I still get a little giddy whenever someone asks about maps of 'Hogwarts' on phones — it feels like being handed the Marauder's Map all over again. If you mean official phone apps with an interactive, roaming map of Hogwarts: there isn’t a current Warner Bros.-released app that gives an exact, navigable Hogwarts map like the magical map from the books. There used to be more location-based experiences — remember 'Harry Potter: Wizards Unite'? It had AR and location features but it shut down in 2022. Right now the closest official things are the 'Wizarding World' app (good for news, house sorting, and collectibles) and games like 'Harry Potter: Hogwarts Mystery', which have in-game maps and room-to-room navigation but aren’t a faithful moving-map of the entire castle you can freely pan and zoom like a real-world map app.
On the fan side, though, there’s a lot of great stuff that often works well on phones through the browser. Fans have built interactive web maps that let you explore floors, common rooms, staircases, and the Forbidden Forest. Sites on Fandom, MuggleNet, and independent creators sometimes host mobile-friendly 2D or 3D maps — just be aware many unofficial apps in the App Store or Play Store called 'Marauder’s Map' or 'Hogwarts Map' pop up and vanish, due to copyright issues. I once used a browser-based 3D map on my phone while sipping coffee, zooming from the Great Hall to the Astronomy Tower; it was delightful, but crowded with pop-ups, which reminded me to check permissions and reviews before installing anything.
If you want a practical path: try a mobile-friendly fan map in your browser, follow curated threads on Reddit (r/harrypotter or fan-sites), and if you play 'Hogwarts Legacy' on console or PC the in-game map is wonderfully detailed — plenty of YouTube creators have uploaded interactive clips and annotated maps that work fine on phones. If you prefer something low-tech, a good downloadable fan-made PDF map or a custom Google My Maps with pins for locations you love can be surprisingly satisfying. Personally, I like mixing a bit of official apps (for lore and collectibles) with a trusty fan map in my browser for the actual wandering and nostalgia.