The four everyday cases, and the rule for each
Most case tasks are one of four styles. The two that get confused are title case and sentence case: one capitalizes every important word, the other only the first.
| Case | Rule | Result |
|---|---|---|
| UPPERCASE | Every letter capital | THE QUICK BROWN FOX |
| lowercase | Every letter small | the quick brown fox |
| Title Case | First letter of each word capital | The Quick Brown Fox |
| Sentence case | First letter of the sentence capital | The quick brown fox |
Strict title case also lowercases short words such as "a", "of" and "the" when they fall inside the line; a plain converter capitalizes every word instead.
Programming cases join the words together
Code identifiers cannot hold spaces, so each style encodes the word breaks in its own way. Pick the one your language expects.
| Case | Example | Common use |
|---|---|---|
| camelCase | quickBrownFox | JavaScript, Java variables |
| PascalCase | QuickBrownFox | Class and type names |
| snake_case | quick_brown_fox | Python, SQL columns |
| kebab-case | quick-brown-fox | URLs, CSS, file names |
| CONSTANT_CASE | QUICK_BROWN_FOX | Constants, env variables |
Two things that break a naive converter
- Letters only — digits, punctuation and symbols never change. "Order #12A" lowercases to "order #12a", touching just the letters.
- Some letters aren't one-to-one — the German ß uppercases to "SS", so the text gets one character longer. Turkish dotted and dotless i also swap differently from English, which is why locale can matter.
Common questions
What is the difference between title case and sentence case?
Title case capitalizes the first letter of every significant word, the way a headline reads. Sentence case capitalizes only the first word (and any proper nouns), the way an ordinary sentence reads.
Does changing case affect numbers and symbols?
No. Case only applies to letters, so digits, spaces and punctuation pass through unchanged. Only A to Z and their accented equivalents flip.
Can I undo a case change?
Not reliably. Going to all lowercase throws away which letters were capitalized, so you cannot recover the original from the result. Keep a copy of the source text if you might need it back.
