UK vs US Spelling Checker

How British and American spelling differ, and how this tool decides

The two varieties differ in a few regular ways. -our / -or: colour, favour, honour, neighbour (US color, favor, honor, neighbor). -re / -er: centre, litre, theatre (US center, liter, theater). -ise / -ize: British writing uses both; most publishers choose -ise, while Oxford University Press house style (Oxford spelling) uses -ize but keeps -yse (analyse, paralyse), so analyze is American in every British style. Doubled l: travelling, cancelled, labelled (US traveling, canceled, labeled). -ence / -ense: defence, offence, licence as a noun. ae / oe: paediatric, anaemia, oestrogen (US pediatric, anemia, estrogen). And a set of single words: tyre, kerb, grey, aluminium, pyjamas, cheque, jewellery, mould, plough.

Words that change with the meaning. Some spellings are correct in both varieties depending on how the word is used, so the tool looks at the words around them instead of flagging every one:

• practice / practise. In British English practice is the noun (in practice, a medical practice) and practise the verb (to practise the piano). American English uses practice for both. In British mode, practice is flagged only after words such as to, will, can or we; practising and practised are always British.
• licence / license. Noun licence, verb license in British English; American English uses license for both. License after a, the, driving and similar words is marked as a probable noun; after to or will it is left alone.
• program / programme. Both varieties write program for computer programs. British English writes programme for a television or radio show, a course or a plan. Program is left alone when computing words are nearby, and otherwise marked low.
• tyre, kerb, cheque, metre, dialogue. Tire is also a verb, curb also means to restrain, check also means to verify, meter is also a measuring device and dialog is normal in computing (a dialog box), so these American forms are flagged only when the context points to the British meaning.
• Words that are the same in both. advise, comprise, exercise, promise, revise, size, prize, seize, analyses (the noun plural), draft, story, inquire and many more are never flagged, because they are not different.

What the tool leaves alone. Links, e-mail addresses and text between backticks are skipped. Capitalised words in the middle of a sentence are skipped by default, since they are usually names. Where British English accepts both spellings (for example fetus and foetus, sulfur and sulphur in science writing, encyclopedia, inquire, toward), only the direction that is clearly needed is flagged: it will not tell you that a common British spelling is wrong. Text in other languages is not checked. For the other kinds of regional difference use the Date Format Converter (day/month order) and the Oven Temperature Converter; for word counts try the Keyword Density Checker.

Source / Last verified (26 September 2026): the word lists are our own, written from the well-known patterns described above. No dictionary or third-party list was copied, and no dictionary was consulted while building them, so they have not been checked against a published source. Pairs where British usage varies are marked medium or low. When you are unsure about a word, look it up in a dictionary such as the Oxford English Dictionary or Collins English Dictionary. The list is small compared with a dictionary and will not catch every difference.