GDAL in the browser.
And now on mobile.

// vite.config.ts, one line:  plugins: [cppjs()]
import 'gdal3.js/Dataset.h';
import { initCppJs, Gdal } from 'gdal3.js/Gdal.h';

const Module = await initCppJs({ useWorker: true, fs: { opfs: true } });

// put the user's file into OPFS; gdal sees it as /opfs/…
const dir = await navigator.storage.getDirectory();
const fh  = await dir.getFileHandle(file.name, { create: true });
const ws  = await fh.createWritable(); await ws.write(file); await ws.close();

const ds   = await Gdal.open(`/opfs/${file.name}`);
const opts = await Module.toVector('VectorString',
  ['-f', 'GPKG', '-t_srs', 'EPSG:3857']);
const out  = await ds.vectorTranslate('/opfs/out.gpkg', opts);
await out.close();  // out.gpkg persists in OPFS, survives reloads

// Bundle with @cpp.js/plugin-rollup or -webpack targeting Node,
// or use the prebuilt Node build from @gdal3.js/wasm-bundle.
import 'gdal3.js/Dataset.h';
import { initCppJs, Gdal } from 'gdal3.js/Gdal.h';

const Module = await initCppJs();  // Node: host filesystem, no VFS hop

const ds   = await Gdal.open('data/districts.gpkg');
const opts = await Module.toVector('VectorString',
  ['-f', 'GeoJSON', '-t_srs', 'EPSG:4326']);
const out  = await ds.vectorTranslate('out/districts.geojson', opts);
await out.close();

// metro.config.js: wrap once with the cpp.js Metro plugin.
// Native module builds at pod-install / gradle time. Same imports as web:
import 'gdal3.js/Dataset.h';
import { initCppJs, Gdal } from 'gdal3.js/Gdal.h';
import * as DocumentPicker from 'expo-document-picker';
import * as FileSystem from 'expo-file-system/legacy';

const Module = await initCppJs();  // real native GDAL over JSI, no wasm

const picked = await DocumentPicker.getDocumentAsync();
const path   = picked.assets[0].uri.replace('file://', '');

const ds   = await Gdal.open(path);
const opts = await Module.toVector('VectorString', ['-f', 'GPKG']);
const out  = await ds.vectorTranslate(
  `${FileSystem.cacheDirectory.replace('file://', '')}out.gpkg`, opts);

// No bundler on Workers: the self-contained single-threaded edge build, no plugin.
// Full 189-driver build is large; size-capped Workers need wasm-bundle-minimal (WIP).
import { initCppJs, Gdal } from '@gdal3.js/wasm-bundle';

export default {
  async fetch(request) {
    const Module = await initCppJs();  // single-threaded, in-memory FS

    const bytes = new Uint8Array(await request.arrayBuffer());
    await Gdal.fileFromMemBuffer('/vsimem/in.geojson', bytes);

    const ds   = await Gdal.open('/vsimem/in.geojson');
    const opts = await Module.toVector('VectorString',
      ['-f', 'GPKG', '-t_srs', 'EPSG:3857']);
    const out  = await ds.vectorTranslate('/vsimem/out.gpkg', opts);
    await out.close();

    return new Response(Module.FS.readFile('/vsimem/out.gpkg'));
  },
};

<!-- The stable v2 line is on npm today; drop into any page. -->
<script src="https://cdn.jsdelivr.net/npm/gdal3.js@2.8.1/dist/package/gdal3.js"></script>
<script>
  initGdalJs({
    path: 'https://cdn.jsdelivr.net/npm/gdal3.js@2.8.1/dist/package',
  }).then(async (Gdal) => {
    const f     = document.querySelector('input[type=file]').files[0];
    const input = await Gdal.open(f);
    const out   = await Gdal.ogr2ogr(input.datasets[0],
      ['-f', 'GeoJSON', '-t_srs', 'EPSG:4326']);
    const bytes = await Gdal.getFileBytes(out);
  });
</script>