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what3words (what3words.com) is a service that assigns a location reference comprised of 3 words to a 3m x 3m grid square. As such, what3words is not an addressing system: it does not hand out addresses to individual entities, rather it just encodes coordinates in a textual way.

Non-open patented location reference scheme

what3words is very much not an open system for location reference/addressing. There are several levels of non-openness:

  • The algorithm/idea is patented, very actively preventing anyone from implementing a compatible algorithm or developing anything like it as a competing standard (although the validity of this patent is questionable given the existence of what would seem to be prior art on the idea)
  • Hand-in-hand with this patent, the software for encoding/decoding is copyrighted. Any software you can find or reverse engineer from the website or mobile apps, could not be copied and re-used legally. what3words have actively served github with a DMCA takedown notice to remove some reverse-engineered code.
  • The scheme also requires a database look-up to some extent. The encoding/decoding is partially algorithmic (It doesn't use a database of every three word location code) however it does require a database. The database is (at least) a dictionary of words, plus some information on regions to apply different languages, plus some information on ocean regions where the system uses longer words. The database is shipped with apps for offline use, and is copyright what3words. For online use the need for database look-ups creates a requirement for calls to the what3words server, which reinforces the "lock-in" aspect of using the service. It also means that even if patents and copyright protections on the software were deemed to be unenforcible in court, an alternative encoding/decoding approach would require a copy of this copyrighted database in order to achieve compatibility.

These types of protection are very common for many software companies of course, and so one might put this down to the old closed-source vs open-source debate. Many in the OpenStreetMap community will favour an open approach to software anyway, but this is a choice we make. However...

what3words is fairly simple from a software point of view, and is really more about attempting establish a standard for location look-ups. It will only succeed through the network effect of persuading many people to adopt and share locations. If it does succeed, then it also succeeds in "locking in" users into the system which they have exclusive monopoly over.

The modern norm for any new simple standard, is to specify it openly and release decoding/encoding implementations as open source. This is something many people have come to expect, and to insist upon for new simple standards. This is a lesson tech experts and tech users have learned time and time again, with negative experiences of "lock-in" when private companies succeed in driving adoption of their closed systems. As such, you will tend to find people not only refuse to adopt a closed standard like what3words, but also strongly advise others not to adopt it!

No what3words codes in OSM

We don't put what3words coordinates into OpenStreetMap tags in our database. There are actually several reasons for this:

  • what3words' Terms & Conditions explicitly forbid copying their textual coordinates.[1] (So we couldn't even if we wanted to.)
  • OpenStreetMap does not support adoption of closed location referencing standards (see above)
  • We avoid putting data into OpenStreetMap which can be derived anyway in some automated way. Because
    1. it's not necessary. If you want this data, you can very easily get it without having it in an osm tag and
    2. We don't want to invite the use of automated processes for dumping in derived data. OpenStreetMap is a primary source of observed data about the world. Secondary derived data does not belong here. This principle can be seen in other areas of tagging discussion.

more mailing discussion from November 2015


In May 2016 it was adopted by the Mongolian postal service as an official addressing system for the country. The above reasoning still applies in Mongolia however.

Does this mean we're denying the people of Mongolia the ability to map their addresses? On the one hand we might say, yes. This is a small bit of pain the Mongolian postal service have inflicted upon their people by choosing a closed system (the more painful lessons will come when what3words starts leveraging their monopoly). On the other hand we're not really denying them anything, since their addresses will be auto-derivable and so they won't need to add them into OSM.


A free and open implementation of what3words's algorithm/data is not possible (Except by the company themselves. We can still hope!) but it doesn't stop some people trying. Note that the following links contain declarations of software being "open source", which is arguably misleading. We can only say "Open Source" in the sense of source code being openly available for download and use, but of course the software cannot be declared "free as in freedom" since it seems likely to be in breach of what3word's copyright or patents (Yet to be determined in a court of law, but what3word's lawyers have already strongly asserted this)

  • whatfreewords - Anonymously produced free "open source" implementation of what3words encoding/decoding in javascript, go, and python. Appearing in September 2019 and hosted annoymously, it may last longer than the following examples which were on github, however it has already been offline for a time after the initial hosts were served with a DMCA takedown. For a day or two the site had the actual document of the DMCA takedown request, including some interesting legal description of what3word's intellectual property. The site has since been re-hosted, and spawned some copy sites including whatfreewords.com. what3words' lawyers have also taken the rather surprising/extreme step of requesting twitter take-downs of various tweets linking these sites [1] [2]. There is a write-up of this story at justpaste.it/39hat purportedly written by the site's anonymous creators. Reverse engineered encoding scheme and open source implementation still exists on whatfreewords.net website.[3]

Other failed attempts:

  • User cardinalhood on github published reverse-engineered encoding/decoding code on his github account, but this was rapidly taken down with a DMCA take-down request.
  • User pudo on github set up repo called "open3words" with the intention of creating an open source what3words, however no code appeared there. Only discussion. It now seems to have mysteriously disappeared

Alternative location referencing systems using words:

  • WCodes generically encodes any data as a set of english words, and wcodes.org/location is described as an "app" of this. This is developed by Ujjwal Singh, who is the same person who seems to have prior art on the idea. The idea and source code is not yet open sourced ("to be announced").

Other location referencing systems compacting lat and lon in different ways:

  • OpenStreetMap Shortlink, specifically designed for compact URLs.
  • Xaddress, two random words and a number (designed to look a bit like an address)
  • Geohash on Wikipedia
  • plus.codes (formerly "Open Location Codes") put out by google, but fully openly
  • Volksnav
  • Maidenhead Locator System on Wikipedia, used by amateur radio operators to describe their location

Comparison including some of the above options: An Evaluation of Location Encoding Systems

Parodies of what3words:

what3fucks mischeif by User:Ivansanchez (code), spawned several variants: what3pokemon.com, what3ikea.com, what3goshdarnits.com, what3ducks.com, what3emojis.com

And another angle on the parodying... What2Numbers.org!


  1. what3words Terms & Conditions”.  "Any copying, re-utilisation, extraction, reproduction or redistribution of the content of the Intellectual Property is expressly prohibited (...)"