GIS Toolbox is a browser-based suite of 25 GIS tools. It converts coordinates between WGS84, Web Mercator, UTM and 100+ EPSG codes, and converts between Shapefile, GeoJSON, KML, CSV, TopoJSON and PMTiles. It also offers batch ZIP, GeoTIFF support, 2D and 3D measurement, a LAS/LAZ point cloud viewer and a hyperspectral explorer.
The site shows a badge reading 100% LOCAL, 0 B UPLOADED and says files never leave your browser, which are the site's own claims. A Pricing link exists but no tiers are shown on the landing page.
Converting coordinates and spatial files usually means desktop GIS software or uploading data. GIS Toolbox runs those conversions in the browser instead.