Unauthorised vs. Unauthorized — What's the Difference?

Unauthorised and unauthorized refer to actions, access, or operations that lack official permission or approval. The distinction between the two lies in their spelling, which corresponds to the differences between British and American English. "Unauthorised" is used in contexts following British English conventions, where the spelling retains the "s," a characteristic of many words in British English that end in "-ise." Conversely, "Unauthorized" is the preferred form in American English, which typically uses "z" in "-ize" endings.

Both terms are commonly used in legal, technological, and security contexts to indicate that something is not sanctioned by the rules, laws, or protocols of an organization, system, or legal authority. For example, "unauthorised access" in British English or "unauthorized access" in American English both refer to gaining entry to a system or information without permission.

The choice between "unauthorised" and "unauthorized" depends on the intended audience or the standard spelling practice of the publication, organization, or region. While international audiences can understand both spellings, using the variant consistent with the audience's norms enhances clarity and adherence to regional linguistic preferences.

Despite the spelling differences, the pronunciation of "unauthorised" and "unauthorized" is practically identical, with variations largely due to the accent and dialect of the speaker rather than the spelling.