Case Converter

A case converter changes how letters look, not what they spell

Paste English text into the converter above and every format appears at once: six writing styles (UPPER CASE, lower case, Sentence case, Title Case, Capitalized Case and iNVERSE cASE) and six programming styles (camelCase, PascalCase, snake_case, CONSTANT_CASE, kebab-case and dot.case). Click a card to load that format into the result box, or press the copy button on the card to copy the whole result straight away. Digits, punctuation and writing systems without capitals, such as Korean or Japanese, are left as they are.

Title Case is the format people get wrong most often, and the one most online converters treat as “capitalize everything.” Real style guides do not: they keep articles, short prepositions and some conjunctions lowercase, and they disagree about which ones. Take a guide to cooking with kids. APA 7 gives A Guide to Cooking With Kids, because with has four letters. Chicago 18 gives A Guide to Cooking with Kids, because it still treats with as a short preposition. The word check strip under the result shows why each word got its capital or its lowercase.

When you need to change case

• Formatting a headline, paper or slide title: journals, publishers and style sheets ask for a specific title style. Pick APA 7 or Chicago 18 under Title Case and the minor words are lowercased by that guide’s own list.
• Fixing text typed with Caps Lock on: if you hold Shift for the first letter while Caps Lock is on, you get hELLO, MY NAME IS jIHO. The iNVERSE cASE card turns it into Hello, my name is Jiho without retyping.
• Making ALL CAPS text readable: notices, subtitles and old database exports are often entirely in capitals. Sentence case keeps only the first letter of each sentence in capitals; you then click proper nouns such as names and places to restore them.
• Normalizing a list before sorting or de-duplicating: after everything is lower case, Apple and apple are the same value.
• Naming things in code: type user profile image URL and compare userProfileImageUrl, user_profile_image_url and user-profile-image-url side by side. To rename an existing getUserName to get_user_name, paste it and copy the snake_case card.

How to use it

1. Paste your text into the box, or open a .txt file with the button or by dropping it onto the box. The box starts with an article-title example, and the Examples buttons load a Caps Lock mistake, a set of code names and a sentence.
2. Compare the cards. Each shows the start of your text in that format, and its copy button takes the full result.
3. Click a card to load it into the result box. Letters that differ from your text are marked, and when you switch formats only the changed letters slide into place.
4. For Title Case, choose a title style. For Sentence case, Title Case and Capitalized Case, turn “Keep acronyms and brand spellings” on or off. For code names, choose whether each line becomes its own name or all lines join into one.
5. If a word in the word check strip is wrong for your text, click it to switch between a capital start and lowercase. Click again to go back to the rule.
6. Use Copy or Save .txt. “Use as input” puts the result back in the text box, and Undo restores what was there before.

The twelve formats at a glance

Writing styles keep spaces and punctuation and change only the case of letters. The table shows the NASA guide to iPhone apps: what to know with “Keep acronyms and brand spellings” on; Title Case follows APA 7.

Programming styles split the text into words and join them with no spaces. The table shows user profile image URL. The acronym URL counts as one word, so it becomes Url.

Title case rules: APA 7 vs Chicago 18 (and EYD, RAE)

There is no single title case. The converter offers the four rule sets whose published wording was available to check: APA 7 and Chicago 18 for English, EYD V for Indonesian and RAE for Spanish. For English, the choice that matters is APA or Chicago.

The same titles give different results under the two English styles.

Line by line: with has four letters, so APA capitalizes it and Chicago 18 does not. From opens a subtitle after a colon, so both capitalize it. In line two, for is the last word; Chicago always capitalizes the last word, while APA lowercases a three-letter preposition there. In line three, if is on APA’s list of short conjunctions but not on Chicago’s list of lowercase conjunctions (and, but, for, or, nor), so Chicago capitalizes it. In line four, after and among are longer than four letters, so even Chicago 18 capitalizes them. Chicago changed this in its 18th edition: it now capitalizes prepositions of more than four letters, where earlier editions lowercased prepositions “regardless of length.” Older sources may therefore show Life after Death and Love among the Ruins.

