Is realize or realized?

Realize and realise are alternate spellings of the same word. In the US and Canada, realize is by far the more common spelling. In the UK, Australia, and New Zealand realise dominates, though realize is sometimes used too. ... Realize and realise are two different spellings of the same word.

Is realize spelled with an s or AZ?

Yes, generations of readers and writers have grown up being used to reading realise with an s. But as either version is accepted there, and in America only one is, statistically the z wins. The Oxford University Press uses -ize endings in their style guide, but the Guardian does not.