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Adapters

PouchDB is not a self-contained database; it is a CouchDB-style abstraction layer over other databases. By default, PouchDB ships with IndexedDB and WebSQL adapters in the browser, and a LevelDB adapter in Node.js. This can be visualized as so:

adapters

PouchDB attempts to provide a consistent API that "just works" across every browser and JavaScript environment, and in most cases, you can just use the defaults. However, if you're trying to reach the widest possible audience, or if you want the best performance, then you will sometimes want to tinker with the adapter settings.

Topics:

In the browser, PouchDB prefers IndexedDB, and falls back to WebSQL if IndexedDB is not available. As of 2015, the browser support looks like this:

Desktop

IE Firefox Chrome Safari Opera
Adapter IE Firefox Chrome Safari Opera
IndexedDB ✓ (10+)
WebSQL

Mobile

Safari iOS Opera Android BlackBerry Opera Chrome for Android Firefox for Android IE
Adapter iOS Safari Opera Mini Android Browser BlackBerry Browser Opera Mobile Chrome for Android Firefox for Android IE Mobile
IndexedDB ✓ (4.4+) ✓ (10+) ✓ (21+)
WebSQL
Safari 7.1+ and iOS 8+ supposedly support IndexedDB, but their implementation has many bugs, so PouchDB currently ignores it.

If you're ever curious which adapter is being used in a particular browser, you can use the following method:

var pouch = new PouchDB('myDB');
console.log(pouch.adapter); // prints either 'idb' or 'websql'

SQLite plugin for Cordova/PhoneGap

On Cordova/PhoneGap/Ionic, the native SQLite database is often a popular choice, because it allows unlimited storage (compared to IndexedDB/WebSQL storage limits). It also offers more flexibility in backing up and pre-loading databases, because the SQLite files are directly accessible to app developers.

There are various Cordova plugins that can provide access to native SQLite, such as Cordova-sqlite-storage,
cordova-plugin-sqlite-2, or cordova-plugin-websql.

To use them, you must install them separately into your Cordova application, and then add a special third-party PouchDB adapter called pouchdb-adapter-cordova-sqlite. Once you do that, you can use it via:

var db = new PouchDB('myDB.db', {adapter: 'cordova-sqlite'});
In PouchDB pre-6.0.0, Cordova SQLite support was available out-of-the-box, but it has been moved to a separate plugin to reduce confusion and to make it explicit whether you are using WebSQL or Cordova SQLite.

We recommend avoiding Cordova SQLite unless you are hitting the 50MB storage limit in iOS, you require native or preloaded access to the database files, or there's some other reason to go native. The built-in IndexedDB and WebSQL adapters are nearly always more performant and stable.

Browser adapter plugins

PouchDB also offers separate browser plugins that use backends other than IndexedDB and WebSQL. These plugins fully pass the PouchDB test suite and are rigorously tested in our CI process.

Downloads:

These plugins add a hefty footprint due to external dependencies, so take them with a grain of salt.

In-memory adapter

If you want a quick database for your unit tests, you can use the pouchdb.memory.js plugin, which offers a pure in-memory PouchDB:

<script src="pouchdb.js"></script>
<script src="pouchdb.memory.js"></script>
<script>
  // this pouch is ephemeral; it only exists in memory
  var pouch = new PouchDB('mydb', {adapter: 'memory'});
</script>

This pouch will act exactly like a normal one – replicating, storing attachments, pagination, etc. – but it will be deleted as soon as the user closes their browser. However, multiple PouchDB objects with the same database name will share the same data:

// pouch1 and pouch2 will share the same data
var pouch1 = new PouchDB('myDB', {adapter: 'memory'});
var pouch2 = new PouchDB('myDB', {adapter: 'memory'});

// pouch3 will have its own data
var pouch3 = new PouchDB('myOtherDB', {adapter: 'memory'});

LocalStorage adapter

If you need to support very old browsers, such as IE ≤ 9.0 and Opera Mini, you can use the pouchdb.localstorage.js plugin, which allows PouchDB to fall back to LocalStorage on browsers that don't support either IndexedDB or WebSQL. The es5-shims will also be necessary.

<script src="pouchdb.js"></script>
<script src="pouchdb.localstorage.js"></script>
<script>
  // this pouch is backed by LocalStorage
  var pouch = new PouchDB('mydb', {adapter: 'localstorage'});
</script>
The LocalStorage plugin should be considered highly experimental, and the underlying structure may change in the future. Currently it stores all document IDs in memory, which works fine on small databases but may crash on larger databases. You can follow localstorage-down to track our progress.

FruitDOWN adapter

If you need to support IndexedDB in Apple browsers (which PouchDB normally does not support due to instability), then you can use FruitDOWN, which works over all IndexedDB implementations at the expense of using a much smaller part of the IndexedDB API and therefore being slower and less efficient.

<script src="pouchdb.js"></script>
<script src="pouchdb.fruitdown.js"></script>
<script>
  // this pouch is backed by FruitDOWN
  var pouch = new PouchDB('mydb', {adapter: 'fruitdown'});
</script>

In Node.js, the adapter situation is much simpler than in browsers. By default, if you create a PouchDB like this one:

var pouch = new PouchDB('./path/to/db');

then a LevelDB-based database will be created in the directory ./path/to/db. The LevelDB implementation uses LevelDOWN.

In-memory

Just as in the browser, you can also create a pure in-memory PouchDB:

$ npm install pouchdb-adapter-memory

then:

PouchDB.plugin(require('pouchdb-adapter-memory'));
var pouch = new PouchDB('myDB', {adapter: 'memory'});

This implementation is based on MemDOWN, and will not write any changes to disk.

Node SQLite adapter

You can also use PouchDB over SQLite3 in Node, using the WebSQL adapter and node-websql:

var PouchDB = require('pouchdb');
PouchDB.plugin(require('pouchdb-adapter-node-websql'));

var db = new PouchDB('mydatabase.db', {adapter: 'websql'});

In this case, PouchDB is directly using SQLite queries to build the database, exactly as the WebSQL adapter would.

See "Prebuilt databases with PouchDB" for a guide to how you might use this adapter to create prebuilt SQLite database files for adapters such as Cordova or Electron.

Other LevelDOWN adapters

Technically you are free to use any LevelDOWN-based implementation in either Node or the browser. However this should be considered extremely experimental and not designed for production use.

See pouchdb-adapter-leveldb-core for details.

In both the browser and in Node.js, PouchDB can also function as a straightforward API on top of any CouchDB-compliant database:

var pouch = new PouchDB('http://my-site.com:5984/my-db');
var securePouch = new PouchDB('https://my-secure-site.com:5984/my-secure-db');

You can also sync to and from these databases to your local PouchDB.

Currently PouchDB has full support for:

Couchbase Sync Gateway support is in progress. It will work, but you may run into issues, especially with attachments. Drupal 8 has also announced support for PouchDB, and there is rcouch as well, but these are both untested by PouchDB.

If you are ever unsure about a server, consider replicating from PouchDB to CouchDB, then from that CouchDB to the other server.

PouchDB Server

PouchDB Server is a standalone REST server that implements the CouchDB API, while using a LevelDB-based PouchDB under the hood. It also supports an --in-memory mode and any LevelDOWN adapter, which you may find handy.

PouchDB Server passes the PouchDB test suite at 100%, but be aware that it is not as full-featured or battle-tested as CouchDB.

PouchDB Express

The underlying module for PouchDB Server, Express PouchDB is an Express submodule that mimics most of the CouchDB API within your Express application.

The best place to look for information on which browsers support which databases is caniuse.com. You can consult their tables on browser support for various backends: