Copy Chrome localStorage entries from one origin to another (rewrites LevelDB directly)

migrate.js

#!/usr/bin/env node
// Copies Chrome localStorage entries from one origin to another.
// Chrome must be closed before running.
//
// Usage:
//   node migrate.js <old-origin> <new-origin> [chrome-profile-path]
//
// Examples:
//   node migrate.js https://old.example.com https://new.example.com
//   node migrate.js https://old.example.com https://new.example.com "/path/to/Chrome/Default"

'use strict';

const { Level } = require('level');
const fs = require('fs');
const path = require('path');
const os = require('os');

function getDefaultChromePaths() {
  const home = os.homedir();
  switch (process.platform) {
    case 'darwin':
      return [
        path.join(home, 'Library/Application Support/Google/Chrome/Default'),
        path.join(home, 'Library/Application Support/Chromium/Default'),
        path.join(home, 'Library/Application Support/Google/Chrome Beta/Default'),
      ];
    case 'win32':
      return [
        path.join(process.env.LOCALAPPDATA || '', 'Google/Chrome/User Data/Default'),
        path.join(process.env.LOCALAPPDATA || '', 'Chromium/User Data/Default'),
        path.join(process.env.LOCALAPPDATA || '', 'Google/Chrome Beta/User Data/Default'),
      ];
    default: // Linux and other POSIX
      return [
        path.join(home, '.config/google-chrome/Default'),
        path.join(home, '.config/chromium/Default'),
        path.join(home, '.config/google-chrome-beta/Default'),
        path.join(home, 'snap/chromium/common/chromium/Default'),
      ];
  }
}

function findDbPath(profilePath) {
  const candidates = profilePath
    ? [profilePath]
    : getDefaultChromePaths();

  for (const p of candidates) {
    const dbPath = path.join(p, 'Local Storage/leveldb');
    if (fs.existsSync(dbPath)) return dbPath;
  }
  return null;
}

async function migrate(oldOrigin, newOrigin, dbPath) {
  console.log(`DB:  ${dbPath}`);
  console.log(`From: ${oldOrigin}`);
  console.log(`To:   ${newOrigin}\n`);

  // Warn if LOCK file suggests Chrome might be open
  const lockFile = path.join(dbPath, 'LOCK');
  if (fs.existsSync(lockFile) && fs.statSync(lockFile).size > 0) {
    console.warn('WARNING: LOCK file is non-empty — Chrome may still be running. Proceed at your own risk.\n');
  }

  const db = new Level(dbPath, { keyEncoding: 'buffer', valueEncoding: 'buffer' });
  await db.open();

  const oldDataPrefix = Buffer.from(`_${oldOrigin}\x00\x01`);
  const oldMetaKey   = Buffer.from(`META:${oldOrigin}`);
  const oldAccessKey = Buffer.from(`METAACCESS:${oldOrigin}`);

  const toWrite = [];
  const found = [];

  for await (const [key, value] of db.iterator()) {
    const keyBin = key.toString('binary');
    if (key.equals(oldMetaKey)) {
      toWrite.push({ type: 'put', key: Buffer.from(`META:${newOrigin}`), value });
      found.push(`META:${newOrigin}`);
    } else if (key.equals(oldAccessKey)) {
      toWrite.push({ type: 'put', key: Buffer.from(`METAACCESS:${newOrigin}`), value });
      found.push(`METAACCESS:${newOrigin}`);
    } else if (keyBin.startsWith(oldDataPrefix.toString('binary'))) {
      const suffix = keyBin.slice(oldDataPrefix.toString('binary').length);
      toWrite.push({ type: 'put', key: Buffer.from(`_${newOrigin}\x00\x01${suffix}`), value });
      found.push(`  ${suffix}`);
    }
  }

  if (toWrite.length === 0) {
    console.log(`No localStorage entries found for ${oldOrigin}`);
    await db.close();
    return;
  }

  console.log(`Found ${toWrite.length} entries:`);
  for (const k of found) console.log(`  ${k}`);

  await db.batch(toWrite);
  console.log(`\nWrote ${toWrite.length} entries to ${newOrigin}`);
  await db.close();
}

// ── main ──────────────────────────────────────────────────────────────────────

const [,, oldOrigin, newOrigin, profileArg] = process.argv;

if (!oldOrigin || !newOrigin) {
  console.error('Usage: node migrate.js <old-origin> <new-origin> [chrome-profile-path]');
  console.error('Example: node migrate.js https://old.example.com https://new.example.com');
  process.exit(1);
}

const dbPath = findDbPath(profileArg);
if (!dbPath) {
  console.error('Could not find Chrome localStorage directory. Pass it explicitly as the third argument.');
  process.exit(1);
}

migrate(oldOrigin, newOrigin, dbPath).catch(err => {
  console.error(err.message || err);
  process.exit(1);
});

package.json

{
  "name": "chrome-localstorage-origin-migrate",
  "version": "1.0.0",
  "description": "Copy Chrome localStorage entries from one origin to another by rewriting the underlying LevelDB",
  "main": "migrate.js",
  "bin": {
    "chrome-ls-migrate": "migrate.js"
  },
  "scripts": {
    "start": "node migrate.js"
  },
  "keywords": ["chrome", "localstorage", "leveldb", "migrate"],
  "license": "MIT",
  "type": "commonjs",
  "dependencies": {
    "level": "^10.0.0"
  }
}