I use a number of mapping/route planning apps to work out my way around the UK’s countryside, but the one I use the most is called Footpath. It is available on both Apple and Android.
The free version allows you to create and save five routes to your device, which is just fine if:
a) you’re not a big walk route planner (I do realise I am in the minority) and/or
b) you only want to be able to open and follow routes that I plot and share
On this site (and in the information for each location on the walk locations map), I’ll be sharing Footpath routes for walks I have plotted out. If you download the app to your mobile/tablet, when you click on those route links, they’ll open in your app.
You can still see the routes in your browser if you don’t download the app, but the experience in the app is far superior – and you’ll be able to see yourself on the route as a blue marker. You’ll also be able to save routes I’ve created to your device if you want.

The Footpath website has a useful user guide.
