H3 Flutter Plus

h3_flutter_plus is the official Flutter package in the modern Dart/Flutter H3 ecosystem. It provides seamless support for Uber’s H3 library across all platforms including mobile, desktop, and web.

This package is built on top of h3_dart_plus, using h3_ffi_plus and h3_web_plus under the hood.

Example

import 'package:h3_flutter_plus/h3_flutter_plus.dart';

final h3 = const H3Factory().load();
final hexagons = h3.polygonToCells(
  resolution: 6,
  coordinates: [
    LatLng(lat:37.775, lng:-122.418),
    LatLng(lat:37.776, lng:-122.419),
    LatLng(lat:37.777, lng:-122.417),
  ],
);

final geojson2h3 = Geojson2H3(h3);

Setup

Mobile / Desktop

Simply add h3_flutter_plus to your pubspec.yaml, import it, and call H3Factory().load().

import 'package:h3_flutter_plus/h3_flutter_plus.dart';

final h3 = const H3Factory().load();

Web

Web support is based on h3-js v4.2.1. You must include the script manually in your index.html:

<script defer src="https://unpkg.com/h3-js@4.2.1"></script>

Make sure this comes before your main.dart.js script.

final h3 = const H3Factory().load();

⚠️ Web Notice: When using on web, always null-check the output of H3 methods even if the Dart analyzer marks them as safe. This is due to an issue in Dart's JS interop FFI generator affecting null safety. This will be improved in future releases.

Geojson2H3 Support

Basic GeoJSON utilities from geojson2h3 are supported via the Geojson2H3 class. It is a drop-in replacement provided via geojson2h3_plus.

final geojson = const Geojson2H3(h3);

History & Migration

This package is the successor of the original h3_flutter package. The original was based on H3 v3.7.2 and used legacy Dart FFI and JS bindings.

The new h3_flutter_plus package is part of a full rewrite of the Dart H3 bindings ecosystem for H3 v4.2.1, introducing:

• Updated C bindings via h3_ffi_plus
• Web support with h3-js@4.2.1 via h3_web_plus
• Exception-safe, null-safe Dart wrappers
• Vertex mode and experimental feature support

All packages in the *_plus family are actively maintained and provide a clean, consistent API surface across platforms.