UK ↔ US English Spelling Converter
Convert between British and American English spelling instantly — no sign-up required.
About this tool
This free converter handles over 150 common spelling differences between British and American English, plus automatic suffix pattern matching for thousands more words. It covers the most frequent categories: -our / -or (colour, honour, favour), -re / -er (centre, theatre, fibre), -ise / -ize (organise, realise, specialise), -ogue / -og (catalogue, dialogue), and double-L patterns (travelling, cancelled, jewellery).
Text inside code blocks, URLs, and hyphenated compound words is left untouched. Original capitalisation is always preserved — all-caps, title case, and lowercase words are each handled correctly.
Common UK ↔ US spelling differences
-our → -or
-re → -er
-ise → -ize
-ogue → -og
Double-L patterns
Other differences
Frequently asked questions
What is the difference between British and American English spelling?
British and American English diverged during the 18th and 19th centuries. Noah Webster's 1828 dictionary standardised many American spellings, simplifying patterns like colour → color and centre → center. Today there are several hundred consistent differences, mostly in word endings and certain letter substitutions.
Does this tool handle inflected forms like "organised" or "travelling"?
Yes. The converter matches inflected forms including past tense (-ised/-ized), present participle (-ising/-izing), agent nouns (-iser/-izer), and nominalisations (-isation/-ization), so "organising", "organised", "organiser", and "organisation" are all handled correctly.
Will it change words like "advertise" or "surprise"?
No. Words ending in -ise that are not UK/US spelling variants — such as advertise, surprise, revise, advise, enterprise, and franchise — are explicitly excluded and left unchanged.
Are code snippets and URLs preserved?
Yes. Text inside backtick code blocks, inline code, URLs, and hyphenated compound words (e.g. well-organised) are detected before conversion and restored unchanged afterwards.
Is this tool free and does it store my text?
The tool is completely free to use with no sign-up required. Text is sent to our server only to perform the conversion and is not stored or logged.