Unauthorised or unauthorized?
unauthorised is an adjective meaning “Alternative spelling of unauthorized”; unauthorized is an adjective meaning “Not having any authority”. Wiktionary gives them as spellings of the same word. In written English (wordfreq, 2021 data) unauthorized is about 3.6 times as common as unauthorised.
What is the difference between unauthorised and unauthorized?
| unauthorised | unauthorized | |
|---|---|---|
| Part of speech | adjective | adjective |
| Meaning | UKAlternative spelling of unauthorized | Not having any authority Without official authorization |
| Example | none recorded | none recorded |
| Pronunciation | not recorded | not recorded |
| In writing | 1.0 times per million words | 3.7 times per million words |
Sources: unauthorised and unauthorized in the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
Every current meaning of unauthorised and unauthorized
unauthorised
- 1
UKAlternative spelling of unauthorized
unauthorized
- 1
Not having any authority
- 2
Without official authorization
Source: the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); obsolete, archaic, dialect and rare senses left out.
Which is more common, unauthorised or unauthorized?
unauthorised appears 1.0 times per million words; unauthorized 3.7 times per million words.
unauthorised 1.0 times per million wordsunauthorized 3.7 times per million words
Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How many people search unauthorised vs unauthorized?
“unauthorised vs unauthorized” is searched about 10 times a month on Google and 10 on Bing in the United States. Google counts close variants of a query together (“unauthorized vs unauthorised”, “unauthorised or unauthorized”).
Sources: Google Ads keyword data through DataForSEO and Microsoft Advertising keyword data through DataForSEO, the average month from September 2025 to August 2026.