My daily train commute has no reliable internet, which eliminated most language apps that require constant connectivity. I needed offline grammar practice that would not drain my phone battery or require streaming.
Conjugaison Française Larousse works completely offline
This app stores verb conjugations locally, so I can look up any verb form without data. The search is fast enough that I use it while reading French articles on my phone, checking conjugations without losing my place in the text. It includes seventeen tenses and shows which verbs follow irregular patterns.
French Grammar in Use has downloadable exercises
Cambridge's app lets you download entire units before you lose connection. Each unit covers one grammar point with twenty practice sentences. The explanations are brief but include enough examples to understand the concept. Progress syncs when you reconnect, but all practice happens locally.
Why most popular apps did not work
Duolingo requires internet for new lessons. Babbel downloads content but the grammar explanations are minimal. Memrise focuses on vocabulary over grammar structure. These apps work well for other purposes but did not solve my specific need for offline grammar practice during a thirty-eight minute commute.
I downloaded both apps once and have used them on trains, planes, and waiting rooms for eighteen weeks. They turned dead time into focused grammar review without requiring connectivity or subscriptions.