Line five uses up as part of the phrasal verb back up, so it is an adverb, not a preposition. Chicago’s own Q&A capitalizes the up in “What Will Grandma Dress Up Like?” for the same reason. The converter treats up, down, out and off as adverbs and capitalizes them. If your title uses one as a real preposition, as in a walk up the hill, click the word in the strip to lowercase it.

MLA says to capitalize the first word, the last word and all principal words. The MLA Style Center page names no public list of the minor words that stay lowercase, and the AP Stylebook entry requires a login, so neither style is included. If your publisher requires MLA or AP, use the word check strip to adjust.

Acronyms, brands and proper nouns

Sentence case, Title Case and Capitalized Case lowercase everything after a word’s first letter, which would turn NASA into Nasa and iPhone into Iphone. With “Keep acronyms and brand spellings” on, the converter leaves alone any word that is already all capitals with two or more letters (NASA, HTML) and any word with a capital in the middle (iPhone, JavaScript, McDonald, O’Neil). In the word check strip these words get a dashed outline.

If most of the text is in capitals, there is no way to tell acronyms from ordinary words. The converter then lowercases them too and marks them “acronym unclear”; click a word to put the acronym back in capitals. It also cannot recognize proper nouns, so friday or seoul stay lowercase in Sentence case. Click them in the strip.

How code names are split

For programming styles the text is first split into words: at spaces, underscores, hyphens and periods; between a lowercase letter and a capital (userName becomes user and Name); and before the last capital of a run of capitals that is followed by lowercase (XMLHttpRequest becomes XML, Http, Request). Digits stay attached to the letters before them (html5Parser becomes html5 and Parser), and apostrophes are removed (don’t becomes dont).

The Google JavaScript Style Guide treats an acronym as an ordinary word: its own examples turn XML HTTP request into xmlHttpRequest (not XMLHTTPRequest) and new customer ID into newCustomerId. Line five matches the guide’s supportsIpv6OnIos example. Conventions differ by language and team, so here are the common references.

With Each line separately on, every line becomes its own name, so you can paste a list with one name per line and convert it all at once. With it off, all lines join into one name. If a result starts with a digit (2fa code becomes 2faCode), a notice appears under the word check strip, because most languages do not allow such variable names.

Excel, Google Sheets and Word

Spreadsheet functions are the quickest way to change a column of cells, and the Word menu is quickest for paragraphs. None of them has APA or Chicago title rules or programming formats. In a localized Excel the function names change: Microsoft’s Spanish help calls them MAYUSC, MINUSC and NOMPROPIO.

In Word, select the text and press Shift + F3 repeatedly to cycle between lowercase, UPPERCASE and Capitalize Each Word; Ctrl + Z undoes it. Excel’s PROPER, as Microsoft describes it, capitalizes the first letter of the text and any letter that follows a character other than a letter. That means a letter after an apostrophe is capitalized too, so =PROPER("it's o'neil's 2nd-hand shop") returns It'S O'Neil'S 2Nd-Hand Shop. This converter’s Capitalized Case leaves letters after an apostrophe or a digit lowercase and returns It's O'neil's 2nd-Hand Shop. For a name like O’Neil, type it as O’Neil in your text and “Keep acronyms and brand spellings” will leave it alone.

Common mistakes

• Using Capitalized Case where a title style is required: Word’s Capitalize Each Word and Excel’s PROPER capitalize every word, so you get A Guide To Cooking With Kids, with To capitalized. For a title that must follow APA or Chicago, use Title Case.
• Applying older Chicago habits: before the 18th edition, Chicago lowercased every preposition. Under the 18th, prepositions such as about, after and between start with a capital.
• Trusting Sentence case on ALL CAPS input: days, places, names and acronyms all become lowercase. Scan the word check strip and click each proper noun before you copy.
• Writing acronyms in code names as all capitals: XMLHTTPRequest hides where the words break. Google’s guide writes xmlHttpRequest instead.
• Expecting the length to stay the same: the German ß becomes SS in capitals. The ECMAScript specification notes that changing case can change the length of a string, so check the character count if a field has a limit.
• Starting a name with a digit: 2fa code becomes 2faCode, which most languages reject. Rename it, for example twoFactorCode.

