Title Case Used For Interface Text
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Rule · bucket: judgment · severity: note · detector: none · since: v0.1.0
Section: UI writing
Group: Voice

Forbidden:
  "Add To Cart", "Save Post for Later?"

Instead:
  Sentence case: only the first word and proper nouns capitalised. "Add to cart", "Save post for later?"

Title case is harder to read — the eye expects lowercase, and each capital interrupts the scan. Its rules are also not standardised, so it is applied inconsistently even by people trying. Applies to headings, buttons, labels, menu items, table headers and dialog titles alike.