Map Extender

Hook into Leaflet and Google Maps to run custom JavaScript plugins — your own markers, overlays, and map tools.

Map Extender turns any Leaflet or Google Maps embed into a platform for your own map tools. Write a small plugin once, and it runs automatically on every matching site — no browser console hacks, no re-pasting scripts, no losing your work on refresh. Key features: Automatic map detection — Map Extender finds Leaflet and Google Maps instances on the page, including maps embedded in cross-origin iframes, and connects to them for you. Your own plugins — Write plugins in plain JavaScript that add markers, lines, overlays, and click handlers to the map. Choose exactly which sites each plugin runs on using match patterns, then turn it on or off per site from the popup. Built-in editor — A code editor with syntax highlighting, a match-pattern manager, a settings form for your plugin's configurable options, and a live log panel for debugging — no separate IDE required. Built-in starter plugins — Comes with ready-to-use examples: a distance measuring tool, train station markers, a railway overlay, a GeoJSON/GPX file viewer, a dark-map filter, and a public-transport finder. Plugin registries — Want more? Add a registry: a list of plugins published by someone else. You paste its address, browse what it offers, read the source code of anything before you install it, and switch on only what you want. The extension comes with no registries and downloads nothing until you add one. Runs locally, stays private — Your plugin code, settings, and per-site preferences are stored only in your browser. Map Extender doesn't run its own servers and doesn't track your browsing. How to use it: 1. Open a page with a Leaflet or Google Map and click the Map Extender icon to confirm it's connected. 2. Click "Open Plugins" to write a new plugin or enable one of the built-in ones. 3. Set which sites the plugin should run on, save it, and toggle it on from the popup. 4. Refine your plugin's code and settings any time — saved changes apply to open pages straight away, no reload needed. Because plugins are just JavaScript, you can also ask an AI assistant to write one for you — the project's plugin API reference is designed to be pasted straight into a chat. Map Extender runs entirely in your browser — no accounts, no servers, no tracking. See the privacy policy linked on this listing for full details on permissions and data handling. Questions or feedback? Reach out through the support link on this listing page.