the box, or use Open file for a .txt, .csv or .md file. Example loads a sample.
2. Under Convert to, pick one of the 12 cases. The result updates as soon as you choose or type.
3. Click Copy or Download .txt to take the result with you.
4. To chain two conversions, click Use as input: the result moves to the input box and you can pick another case. Undo brings the earlier text back.

The links under the result open the same text in the title case converter, the word counter or the extra space remover.

The 12 cases

Each row shows the result for the input user ID from the XMLHttpRequest.

lowercase, UPPERCASE, aLtErNaTiNg and iNVERSE change letters only: spaces, punctuation, digits and emoji stay where they are. The alternating pattern counts letters only, so it carries on across spaces and punctuation instead of restarting with each word.

Acronyms, brand names and emails

Sentence case, Capitalized Case and Title Case keep words that are written in a special way, so you do not lose them when you fix the rest of the text:

• Acronyms of two or more capitals: NASA, ID, IT, also with a possessive (CEO’s), dotted initialisms such as U.S., and capitals mixed with digits (Q3, 4K).
• Mixed-case names: iPhone, eBay, XMLHttpRequest, O’Brien. Sentence case leaves them as typed even at the start of a sentence (iOS and macOS updates.).
• Email addresses and links: [email protected] stays as typed.

The last two rows show the two limits. A run of neighbouring all-caps words counts as shouting and is lowercased when one of them has five or more letters (HELLO WORLD), when it has three or more words (THIS IS A TEST), or when it has two words and one of them has four or more letters (STOP NOW, NASA FBI). Short acronyms side by side (FBI CIA) or separated by a comma (PDF, DOCX) are kept, and so is a single all-caps word (IT) among lowercase words. Text with no lowercase letters at all is treated as shouting throughout, so NASA becomes nasa. Sentence case keeps capital initials and a capitalized word after an initial or a capitalized Mr., Dr. and similar titles (J. K. Rowling, Mr. Smith), but lowercases the title itself mid-sentence (we met Mr. Smith → We met mr. Smith). Other names, and names typed in lowercase (dr. smith), are not recognized; capitalize them by hand. The UPPERCASE, lowercase and programmer cases convert every word, acronyms included.

How sentences and titles are decided

Sentence case starts a new sentence after ., !, ? or …, also when a closing quote or bracket follows, and after an empty line. After ! or ? plus a closing quote, a word typed with a lowercase first letter continues the sentence: He said “stop!” and left. stays as it is. Abbreviations such as Dr., Mr., etc., e.g. and i.e. and single initials do not end a sentence. A sentence that starts with a digit is left alone (3rd place.). The word I and its contractions (I’m, I’ve, I’d, I’ll) are always capitalized. A single line break does not start a sentence, so in a list only the first line is capitalized; use the sentence case converter for more control, or Capitalized Case for one-word lines.

Title Case (APA) treats each line as a separate title. The first and last word, the first word after a colon, period, question mark, exclamation mark or em dash, and the word before a colon, question mark or exclamation mark are always capitalized (What Is It For: A Guide). In the middle, the tool keeps these words lowercase: a, an, the, and, as, at, but, by, for, if, in, nor, of, off, on, or, out, per, so, to, up, via, yet. Every other word is capitalized, including longer prepositions such as from and between, and both parts of a hyphenated word (Self-Report). A word or hyphen part that starts with a digit keeps its letters lowercase (Over-40s). Roman numerals from II to XXXIX are written in capitals (world war ii → World War II); Capitalized Case does not do this and gives World War Ii. The tool cannot see grammar, so a short word used as an adverb, as in Turn Caps Lock on Before Typing, stays lowercase when it should not. The title case rules guide compares APA with AP, Chicago and MLA.

How the programmer cases split words

camelCase, PascalCase, snake_case, kebab-case and CONSTANT_CASE first break the text into words, then join them. A new word starts at:

• any character that is not a letter or digit: space, _, -, ., /, :, #, brackets and emoji (these are removed, except that snake_case and CONSTANT_CASE keep underscores at the start and end of a line, so _private and __init__ stay as they are);
• a capital letter after a lowercase letter or digit (userName → user, Name);
• the last capital of a run of capitals followed by lowercase (HTMLString → HTML, String), unless a digit follows that lowercase letter (IPv6 stays one word: ipv6_address).

That means you can convert between programmer cases directly, and acronyms inside identifiers are normalized:

Each line is converted separately and empty lines are kept, so a column of labels pasted from a spreadsheet becomes a column of field names:

first name        firstName
last name    →    lastName
email address     emailAddress

Apostrophes (’ and ’) are dropped before splitting, so don’t stop becomes dontStop and dont_stop, and John’s book becomes johnsBook; a name such as O’Brien stays one word (obrien). One lowercase letter followed only by capitals stays one word (iOS app → iosApp, ios_app), but iPhone15Pro still splits into i_phone15_pro, because real identifiers such as xAxis have the same shape; fix such names by hand. Before you paste the result into code, also check accents: accented letters are kept (café crème becomes caféCrème), which some languages and systems do not accept in names; the slug generator gives a plain ASCII result for URLs. The camelCase vs snake_case vs kebab-case guide explains which convention each language and tool expects.

When people use it

• Fixing caps-lock text: an email, a form answer or a product description typed in capitals, turned into sentence case in one step.
• Headlines and headings: blog titles, slide headings and email subject lines in Title Case or Sentence case, so a whole list follows one style.
• Spreadsheet and CRM headers: column names such as First Name turned into first_name for a database import or firstName for a JSON field.
• Code and config: renaming a list of constants to CONSTANT_CASE, or CSS class names and file names to kebab-case.
• Social posts: aLtErNaTiNg case for the mocking meme style, or UPPERCASE for a short label.

Questions