# Leaflet [Leaflet ](https://leafletjs.com/)is an open-source JavaScript library for displaying interactive maps on the web or mobile. A simple and lightweight library that will enable you to display and visualise location data and build dynamic applications. ## What you'll need * OS Maps API and OS NGD API – Features added to an API project in the OS Data Hub with an API Key. See [Getting started with an API project](https://app.gitbook.com/s/oEzqrBzRGoJw7nQyLj1W/core-concepts/getting-started-with-an-api-project "mention") for more information. * A text editor like Visual Studio Code or Notepad to edit and save your HTML and JavaScript files. {% stepper %} {% step %} ### Set up your HTML file * Create a new HTML file with a text editor (for example, Notepad, Visual Studio Code). * Add the basic HTML structure to your file with a placeholder `
` for the map. {% code overflow="wrap" %} ```html OS NGD API – Features | Template (EPSG:3857) | Leaflet
``` {% endcode %} {% endstep %} {% step %} ### Insert your API Key and OS NGD collection * To enable access to OS APIs an API Key is required. Inside the `