American and British English spelling differences

American and British English spelling differences are one aspect of American and British English differences. In the early 18th century, English spelling was not standardised. Different standards became noticeable after the publishing of influential dictionaries. Current British English spellings follow, for the most part, those of Samuel Johnson's Dictionary of the English Language (1755). Many of the now characteristic American English spellings were introduced, although often not created, by Noah Webster (An American Dictionary of the English Language (1828)).

Webster was a strong proponent of spelling reform for reasons both philological and nationalistic. Many spelling changes proposed in the U.S. by Webster himself, and in the early 20th century by the Simplified Spelling Board, never caught on. Among the advocates of spelling reform in England, the influences of those who preferred the Norman (or Anglo-French) spellings of certain words proved decisive. Subsequent spelling adjustments in Britain had little effect on present-day U.S. spelling, and vice versa. While in many cases American English deviated in the 19th century from mainstream British spelling, on the other hand it has also often retained older forms.

The spelling systems of Commonwealth countries closely resemble the British system. In Canada, many "American" spellings are also used, often alongside "British" spellings. Detailed information on Canadian and Australian spelling is provided throughout the article.