Oxford spelling (also Oxford English Dictionary spelling, Oxford style, or Oxford English spelling) is a spelling standard, named after its use by the Oxford University Press, that prescribes the use of British spelling in combination with the suffix -ize in words like realize and organization instead of -ise endings.
Oxford spelling is used by many UK-based academic journals (for example, Nature) and many international organizations (for example, the United Nations and its agencies).[1][2][3] It is common for academic, formal, and technical writing for an international readership. In digital documents, Oxford spelling may be indicated by the IETF language tag en-GB-oxendict (or historically by en-GB-oed).[4]
[W]e use Oxford English spelling. So, for all of you wondering why we put 'z's in lots of words that you don't think we should, hopefully that answers your question.
Where there is a choice between using the suffix -ize or -ise (e.g. organize or organise), -ize, derived from the Greek ‑izo, is preferred, consistent with the first spelling of such words given in The concise Oxford dictionary [sic].