You could try the figure out your own route through the city using just the Paris Metro maps in every station and at every stop, but that would be a huge hassle when you can just use the free
NextStopParis app provided by the RATP which is the transit authority. The app is not perfect, but as far as transit apps go it is pretty well put together.
Make sure that you download the app before you get to Paris. This is especially true if you are not going to have cell service while you are in Paris, but is good practice even if you are. Once you have the app downloaded on your phone make sure you open it so that it can download the offline maps for you.
In the app you will most often use the option at the top of the main screen to get direction to a specific location. All of the main tourist attractions are in the app, if you need to get somewhere else such as a restaurant or hotel it is easiest to just find out which metro stop is nearest to it and navigate to that.
If you are planning your days and you want to know how to get from one spot to another, or if your GPS is not working, you can hit the plus sign below the destination bar to get the full options.
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