What3words

What3Words (W3W) is a proprietary geolocation system developed by What3Words Limited, assigning three-word combinations to 3×3 meter squares across the globe. It is marketed as a simple alternative to latitude/longitude for navigation, logistics, and emergency services. The system is entirely closed-source and is protected by patents, copyrighted wordlists, and trademarks. Although widely promoted for consumer use, What3Words has been the subject of significant criticism from security researchers, mapping experts, emergency response professionals, and open-data advocates. Criticisms focus on its proprietary nature, licensing restrictions, algorithmic opacity, similarity-based errors in safety-critical contexts, and the company’s history of issuing legal threats against researchers who attempted to analyze or replicate the system.^[1][2]

• User Freedom: Limited; closed-source design, restrictive API license, and prohibitions on independent implementations.^[3]
• Transparency: Poor; the algorithm, wordlists, and error handling are not publicly auditable.
• Business Model: Proprietary licensing, metered API access, and restrictions on redistribution of derived data.^[4]
• Market Competition: Faces criticism compared to open alternatives such as Plus Codes, traditional coordinates, and Mapcodes.
• Public Safety Impact: Mixed; documented cases of miscommunication and near-miss incidents have raised concern among emergency services.^[5]

• In April 2021, What3Words—through law firm JA Kemp—issued a legal threat to security researcher Aaron Toponce, demanding deletion of tweets referencing the open-source “WhatFreeWords” project, disclosure of any recipients, and removal of all copies of the software.*^[1]

TechCrunch reported that What3Words claimed the project contained proprietary data and binary information, although it did not seek removal of criticism.^[1]

• What3Words previously pursued takedown actions targeting the WhatFreeWords website and related tweets, including a DMCA request and a WIPO complaint that resulted in domain seizure in 2020.*^[6]
• These threats are documented in the Disclose.io database of legal threats against researchers,* including entries from September 2019 and April 2021.^[7]

The OpenStreetMap community characterizes W3W as a “closed system,” noting its use of patented algorithms, encrypted wordlists, copyright protection, and trademark restrictions that prevent interoperability or integration with open datasets.^[3] What3Words’ API Licence Agreement further restricts usage by defining “What3Words Data” broadly, imposing request limits, and requiring prior approval for NGO use exceeding 75,000 monthly API calls.^[4] The OpenStreetMap Foundation’s licensing guidance identifies structural incompatibilities between W3W’s restrictive terms and ODbL-licensed open data, advising against use of proprietary addressing schemes in open geographic projects.^[8]

Multiple BBC investigations documented incidents where What3Words locations were miscommunicated or incorrect in emergency scenarios:

• Mountain Rescue England and Wales reported dozens of cases of callers giving incorrect W3W addresses due to spelling errors, accents, or similar-sounding word triplets.*^[2]
• A Keswick Mountain Rescue incident placed a casualty miles away from their true location when a misheard W3W address was given; PhoneFind provided the correct grid reference.*^[5]

Security researcher Andrew Tierney demonstrated that many W3W squares contain highly similar three-word addresses, increasing risk in safety-critical situations; BBC coverage echoed these findings and W3W’s claim that its “Autosuggest” feature mitigates errors.^[5]

What3Words holds multiple U.S. patents related to candidate word suggestion, error correction, and mapping input strings to wordlists, including:

• US Patent 10,909,318 – “Method for suggesting one or more multi-word candidates…” (Granted Feb 2, 2021).^[9]
• US Patent 11,017,169 – “Method for suggesting candidate words as replacements…” (Granted May 25, 2021).^[10]

What3Words also disclosed IPR to the IETF for draft-saywhere, referencing CA2909524A1.^[11]

In response to criticism, What3Words frequently asserts that:

• Human error can occur with any addressing system,* and W3W’s Autosuggest is designed to reduce ambiguous input.^[2]
• Communication errors also occur with coordinates or grid references,* a point highlighted in BBC interviews during coverage of emergency mislocation incidents.^[5]

In TechCrunch’s coverage of legal threats, CEO Chris Sheldrick stated that enforcement actions targeted unauthorized copies containing proprietary binary material and that W3W was not seeking to suppress criticism.^[1]