The free What3Words app is increasingly being used by emergency services to help quickly locate and coordinate rescues, particularly in the UK - but it's not infallible. Here's everything you need to know on how to use it and what to be aware of.


Police and the East Anglian Air Ambulance conducted a dramatic rescue of an injured mountain biker from Thetford Forest, using location app What3Words to pinpoint his location.

The 59 year old rider, identified only as Keith, was riding with friends when he lost control and crashed badly, severely injuring himself. Luckily, police officers fortuitously driving an off-road vehicle nearby found the group, and called for help using the What3Words app to pinpoint their location. Since Thetford Forest is one of the largest forests in the UK, this helped save time and allowed the air ambulance to reach him quickly.

Keith was flown to Addenbrookes Hospital where he received treatment for multiple fractures, a punctured lung and damaged spleen, spending four days in the ICU then seven days on the ward, and went on to make a full recovery.

“Without the use of what3words we would have really struggled to let the emergency services know where we were and the rescue would have taken a lot longer”, commented Neil afterwards. “I do think that if we didn’t use the app, I could have had a totally different outcome because of the time it would have taken to locate us”.

What is What3Words

What3Words is a privately owned, proprietary geocode system.

A geocode – or geographic code – is a code that symbolises or represents a specific geographic location or object. The geocode system most people are familiar with are map coordinates which is a numerical system based off latitude and longitude measurements.

What3Words divides the surface of the Earth into a grid of three squared metres, based on GPS (Global Positioning System) coordinates, and which uses a word-based system to identify each grid location rather than a numerical system. The result is that locations can be identified using a sequence of three words, the idea being that these are easier to communicate than long strings of numbers, and are ‘as accurate GPS coordinates‘.

From a user perspective, What3Words is a downloadable mapping app. When you open it, it’s a little like any other mapping software with a base map viewable as a simple representation or as a satellite view. You can use the app to identify the What3Words code for a specific location by either touching the location on the map, putting in an address, or using the automatic positioning system to identify where you are.

The app has a voice system so you can simply speak the What3Words address you are looking for, and you can also use the app for navigation.

It is currently used by around 85% of emergency services in the UK, according to What3Words, though it is unclear whether this is a geographic spread. In the UK it is used by many police, ambulance and fire and rescue services, as well as the coastguard, and, according to What3Words, has ‘become an important part of the emergency toolkit for response teams country-wide.’

What3Words is available in 50 languages, and uses a list of approximately 25,000 words to produce the requisite number of combinations. However, the English language version uses considerably more – up to 40,000 – as it covers the sea as well as land.

Do I need phone signal to use What3Words

Provided you’ve already downloaded the app, you don’t need phone or wifi signal to generate a What3Words code for your location since it uses GPS, although you may not be able to load or view the base map. So provided those words are correct, you can share them with emergency services.

That does raise the issue that it might not be possible to check whether the 3-word code that is generated does in fact correspond with your location if you can’t check it against a map.

And of course, if you do need to call the emergency services, you will need phone signal. Therefore, ideally if you are heading somewhere where you may have limited service or coverage, it’s always a good idea to have an alternative method of seeking help should you need it.

How to use What3Words in an emergency

What3Words recommend the following actions to use the app in an emergency situation. Please note that, as mentioned above, while the app doesn’t need wifi/phone signal to provide a location code, you will need some kind of signal to call the emergency services.

If you already have What3Words downloaded to your phone:

  1. Ensure you’ve already downloaded the What3Words app to your phone. It is available for both Android and iOS, and is free.
  2. Open the app and click the blue arrow (iOS) or compass (Android) to find the What3Words code for your location. What3Words recommends waiting for a few seconds if the blue location dot is moving about, to allow it to stop moving which will provide the most accurate result.
  3. If you are calling emergency services, clearly share the What3Words code with the call handler. Be careful about pronunciation and plural/singular terms, and add any additional detail you can provide about the location including landmarks such as roads, towns, rivers, etc.

If you don’t have What3Words downloaded on your mobile phone:

  1. The emergency services call handler may send you an SMS text message with a link to open What3Words on your internet browser.
  2. The page will show your What3Words location code, and the GPS of your device’s accuracy in metres. Click refresh to refine that accuracy.
  3. Share the What3Words code with the call handler plus any other additional details you can provide about the location including landmarks such as roads, towns, rivers etc.

Note: not every emergency service will accept What3Words, so to reiterate, it’s very important to supply as much additional location information as you can.

Potential issues with What3Words

When you’re dealing with such a vast area and a system that relies on an algorithm, errors and issues are bound to creep into the mix. Algorithms are created by humans, albeit very skilled ones, so human error, bias and omission can sneak in there; though one would hope that with continued refinement, these errors can hopefully be identified, rectified or reduced.

And of course the system itself is used by humans, often out in difficult, stressful situations, and then relayed through a series of other systems and people, where more errors can crop up.

Some of main issues, as reported on an article on the BBC News website as being identified by security expert Andrew Tierney, and other issues, include;

Similar sounding words

The English language is full of homophones – words that sound the same when spoken, but are spelt differently. In a system that relies on verbally relaying a sequence of words, this can be a massive problem. For example, wring and ring, rode and road, flower and flour.

What3Words states on its website that ‘when we select the words to be used in each language, we do our best to remove homophones and spelling variations’.

Singular and plural words

What3Words uses both singular and plural versions of a word; for example, flower and flowers, boat and boats. A simple mistake in which the wrong version is communicated could mean sending an incorrect location to emergency services.

Similar words in close proximity

One way of mitigating the above issues is to ensure that any What3Words locations that the above issues could apply to aren’t near each other, and by ideally providing a little additional information. That way, should someone state words that reveal a location of, say, the Scottish Highlands but they’ve just said they’re walking up Snowdon in Wales, it will be clear the What3Words code provided is incorrect.

However, Tierney identified in an article on the BBC dated June 2021, that on a significant number of occasions, two easily confused word sequences have referred to locations in a similar geographic area. For example, this could mean two opposite sides of the same mountain. This could mean emergency services waste precious time going to the wrong location.

What3Words state that ‘Our algorithm shuffles what3words addresses, which means similar word combinations were placed far apart. For example, ///table.chair.lamp is located in New South Wales, Australia, whereas ///tables.chair.lamp is in Minnesota, USA. The overwhelming proportion of similar 3 word combinations are so far apart that an error is obvious. We also worked hard to remove homophones and near homophones like sale and sail.’

The app also has an autosuggest feature that lists alternative similar combinations of words to the ones being inputted, as well as the location distance from the user, to help the user spot if they words they have are for the wrong location.

However, the company do recognise that potentially confusing combinations can still occur, which is why it states that the app is part of a toolkit rather than a stand-alone solution, and that emergency service call handlers will likely ask for additional information rather than relying on What3Words alone.

Global spread

The flip side of the above is that if the incorrect sequence of words are used, the code could be for literally anywhere on the planet, and this is something some emergency services have reported happening in a BBC News article.

While it should hopefully rule out the location as incorrect immediately, it could potentially cause delays if communication with the person making the emergency call is not direct and consistent, as the service provider would need to reconnect via the call handler to check location information.

Pronunciation and spelling

Imagine being caught in an emergency situation on a mountain side. Your friend is injured and in pain, and you’re helping them. The wind and rain is picking up and it’s noisy. Your hands are getting cold. All of this can hamper how clearly you can relay those three words to emergency services, either verbally on a call or via text message, and a typo or noisy environment can mean the difference between sharing your location accurately and not.

And there are potentially other issues; if the person has an accent or stammer, if they’re slurring their words, if they have dyslexia – all of these have the potential to affect the accuracy of information conveyed.

Proprietary system

The system is also proprietary, meaning that the company What3Words owns the algorithm and data, and it is not open source. While it grants free access to emergency services, it also means that impartial and transparent evaluation of the algorithm technology, which is copyright protected, is unlikely.

GPS accuracy

While it can work without wifi or phone signal connection, What3Words still relies on GPS for location, and accuracy will depend on the strength of the GPS signal as well as the receiver. According to the US Gov GPS website, ‘GPS-enabled smartphones are typically accurate to within a 4.9 m (16 ft.) radius under open sky. However, their accuracy worsens near buildings, bridges, and trees.’

Weather conditions can also affect accuracy, as can satellite position.

Alternatives to What3Words

While What3Words can be helpful, provided it’s used correctly, as the company itself suggests in an emergency situation it is best used as part of a toolkit rather than being relied on completely for navigation and location pinpointing. We’d always recommend ideally having another primary way of sharing your location in case you need help.

The first and best way is to let someone know where you’re going in the first place and when you’re likely to be back. By sharing your route and return time, if you don’t make an appearance when you’re supposed to and can’t be contacted, it’s much easier for rescuers to narrow down where you might be.

The second is to bring and use an old-fashioned paper map if you’re heading out into the hills. While they might be bulky and awkward, they don’t rely on wifi or GPS signal for locating yourself or navigating yourself somewhere safe. Maps can frequently be bought from local shops and bike shops as well as online, and there are plenty of guides online if you need to brush up on your map reading skills, such as the simple ‘How to read a map’ guides on the Ordnance Survey site in the UK.

To make this even simpler, the Ordnance Survey in the UK have the OS Locate app. Used in conjunction with the OS Maps app, it works in a similar way to What3Words in that is has the ability to determine your location without wifi or network signal, producing a set of GPS coordinates as well as a digital compass to help you work out directions. However some of the same issues appear here; to call emergency services you will still need signal, and the coordinates need to be clearly communicated to share the accurate location.

Other options are things like emergency beacons, which are increasingly being built into technology and accessories, such as Apple Watch crash detection and the ANGi crash sensor on Specialized Helmets. These will detect a user crash, and can be pre-set to inform an allocated contact, including location information.