https://organicmaps.app/:

Organic Maps is a free Android & iOS offline maps app for travelers, tourists, hikers, drivers and cyclists based on OpenStreetMap data created by the community. It is a privacy-focused, open-source fork of […]

Organic Maps is one of the few applications nowadays that supports 100% of features without an active Internet connection. Install Organic Maps, download maps, throw away your SIM card, and go for a weeklong trip on a single battery charge without any byte sent to the network.

Positive impressions:

  • works great on iOS (didn’t test on Android yet)
  • a great companion for cycling within the city
  • more fun and more lightweight than Google Maps
  • low impact on device battery life
  • extremely privacy friendly (no ads, no tracking, no push notifications, etc)
  • extremely mobile data friendly (works fully offline)
  • open-source, and without any IAP
  • works out-of-the-box, no sign up necessary

Negative impressions:

  • do not use it for public transit, it is terrible as it does not have real-time data integration