Optimize vs. Optimise: Which Spelling is More Formal?

Both 'optimize' and 'optimise' are correct spellings of the word. 'Optimize' is the American English spelling, while 'optimise' is the British English spelling. Therefore, 'optimize' is considered more formal in countries like the United States and Canada. In the United Kingdom, Australia, and other countries that use British English, 'optimise' is considered the more formal spelling.