How the EV charger data works

OpenStreetMap is a free map of the world made by volunteers. A charging station in it is a point (or an outline) with the tag amenity=charging_station and, if the mapper knew more, other tags such as the operator, the plug types and the power.

This site keeps a copy of the charging stations in that data, refreshed from time to time. A charger mapped after the last collection is not in it yet, and a charger that closed since can still be there, so the page always shows the date of the collection.

A script, run by hand or on a schedule, asks a public Overpass API server for every element tagged amenity=charging_station in the world, in a few large requests and in a compact table form with only the columns this site shows, and waits between requests. It keeps the 10 tags below, drops the rest, and writes one small file per square degree of the map (a busy city is split in quarter-degree pieces). Those files are published with the site.

Visitors never talk to Overpass: your browser only reads files from this site. The files are refreshed periodically, and every result shows the date of the collection. A charger mapped after that date is not in the list yet.

Three things go wrong with volunteer data. A station can be new and not yet mapped. It can be mapped with a different tag than this page reads. And it can be out of date: closed, moved, or changed from free to paid. The date shown with a result is when this site last collected the data, not when anyone last visited the charger.

To show how stale a point may be, each result also has a “Last edit” line: the month its OpenStreetMap object was last changed, and how long before the collection that was. The bar above the list counts the points edited in the last year, between 1 and 3 years ago, and more than 3 years ago; those lines are this site’s own. A last edit is not a visit: someone may have fixed a typo without seeing the charger, and a point nobody has touched for years can still be right. Data collected before the date was kept shows “date not in this data”, and is never counted as old.

Because of all this, every result says what it does not know, and the page never shows an “available” or “working” badge. The operator’s own app is the place to check a charger’s live status.

When you press a button, the page works out which square-degree files can hold a charger inside your radius (usually one to four), downloads them from this site, measures the straight-line distance to every charger in them on your device, and shows the nearest 50. The radius starts at 3 miles and stops at 25 km. On the finder nothing is requested when the page loads (a city page is the exception: it reads the data files of its own city, a point fixed by the page, never yours), and a file already downloaded is kept in the tab’s memory, so searching again nearby downloads nothing.

Places near the 180th meridian are handled by wrapping the longitude of the files, and places near the poles by reading the whole latitude band. These are deliberate simplifications: the distances themselves are always computed correctly.

Your location never leaves your device. When you press “Use my location”, your browser asks for permission and reads your position once. The page keeps it only in the memory of the open tab, to choose the data files and to sort and map the results. It is not sent to this site, to OpenStreetMap, to any data server or to anyone else, not saved in your browser (no cookie) and not written into the address bar. It is gone when you close or reload the tab.

The one thing this site saves on your device is your plug filter: the connector types and the minimum power you pick under “My plug”. They are kept in your browser’s localStorage so they are still there next time, they never leave your device, and “Clear filters” removes them. They hold no position and no personal data.

Two things can reach other servers, and neither carries your position. The map tiles come from OpenFreeMap after you search, which sees your IP address and the tile numbers of the area you look at. And a place name you type is sent to Nominatim only when you press Search.

Every result has a “View or fix on OpenStreetMap” link. To change something you need a free OpenStreetMap account: open the object’s page, press Edit, and the editor opens with a built-in guide. Add or correct the operator, the sockets and their outputs, the opening hours, the fee and the access. The change shows up on this page after the next collection.

The OpenStreetMap wiki page for charging stations lists the tags and how to map a station, and the beginners’ guide walks through a first edit.