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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.

Non-open patented addressing 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.
  • 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 address) 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 addresses in OSM

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

  • 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 A) it's not necessary. If you want this data, you can very easily get it without having it in an osm tag and B) 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 see 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.


Other location referencing systems using three words:
There are none, and the idea is patented (boo!) Mind you...

An Evaluation of Location Encoding Systems

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

Parodies of what3words: