About this tool

HERE Polyline Decoder is a fully interactive tool designed to help developers and GIS users work with HERE Flexible Polyline format.

You can paste any polyline string to instantly validate its correctness, decode it into coordinates, and visualize the resulting geometry on a Leaflet map. The tool highlights incorrect formats, provides detailed error messages, and allows you to quickly understand whether the polyline data is usable.

The decoder also includes a built-in converter that transforms polyline data into clean, standards-compliant GeoJSON. The resulting GeoJSON is displayed in a separate read-only window, where it can be copied or saved as a file. You can also perform the reverse operation: paste a GeoJSON LineString into the GeoJSON window and automatically convert it back into HERE polyline format.

To support interactive workflows, the map integrates search autocomplete for addresses, letting you center the map or drop markers at precise locations. Additional tools allow you to clear data, copy values to clipboard, save both formats to files with timestamped filenames, and toggle visibility of the GeoJSON panel.

Overall, the application serves as a compact, developer-friendly environment for verifying polyline data, converting between formats, previewing geometry in real time, and working efficiently with location-based datasets.