TL;DR, select text to convert only that part, or paste and click a case button for the whole block.
11 case formats, selection-aware conversion, Smart Title Case (AP/Chicago style), Preserve Acronyms, 30-step undo/redo, live all-formats preview, and drag-and-drop file upload. Live word and character counts. Nothing uploaded, nothing stored.
Free Online Case Converter – Change Text Case with Selection, Undo, and Smart Title Case
This free online text case converter goes well beyond the basic uppercase and lowercase buttons you find elsewhere. It converts any text to 11 case formats with a single click and adds advanced controls that make it genuinely useful for real editing and development work: selection-aware conversion so you can change one phrase without touching the rest of your document, Smart Title Case that follows AP and Chicago style guide rules, a Preserve Acronyms option that keeps HTML, API, and URL uppercase through any conversion, and a full 30-step undo/redo history.
A live all-formats preview panel lets you see your text in all 11 case formats at once before committing to one. Drag a .txt file directly onto the editor to load it instantly. Live counts for words, characters, characters without spaces, and sentences update as you type. Everything runs entirely in your browser — nothing is uploaded, nothing is stored.
What is text case conversion?
Text case conversion is the process of changing the capitalization pattern of letters in a string. Computers treat uppercase (A-Z) and lowercase (a-z) as completely different characters, so the same word written in different cases carries different meaning in file systems, programming languages, databases, and style guides.
Every professional field has settled on its own conventions. Writers use Title Case for headings and Sentence case for body copy. Developers use camelCase in JavaScript, snake_case in Python, kebab-case in CSS, and CONSTANT_CASE for environment variables. When content moves between teams, tools, or systems, a case converter eliminates hours of manual editing — and a selection-aware one eliminates the risk of accidentally converting text you did not intend to change.
Advanced features you won't find on other case converters
Most online case converters are simple one-shot tools: paste text, click a button, copy the result. This one is built as a real editing tool with power-user features designed for writers, developers, and content teams who work with large documents or complex naming conventions every day.
Selection-aware conversion
UniqueHighlight any word, sentence, or paragraph in the editor before clicking a case button. Only the selected text converts, and the rest of your document stays exactly as it is. A pulsing blue badge shows how many characters are selected and confirms that conversion will apply to the selection only. Click Clear selection to switch back to full-text mode. This is the feature that makes the tool genuinely useful for editing long documents: fix one heading or one variable name without touching anything around it.
Smart Title Case (AP and Chicago style)
AP/ChicagoStandard Title Case capitalizes every word. Published style guides like AP and Chicago specify that articles (
a, an, the), coordinating conjunctions (and, but, or, for), and short prepositions (in, on, at, to, by, of) should stay lowercase unless they are the first or last word. Toggle Smart Title Case in the Options bar to apply those rules automatically. The button label updates to Title Case (AP) so you always know which mode is active.Preserve Acronyms
DeveloperBy default, converting text to lowercase or Sentence case lowercases everything including acronyms like
API, HTML, URL, NASA, CSS, and JSON. Toggle Preserve Acronyms on and the converter detects any word that is 2 or more uppercase letters and keeps it unchanged during text conversions. This is essential for technical documentation, developer blogs, and product copy where acronyms carry specific meaning and must not be lowercased.Undo and redo history (30 levels)
Power userEvery case button click is saved as a separate step in a 30-conversion undo history. Click the undo arrow to step back one conversion at a time. Click redo to go forward again. If you want to jump all the way back to what you originally typed or pasted before any conversion, click Restore original for instant one-step recovery. Undo tracks button conversions only, so your native browser undo (Ctrl+Z) still works normally for individual keystrokes in the textarea.
Live all-formats preview panel
VisualClick Preview all formats to open a card grid that shows your text rendered in all 11 case formats simultaneously. When a selection is active, the cards show only the selected portion, so you can compare how a single phrase looks across every format before committing. Click any card to apply that format instantly. The card matching your current text format is highlighted, and developer-format cards are colour-coded in indigo to separate them from writing formats.
