Sentence case: Capitalize the first word of the text element, as well as any proper nouns.

Title case: Capitalize every word in the text, except:

  • Articles (a, an, the), unless they appear as the first word in a sentence
  • Coordinating conjunctions (and, or)
  • Prepositions, except the first or last word
  • Infinitives (to, in, an)

To check if you're using title case correctly, put your text into Capitalize My Title using the AP setting.



For desktop browsers, Android browsers, and websites:

Default to sentence case to support scanning and strike a friendlier, more human tone. We sentence case the following:

  • Headlines
  • Buttons

Unless otherwise stated in the word list, capitalize the following: brands and products (Mozilla, Firefox, Test Pilot, etc.) and acronyms (URL, etc.). Casing for features will depend on the feature (see the word list). We don’t capitalize features like “new tab,” “shortcuts,” or “passwords,” because they’re not proprietary.


While sentence case is the default, there are a few exceptions:



Global Operating System menu bar

Title case

Context menus within operating systems

Title case

Android snackbars

All caps (UNDO, DELETE)

Tab audio state


Brands and products

Title case proprietary names like Mozilla, Firefox, etc.


Title case


For the Firefox iOS browser:

Follow Apple's Human Interface Guidelines, which use headline-style capitalization. Capitalize every word except articles, coordinating conjunctions, and prepositions of four or fewer letters. Sentence case can be used for headlines written as a complete sentence with ending punctuation.

The following elements should always use title case: