Capacitor app crashes while writing large JSON file using Filesystem.writeFile()

Question

I'm building an Ionic + Capacitor app that uses the @capacitor-community/sqlite plugin for local database storage. I'm trying to export the entire SQLite database as a JSON backup file and save it using Capacitor’s Filesystem API.

import { Filesystem, Directory, Encoding } from '@capacitor/filesystem';
import { CapacitorSQLite, capSQLiteJson } from '@capacitor-community/sqlite';

const sqlite = CapacitorSQLite;

async function backupDatabase() {
  try {
    const db = await sqlite.createConnection('my_db', false, 'no-encryption', 1);
    await db.open();

    const jsonObj: capSQLiteJson = await db.exportToJson('full');

    await Filesystem.writeFile({
      path: 'backup.json',
      data: JSON.stringify(jsonObj.export),
      directory: Directory.Documents,
      encoding: Encoding.UTF8
    });

    console.log('Backup completed successfully');
  } catch (err) {
    console.error('Backup failed:', err);
  }
}

It works fine for smaller databases, but the app crashes when the JSON becomes large (around 50MB or more). No specific error is thrown — it just freezes or closes unexpectedly during the writeFile() operation.

50 MB seems a bit early for a crash, but there's a limit for string length: stackoverflow.com/questions/44533966/… — tevemadar
– tevemadar, Commented Nov 5 at 12:49

Sa E Chowdary · Accepted Answer · 2025-11-11 10:42:50Z

Option 1: Let the SQLite plugin save directly to a file (best for large backups)

The @capacitor-community/sqlite plugin supports exporting the database as a file — so you don’t need to serialize large JSON across the bridge.

Instead of using exportToJson() and Filesystem.writeFile(), use the plugin’s backupToStore() or exportToJson({jsonexportmode: 'full'}) + native save methods.

For example:

const db = await sqlite.createConnection('my_db', false, 'no-encryption', 1);
await db.open();

// Create a backup file managed by the plugin
await db.backupToStore('backup_file'); // creates 'backup_file.db' in plugin storage

console.log('Database backup completed successfully');

Then, if you need to export that file for sharing or uploading, use the plugin’s getUrl() or copy the file from the plugin’s database folder using native filesystem APIs — not via the JS bridge.

✅ This avoids JSON serialization and the huge string transfer problem.

Option 2: Stream or chunk the JSON write

If you must use JSON (for example, for cloud sync), don’t write it in one massive call.

Instead, write it in chunks:

import { Filesystem, Directory, Encoding } from '@capacitor/filesystem';
import { CapacitorSQLite } from '@capacitor-community/sqlite';

const CHUNK_SIZE = 5000000; // ~5MB

async function backupLargeJSON() {
  const db = await CapacitorSQLite.createConnection('my_db', false, 'no-encryption', 1);
  await db.open();

  const jsonObj = await db.exportToJson('full');
  const jsonStr = JSON.stringify(jsonObj.export);

  // Split into smaller parts
  for (let i = 0; i < jsonStr.length; i += CHUNK_SIZE) {
    const chunk = jsonStr.slice(i, i + CHUNK_SIZE);
    await Filesystem.appendFile({
      path: 'backup.json',
      data: chunk,
      directory: Directory.Documents,
      encoding: Encoding.UTF8,
    });
  }

  console.log('Backup completed successfully');
}

⚠️ This is slower but prevents the JS bridge from choking on a single large payload.

Option 3: Skip JSON entirely — just copy the raw SQLite database file

If you don’t need JSON for migration between platforms, just back up the .db file itself:

const dbPath = await sqlite.getDatabasePath('my_db');

// Now copy this file using native Filesystem plugin or share it
await Filesystem.copy({
  from: dbPath,
  to: 'Documents/backup_my_db.sqlite',
});

This is far more efficient — no JSON serialization, no large JS objects, and very fast.

Thanks! But the methods backupToStore and getDatabasePath don’t exist in the official @capacitor-community/sqlite plugin or typings. I also tried chunking, but the app still crashes once the JSON size grows — around 400K records or 80MB+. I only need offline backup/restore on Android (no cloud sync). Looking for a working native approach that handles large DBs reliably.

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Capacitor app crashes while writing large JSON file using Filesystem.writeFile()

1 Answer 1

Option 1: Let the SQLite plugin save directly to a file (best for large backups)

Option 2: Stream or chunk the JSON write

Option 3: Skip JSON entirely — just copy the raw SQLite database file

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Collectives™ on Stack Overflow

1 Answer 1

Option 1: Let the SQLite plugin save directly to a file (best for large backups)

Option 2: Stream or chunk the JSON write

Option 3: Skip JSON entirely — just copy the raw SQLite database file

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