Drag-and-drop file loading
WorkflowDrag any
.txt file from your desktop directly onto the text editor. A full drop-zone overlay appears while you hover, and the file content loads the moment you release. The undo and restore stacks reset cleanly so you start fresh with the new content. This makes it easy to process files in a batch workflow without copy-pasting from a separate editor window.How to use this case converter
- Paste, type, or drop a file. Type or paste your text into the editor, or drag a
.txtfile onto the textarea to load it instantly. - Select a portion (optional). Highlight any word, sentence, or paragraph before clicking a button if you want to convert only that section. The blue badge confirms selection mode is on.
- Set options (optional). Enable Smart Title Case for AP-style capitalization rules, or turn on Preserve Acronyms to keep ALL-CAPS words unchanged.
- Click a case button. Or open Preview all formats to see all 11 outputs side by side, then click the card you want to apply.
- Copy or download the result. Use the Copy button or download as
.txt. If the result isn't right, click the undo arrow or Restore original to go back.
All 11 supported case formats
| Format | Example | Common uses |
|---|---|---|
| UPPERCASE | HELLO WORLD | Emphasis, labels, constants, acronyms |
| lowercase | hello world | Normalize CSV data, database fields |
| Sentence case | Hello world. | Body text, UI descriptions, subtitles |
| Title Case | Hello World | Page titles, headings, product names |
| camelCase | helloWorld | JavaScript/TypeScript variables, JSON keys |
| PascalCase | HelloWorld | React components, classes, interfaces |
| snake_case | hello_world | Python, Ruby, SQL column names |
| kebab-case | hello-world | CSS class names, URL slugs, HTML ids |
| CONSTANT_CASE | HELLO_WORLD | Env variables, config constants |
| aLtErNaTiNg | hElLo WoRlD | Memes, social posts, playful emphasis |
| iNVERSE | HELLO WORLD | Fix accidental Caps Lock, invert text |
Who uses a case converter and why
- Developers use it to refactor variable names between conventions, generate API field names, or normalize database column identifiers. The selection mode is especially useful for renaming one identifier inside a larger code snippet without converting everything else.
- Technical writers use Smart Title Case to produce AP-style headings without memorizing style guide rules, and Preserve Acronyms to keep product names like
REST APIorHTML5correctly formatted. - Content and SEO teams use Title Case and Sentence case for meta titles, H1 headings, and alt text, and use the live character counter to stay within Google's recommended limits.
- Data teams use lowercase conversion to normalize CSV column headers, form field names, and JSON keys before merging datasets or importing into a database.
- Designers and UX writers use it to standardize button labels, navigation items, and UI copy across a component library or design system — converting a batch of labels in the preview panel before deciding which format to apply.
Private and secure by design
This is a fully client-side text case converter. There are no server calls, no uploads, and no tracking of the text you enter. Your content stays in your browser tab and goes nowhere else. That makes it safe for source code, early drafts, internal naming decisions, and anything you would rather not send to a third-party server.
Frequently asked questions
What is a text case converter?
A text case converter changes the capitalization pattern of any text in one click. Instead of retyping letter by letter, you paste your text, choose a format like UPPERCASE, lowercase, or
camelCase, and the result appears instantly. This converter supports 11 formats and adds features like selection mode, Smart Title Case, acronym preservation, and undo history that most other tools do not offer.Can I convert only part of my text without changing the rest?
Yes. Select (highlight) any word, sentence, or paragraph in the editor before clicking a case button. Only the selected portion converts. The rest of your text stays exactly as it is. A blue pulsing badge shows the character count and confirms that selection mode is active. This is particularly useful for editing one heading in a long document or renaming a single variable in a code snippet.
What is Smart Title Case and how is it different from standard Title Case?
