Case Converter

Each language and platform has its own conventions

Which case to use isn't a matter of taste; it's about following the conventions of an ecosystem. Violating them might not break your code, but you'll get flagged in code reviews and run into friction with autocomplete and linters.

The most common task: converting between API responses and code

In practice, you'll probably open this tool for a few specific reasons. A Python or PHP backend is sending `snake_case` JSON, but your frontend uses `camelCase`. Or you need to turn a list of database columns into JavaScript object keys.

Just paste your text into the input, and all 14 formats will appear instantly. Copy the one you need. Note that the tool treats the entire input as a single string to split into words—line breaks also act as word separators. If you paste multiple lines, they'll be merged into a single `camelCase` string. The intended use is to convert one line at a time.

• It works in reverse, too. Paste in `camelCase`, and it will split the words at the capital letters to create `snake_case`. Check the word count to the right of the input box to see how many words it recognized.
• `dot.case` is for config file keys (like `spring.datasource.url`) or logging namespaces. `path/case` is useful for building URL paths.
• The Reverse function works on code points, so it won't break multi-byte characters like emoji or Korean.

What happens with acronyms?

This is a genuine point of debate among developers. How should `HTTPServer` be split? This tool's rule is to split a word when a sequence of uppercase letters is followed by an uppercase letter and then a lowercase one. It recognizes `HTTPServer` as `HTTP` + `Server`, and `XMLHttpRequest` as `XML` + `Http` + `Request`. This results in a `snake_case` of `http_server` and `camelCase` of `httpServer`.

The results might not always be what you expect. `userID` correctly splits into `user` + `ID` to become `user_id`, but names with consecutive capitals can be split differently than a human would intend. For names with many acronyms, it's best to visually check the results.

What happens when Korean text is included?

Korean characters (Hangeul) don't have uppercase or lowercase. Applying case conversion leaves them unchanged. For this reason, the tool preserves Korean text as-is—converting "상품 재고 관리" to camelCase results in "상품재고관리".

If Korean and English characters are joined, the tool treats the boundary as a word break. "사용자Name" is recognized as two words, `사용자` + `Name`, which becomes `사용자_name` in snake_case. You might encounter this pattern in the wild.

• As an intermediate step when converting Korean item names from a planning document into English variable names, you can first clean up the separators.
• When creating temporary keys from Korean column headers received in an Excel file. However, avoid leaving Korean identifiers in your final code, as encoding issues can cause them to break in different tools and environments.
• While browsers can handle Korean characters in CSS classes or URL paths, they get percent-encoded, making URLs long and unreadable. Some build tools may also fail to process them.

What this tool doesn't do

The tool only applies mechanical rules and doesn't understand context. Here are its limitations, stated plainly.

• `Title Case` capitalizes the first letter of every word. Proper English title capitalization would keep articles and prepositions (like 'a', 'the', 'of', 'in') lowercase, but this tool doesn't make that distinction. You'll need to manually edit the result for a formal English title.
• `Sentence case` assumes a new sentence begins after a period, exclamation mark, or question mark. It will mistakenly capitalize the word after a period in an abbreviation, like in "Dr. Kim".
• All formats other than `UPPERCASE`, `lowercase`, and `Sentence case` discard the original punctuation (as it's used only as a delimiter). If you want to preserve your original sentence structure and punctuation while changing the case, use the `UPPERCASE`, `lowercase`, or `Sentence case` fields.