Limits

• The converter does not identify parts of speech. Words on the lists are always lowercase, and up, down, out and off are always treated as adverbs and capitalized. For a different reading, click the word in the strip.
• It does not recognize proper nouns. “Keep acronyms and brand spellings” protects capitals you typed, but a name typed in all lowercase or all capitals follows the rule.
• A sentence ends at a period, question mark or exclamation mark followed by a space or line break. Abbreviations such as Mr., Dr., e.g., i.e., a.m. and p.m. are not treated as sentence ends, but an abbreviation not on the list can make the next word start with a capital. The first word after a line break is always treated as a sentence start, so text pasted from a PDF with lines broken mid-sentence gets a capital at the start of each line in Sentence case. Press those words in the strip, or remove the line breaks first.
• MLA and AP are not included: MLA Style Center confirms the first, last and principal words are capitalized but its list of minor words is not public, and the AP Stylebook entry requires a login.
• Hyphenated compounds are treated as separate words on either side of the hyphen with the same rule. Chicago’s extra rules for prefixes and similar compounds are not applied.
• Code names keep letters such as ü and é. Google’s JavaScript guide says to convert to plain ASCII first (Müller’s algorithm becomes Muellers algorithm), so edit your text beforehand if you need that. Characters without case, such as Korean, are joined as they are.
• Language-specific case rules, such as the Turkish dotted i, are not applied; the Unicode default is used.
• The result box marks changed letters in the first 4,000 characters, and card previews use the first 400. Copy and save always take the full text. Text files up to 2 MB are read as UTF-8.

Sources

Basis: style rules come from each publisher’s own page, program features from Microsoft and Google help, and naming rules from PEP 8 and the Google style guide, all checked on October 22, 2026. Your text is changed only in your browser and is never sent to a server.

• 01APA Style: Title case capitalizationArticles and conjunctions or prepositions of three letters or fewer stay lowercase; words of four letters or more are capitalized
• 02The Chicago Manual of Style Online: Q&A, Capitalization, TitlesFrom the 18th edition, prepositions of more than four letters are capitalized; the last word is always capitalized
• 03MLA Style Center: How should I capitalize the title of a handout?Capitalize the first word, the last word and all principal words (MLA Handbook 2.90)
• 04EYD Edisi V: Huruf KapitalRule 21: every word of a title starts with a capital except kata tugas not in first position
• 05RAE, Diccionario panhispánico de dudas: mayúsculas5.2.24: a work’s title capitalizes only its first word; capitals keep their accent marks
• 06Microsoft Support: PROPER functionCapitalizes the first letter and any letter that follows a character other than a letter
• 07Microsoft Support: UPPER functionConverts text to uppercase; the LOWER function has its own page
• 08Microsoft Support: Change the capitalization or case of textFive Change case options; SHIFT + F3 cycles lowercase, UPPERCASE and Capitalize Each Word
• 09Microsoft Soporte: Función MAYUSCThe Spanish-language name of UPPER; MINUSC and NOMPROPIO are the names of LOWER and PROPER
• 10Google Docs Editors Help: PROPERCapitalizes each word in a specified string
• 11PEP 8: Style Guide for Python CodeNaming Conventions: lowercase with underscores for functions and variables, CapWords for classes, capitals with underscores for constants
• 12Google JavaScript Style Guide6.3 Camel case: defined; UpperCamelCase classes, lowerCamelCase methods, CONSTANT_CASE constants
• 13Google Search Central: URL structure best practicesUse hyphens, not underscores, to separate words in URLs
• 14ECMAScript specification: String.prototype.toUpperCaseA case mapping can produce several code points, so the result may differ in length from the source

Frequently asked questions

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