What3words

Key takeaways

What3words belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect What3words to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of What3words from memory before moving on to harder problems.

Reference excerpt

What3words (stylized as what3words) is a proprietary geocode system designed to identify any location on the surface of Earth with a resolution of approximately 3 metres (9.8 ft). It is owned by What3words Limited, based in London, England. The system encodes geographic coordinates into three permanently fixed dictionary words. For example, the front door of 10 Downing Street in London is identified by ///slurs.this.shark. What3words differs from most location encoding systems in that it uses words rather than strings of numbers or letters, and the pattern of this mapping is not obvious; the algorithm mapping locations to words is copyrighted. What3words has been subject to a number of criticisms both for its closed source code and the significant risk of ambiguity and confusion in its three word addresses. This has led rescuers to advise against the use of What3words in safety critical applications. The company has a website, apps for iOS and Android, and an API for bidirectional conversion between What3words addresses and latitude–longitude coordinates.

History Founded by Chris Sheldrick, Jack Waley-Cohen, Mohan Ganesalingam and Michael Dent, What3words was launched in July 2013. Sheldrick and Ganesalingam conceived the idea when Sheldrick, working as an event organizer, struggled to get bands and equipment to the appropriate loading docks and entrances of large music venues. Sheldrick tried using GPS coordinates, but decided that words were better than numbers after transposing two digits led a driver to the wrong location. He credits a mathematician friend for the idea of dividing the world into 3-metre (10 ft) squares, and the linguist Jack Waley-Cohen with using memorable words. The company was incorporated in March 2013 and a patent application for the core technology filed in April 2013. In November 2013, What3words raised US$500,000 of seed funding. What3words originally sold "OneWord" addresses, which were stored in a database for a yearly fee, but this offering was discontinued as the company switched to a business-to-business model. In 2015, the company was targeting logistics companies, post offices, and couriers. In January 2018, Mercedes-Benz bought approximately 10% of the company and announced support for What3words in future versions of their infotainment and navigation system. In March 2021, it was announced that ITV plc had invested £2 million in What3words as the first investment in its media-for-equity scheme. What3words has raised more than £50m from investors since launching. In 2024, what3words had a turnover of £2.2m and made a loss of £10.6m.

Source of revenue The what3words system and app is free for anyone to use. The company states that its revenue comes from charging businesses that benefit from its products.

Design

Wordlists What3words divides the world into a grid of 57 trillion 3-by-3-metre (10 ft × 10 ft) squares, each of which has a three-word address. The company says it does its best to remove homophones and spelling variations; however, at least 32 pairs of English near-homophones still remain. Wordlists are available in 60 languages, each of which uses a list of 25,000 words (except for English, which uses 40,000 to cover sea as well as land). Translations are not direct, as direct translations to some languages could produce more than three words. Rather, territories are localised "considering linguistic sensitivities and nuances". Densely populated areas have strings of short words to aid more frequent usage; while less populated areas, such as the North Atlantic, use more complex words.

In a 2019 blog, open standards advocate and technology expert Terence Eden questioned the cultural neutrality of using words rather than the numbers generated by map coordinates. "Numbers are (mostly) culturally neutral," he said, "words are not. Is mile.crazy.shade a respectful name for a war memorial? How about tribes.hurt.stumpy for a temple?"

Ambiguity What3words state that similar addresses are spaced as far apart as possible to avoid confusion, and that similarly sounding codes have a 1 in 2.5 million chance of pointing to locations near each other. However, security researcher Andrew Tierney calculates that 75% of What3words addresses contain plural words that also exist in singular form (or the reverse). Co-founder and CEO Sheldrick responded that "Whilst the overwhelming proportion of similar-sounding three-word combinations will be so far apart that an error is obvious, there will still be cases where similar sounding word combinations are nearby." Further analysis by Tierney shows that in the London area, around 1 in 24 addresses will be confusable with another London address. In September 2022, the Department for Culture, Media and Sport used What3words to direct mourners to the end of the queue to view the Queen lying in state in London. Of the first five codes published, four led to the wrong place, including a suburb of London some 15 miles (24 km) from the real end of the queue. Officials later moved to an automated system to generate the identifiers, as they realised having people involved in the process resulted in typos. A paper published in 2023 investigated the patented algorithm without using What3words's own wordlist. It found that using linear congruence for address assignment does a poor job of randomising the wordlist. It also noted that the AutoSuggest feature did not return sufficient results to disambiguate an address. It concluded that "W3W should not be adopted as critical infrastructure without a thorough evaluation against a number of competing alternatives".

Reception According to Rory Sutherland from the advertising agency Ogilvy in a 2014 op-ed piece for The Spectator, the system's advantages are memorability, accuracy, and non-ambiguity in speech.

Mountain rescue Mountain rescue services in the UK have warned against relying on the app:

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with What3words

Start with the simplest possible case. Write down what What3words claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to What3words before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about What3words ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of What3words

In research: What3words appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses What3words in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: What3words is common in secondary-school and first-year university syllabi. It links to neighbouring topics Companies based in London, Geocodes, Internet properties established in 2013, so understanding it makes those chapters shorter.
In everyday life: Look for What3words outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study What3words in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what What3words means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain What3words out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is What3words in simple terms?

What3words (stylized as what3words) is a proprietary geocode system designed to identify any location on the surface of Earth with a resolution of approximately 3 metres (9.8 ft). It is owned by What3words Limited, based in London, England.

Why does What3words matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study What3words?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on What3words.