Why Google Maps isn't enough
Google Maps doesn't know Elba's CAI trails. For safe hiking you need a dedicated outdoor app with GPX tracks, elevation profile and offline mode (useful where mobile coverage drops, which happens often on Elba).
Wikiloc
The most used in Italy. Huge archive of community-uploaded tracks including all major Elba CAI trails. The free version allows PDF downloads; Premium offers offline GPX and live navigation. Excellent to search by trail name or CAI number.
Komoot
Better for planning. Builds an itinerary from your points of interest and calculates distance, elevation, time. Offline maps are a one-time purchase per region (central Italy covers Elba). Excellent for MTB.
Maps.me
Free, light, fully offline. Not trekking-specific but includes OSM trails, so all Elba CAI routes are there. Built-in compass. Ideal as backup when your phone is on standby all day.
AllTrails
Very popular in English-speaking countries, excellent UX. Elba trail map is there, reviews are in English and varied. Premium for offline. Good choice if you're used to Strava-style apps.
Practical tip
Install at least two apps: a primary one (Wikiloc or Komoot) and Maps.me as offline backup. Download tracks before leaving from your hotel Wi-Fi. In the mountains battery drains faster: bring a power bank.