Standard Title Case capitalizes every word. Smart Title Case follows AP and Chicago style guide rules: articles (
a, an, the), coordinating conjunctions (and, but, or, for), and short prepositions (in, on, at, to, by, of) stay lowercase — unless they are the first or last word. Enable it in the Options bar and the Title Case button label updates to Title Case (AP) so you always know which mode is active.What does the Preserve Acronyms option do?
When enabled, any ALL-CAPS sequence in your text — like
API, HTML, URL, NASA, CSS, or JSON — is protected during text conversions. Without this option, converting to lowercase would turn The HTML API into the html api. With Preserve Acronyms on, those words stay uppercase while everything else converts normally. This setting applies to text cases only, not to developer formats like camelCase or snake_case where word boundaries change.Can I undo a case conversion?
Yes. Every case button click is recorded in a 30-step undo history. Click the undo arrow (↩) to step back one conversion at a time, and the redo arrow (↪) to go forward again. For a full reset, click Restore original to jump back to the text you first typed or pasted before any conversion. Note that undo tracks button conversions only — your browser's native Ctrl+Z still handles individual keystrokes normally.
Is there a way to see all case formats at once before applying one?
Yes. Click Preview all formats in the options bar to open a live card grid showing your text rendered in all 11 case formats simultaneously. When a selection is active, the cards preview only the selected portion. Click any card to apply that format instantly. The card for your current text format is highlighted, and developer-format cards are shown in indigo to help you navigate.
What is the difference between Title Case and Sentence case?
Title Case capitalizes the first letter of each major word. It is used for page headings, card titles, product names, and navigation items. Sentence case only capitalizes the first letter of each sentence, which suits body text, UI descriptions, and long-form content. For published content, use Smart Title Case to follow AP or Chicago style guide rules automatically.
What is the difference between camelCase and snake_case?
camelCase joins words by capitalizing each word after the first — for example getUserProfile. It is standard for JavaScript variables, TypeScript functions, and JSON keys. snake_case uses underscores between lowercase words — for example get_user_profile — and is common in Python, Ruby, and database column names. Both are supported, and the converter handles mixed inputs like get-user-profile-data or getUserProfileData cleanly.What is PascalCase and when should I use it?
PascalCase capitalizes the first letter of every word including the very first — for example
UserProfileCard. It is the convention for React component names, TypeScript interfaces, C# classes, and most object-oriented class names across languages. PascalCase is sometimes called UpperCamelCase.What is CONSTANT_CASE used for?
CONSTANT_CASE (sometimes called SCREAMING_SNAKE_CASE) uses all uppercase letters with underscores between words — for example
MAX_RETRY_COUNT. It is the convention for environment variables, configuration constants, and global settings in JavaScript, Python, Go, and most other languages. It visually signals that the value should not be changed at runtime.How do I convert text to kebab-case for CSS class names or URL slugs?
Paste your text and click kebab-case. The converter lowercases all letters and replaces spaces, underscores, and camelCase boundaries with hyphens — giving you
my-css-class-name. Use this format for CSS class names, HTML id attributes, URL slugs, GitHub repo names, and NPM package names.How do I change all caps to lowercase online?
Paste your ALL CAPS text into the editor and click lowercase. Every letter converts instantly. If your text contains acronyms you want to keep uppercase (like API or HTML), enable Preserve Acronyms in the Options bar first.
Can I use this to rename variables between coding conventions?
Yes. The converter parses mixed input by splitting on spaces, underscores, hyphens, and camelCase boundaries before rebuilding in your target format. Text like
getUserProfileData or get-user-profile_data both convert cleanly to any of the 11 supported formats. Pair this with the Find & Replace tool to do bulk renames across a block of code.Does the converter change numbers or punctuation?
No. Only letters are affected. Numbers, punctuation marks, emoji, and symbols are preserved exactly as typed — including when you convert to developer formats like snake_case or kebab-case.
Is my text sent to a server or stored anywhere?
No. The entire tool runs locally in your browser tab. Nothing you type, paste, or drop is ever sent to a server, logged, or stored outside your device. This makes it safe for source code, early drafts, internal documents, and anything else you want to keep private.
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