100% free · Runs 100% in your browser · Fixed dictionary of unambiguous pairs only · No signup needed
Deliberately left untouched: ambiguous, context-dependent words are NOT converted, because guessing would be wrong — programme/program, practise/practice, licence/license, grey/gray (also a name), and cheque/check. This converter uses a fixed dictionary of unambiguous pairs only, so some words in your text may legitimately stay unchanged.
English is spoken on both sides of the Atlantic, but it is not spelled the same way on both sides. British English writes colour, favourite, and organise, while American English writes color, favorite, and organize. The differences are systematic, not random: they follow patterns that go back centuries, and once you know the patterns, most conversions feel predictable. Even so, converting a long document by hand is slow and error-prone, because it is easy to miss a word or to change one that should have been left alone.
Our free UK-US Spelling Converter does that job for you in your browser. Paste your text, choose a direction, either UK to US or US to UK, and the tool converts the spelling throughout your document. It shows you a live replacement count, highlights the changed words in the preview so you can review every edit, and lets you copy or download the result. There is no sign-up, nothing to install, and your text never leaves your device.
Most UK-US differences fall into a handful of recognisable patterns. Words ending in our in British English usually end in or in American English, as in colour and color, favour and favor, honour and honor. Words ending in re in British English often end in er in American English, as in centre and center, theatre and theater. The ise ending in words like organise and realise becomes ize in American English, giving organize and realize, and double consonants differ too: British travelling becomes American traveling, and British labelled becomes American labeled.
Other differences are word-by-word rather than pattern-based. The British noun licence is spelled license in American English for both noun and verb, and the British programme for a television schedule is program in American English, though program is also the spelling for computer programs in both varieties. Knowing these patterns helps you understand what the converter is doing, but you do not need to memorise them: the tool applies them for you, consistently, across the whole document, without missing a single instance.
No automatic converter can be right about every word, and an honest one says so. Some words are context-dependent, meaning the correct conversion depends on what the word means in that particular sentence, not just on how it is spelled. Programme versus program is the classic example: a television programme in British English becomes a program in American English, but a computer program is spelled program in both varieties, so blindly converting every programme would create errors. The same applies to practise versus practice and to grey versus gray when grey is part of a name.
That is why this converter uses a fixed dictionary of unambiguous pairs only, and deliberately leaves ambiguous words untouched rather than guessing. It lists the ambiguous words it leaves alone, so you can review them yourself and decide case by case. A tool that guesses on ambiguous words might look more thorough at first glance, but it would quietly introduce mistakes into your text. Leaving a handful of words for human judgement is the safer, more honest trade, and it keeps your document accurate rather than merely changed.
Spelling conversion must respect capitalisation, or it will damage your text in a different way. This converter preserves case: Colour at the start of a sentence becomes Color, not color, and a word written entirely in capitals stays entirely in capitals. Headings, titles, and acronyms therefore survive conversion intact, and you do not need to go back through the document fixing capital letters that a careless tool broke. It is a small detail, but it is the difference between a result you can use immediately and one that needs another round of proofreading.
The highlighted preview is the feature to use first after every conversion. Skim through the highlighted words and confirm each one looks right in context. That quick review takes less than a minute for most documents and catches the rare case where a word you expected to stay unchanged was converted, or where an ambiguous word you wanted changed needs a manual edit.
For long documents, convert in sections if you prefer to review as you go, or convert the whole document at once and then work through the highlights from top to bottom. Either way works, because the replacement count and highlighting give you a complete record of what changed.
Students submitting work to a university that expects one spelling convention, authors preparing a manuscript for a publisher in another country, and businesses writing for customers on the other side of the Atlantic all run into this problem regularly. A British company selling into the United States wants its website to read naturally to American visitors, and an American writer contributing to a British publication wants the reverse. In both cases, consistent spelling signals professionalism and attention to detail, while mixed spelling looks careless even when the content itself is excellent.
Bloggers and content creators benefit too. If your audience is mainly in one country, matching its spelling convention makes your writing feel local rather than imported, which builds trust with readers. After converting, you can polish the result further with related tools on this site, such as the Article Rewriter, the AI Paraphraser, the Readability Checker, or the Blog Title Generator for your next headline.
Well-edited writing deserves a professional home on the web. FistHost shared hosting starts from just $0.99 per month, giving you an affordable way to launch a blog, a business site, or an author portfolio where your carefully polished content can reach readers in any country. With a free domain included with an annual plan, you can set up your site without a large upfront cost and start publishing right away. Explore the plans at FistHost and pick the one that fits your project.
Your own domain also means your writing lives somewhere you control, in the spelling and style you chose, rather than inside a social platform that can change its rules at any time. That permanence matters for writers building an audience over years, not days. FistHost hosting is built for that kind of steady publishing: quick setup, dependable uptime, and support when you need it. Visit FistHost to get your site online today.
The most common mistake is converting only part of a document, leaving a mix of British and American spellings that looks worse than either convention on its own. Always convert the whole document, then review the highlights. Another common mistake is forgetting about proper nouns: place names, company names, and titles should usually keep their original spelling, and you should check the highlighted preview for any name that was changed and restore it manually if needed. Finally, remember that spelling is only one part of localisation. Vocabulary differs too, and this converter changes spelling only, not word choice, so a document converted from British to American English will still read as British in its vocabulary unless you edit that separately.
Does it convert every word? It converts the unambiguous pairs in its fixed dictionary. Ambiguous, context-dependent words are deliberately left untouched and listed for your review, rather than guessed at.
Does it preserve capitalisation? Yes. Colour becomes Color at the start of a sentence, and all-caps words stay all-caps.
Does it change vocabulary? No. It changes spelling only, not word choice, so words like flat and apartment are not swapped.
Is my text uploaded? No. The converter runs entirely in your browser and your text never leaves your device.
Spelling conventions are a small detail with a large effect on how professional your writing looks to its intended audience. This free converter applies the systematic UK-US patterns consistently, preserves your capitalisation, highlights every change for review, and honestly leaves the ambiguous cases to your judgement. Paste your text, pick a direction, and get a cleanly converted document in seconds.
No reviews yet. Be the first to review this tool!
Reviews are protected by captcha and moderated before they appear.