How to Use This Tool
Paste your text and pick a target. The conversion runs in both directions — it does not matter which variety you started in.
−ize is not American
This is the assumption that breaks most converters. The -ize ending comes from the Greek -izein and is the older English form. Oxford University Press uses it in British English, and always has. Cambridge, the Guardian and most other UK publishers use -ise.
So organize is correct British English in one house style and wrong in another, and calling it “the American spelling” is simply inaccurate. That is why this tool offers Oxford as its own target: British with -ise and British with -ize are different answers, and you need to know which your publisher wants.
The verbs that are never −ize
Roughly twenty verbs end in -ise because of their Latin or French roots, not because of the Greek suffix. They are spelled -ise in Britain, in America, in Oxford style, everywhere:
advertise · advise · arise · chastise · comprise ·
compromise · despise · devise · disguise · excise · exercise ·
franchise · improvise · incise · merchandise · promise · revise
· supervise · surprise · televise
A converter that swaps every -ise produces advertize and surprize. Those are not American spellings; they are not spellings at all. The output looks deliberate, which makes it harder to spot than a typo.
The explicit list is not enough on its own, either. Wise, rise, noise, praise, paradise, precise and otherwise all end in those three letters without being verbs at all. So three further tests run before any substitution: a word ending in -wise is left alone because that is always the adverb suffix, a vowel immediately before the -ise means it belongs to the root, and a stem shorter than four letters cannot be a suffixed verb.
The pairs no tool can resolve
Two families differ by part of speech in British English and not at all in American:
- licence / license. British: licence is the noun, license is the verb. American: license for both.
- practice / practise. British: practice is the noun, practise is the verb. American: practice for both.
Converting American to British therefore requires knowing whether license in your sentence is a thing or an action, and no word list can tell. This tool marks those words instead of guessing, because a wrong guess here is a grammatical error rather than a spelling variant.
Programme is a third case with a twist: British uses programme for a broadcast or a schedule but program for computer software, following American usage. The tool converts it and flags it, since the right answer depends on what you are writing about.
What is covered
The common families: -our/-or, -re/-er, -ise/-ize, -yse/-yze, -ce/-se, doubled consonants before a suffix (travelling, modelled), and ae/oe reductions (anaemia, oesophagus). Capitalisation is preserved, so a word at the start of a sentence stays capitalised.
It is a word list, not a dictionary. Rare words and proper nouns pass through untouched, which is the safe direction to fail in.
