The free what3words app works offline. Use it to find the 3 word address for your current location, or enter a 3 word address and use Compass Mode to navigate there.
Other apps including Navmii, Pocket Earth and Viewranger also allow you to search for a what3words address, see it on a map and navigate there – all without an internet connection.
See our CEO Chris explain using what3words offline here. You can also see an up-to-date list of apps, tools and services that accept what3words on our Products page.