Fake IndexedDB: a pure JS in-memory implementation of the IndexedDB API
npm install fake-indexeddb
A pure JS in-memory implementation of the IndexedDB API. Its main use is testing IndexedDB-dependent code in Node.js.
``sh`
npm install --save-dev fake-indexeddb
Functionally, it works exactly like IndexedDB except data is not persisted to disk.
The easiest way to use it is to import fake-indexeddb/auto, which will put all the IndexedDB variables in the global scope. (Both import and require are supported, use whichever you like, but the examples here are all import.)
`js
import "fake-indexeddb/auto";
var request = indexedDB.open("test", 3);
request.onupgradeneeded = function () {
var db = request.result;
var store = db.createObjectStore("books", {keyPath: "isbn"});
store.createIndex("by_title", "title", {unique: true});
store.put({title: "Quarry Memories", author: "Fred", isbn: 123456});
store.put({title: "Water Buffaloes", author: "Fred", isbn: 234567});
store.put({title: "Bedrock Nights", author: "Barney", isbn: 345678});
}
request.onsuccess = function (event) {
var db = event.target.result;
var tx = db.transaction("books");
tx.objectStore("books").index("by_title").get("Quarry Memories").addEventListener("success", function (event) {
console.log("From index:", event.target.result);
});
tx.objectStore("books").openCursor(IDBKeyRange.lowerBound(200000)).onsuccess = function (event) {
var cursor = event.target.result;
if (cursor) {
console.log("From cursor:", cursor.value);
cursor.continue();
}
};
tx.oncomplete = function () {
console.log("All done!");
};
};
`
Alternatively, you can explicitly import individual IndexedDB variables:
`js
import {
indexedDB,
IDBCursor,
IDBCursorWithValue,
IDBDatabase,
IDBFactory,
IDBIndex,
IDBKeyRange,
IDBObjectStore,
IDBOpenDBRequest,
IDBRequest,
IDBTransaction,
IDBVersionChangeEvent,
} from "fake-indexeddb";
// The rest is the same as above.
`
Like any imported variable, you can rename it if you want, for instance if you don't want to conflict with built-in IndexedDB variables:
`js`
import {
indexedDB as fakeIndexedDB,
} from "fake-indexeddb";
As of version 4, fake-indexeddb includes TypeScript types. As you can see in types.d.ts, it's just using TypeScript's built-in IndexedDB types, rather than generating types from the fake-indexeddb code base. The reason I did this is for compatibility with your application code that may already be using TypeScript's IndexedDB types, so if I used something different for fake-indexeddb, it could lead to spurious type errors. In theory this could lead to other errors if there are differences between Typescript's IndexedDB types and fake-indexeddb's API, but currently I'm not aware of any difference. See issue #23 for more discussion.
If you import fake-indexeddb/auto before importing dexie, it should work:
`js
import "fake-indexeddb/auto";
import Dexie from "dexie";
const db = new Dexie("MyDatabase");
`
The same likely holds true for other IndexedDB API wrappers like idb.
Alternatively, if you don't want to modify the global scope, then you need to explicitly pass the objects to Dexie:
`js
import Dexie from "dexie";
import { indexedDB, IDBKeyRange } from "fake-indexeddb";
const db = new Dexie("MyDatabase", { indexedDB: indexedDB, IDBKeyRange: IDBKeyRange });
`
To use fake-indexeddb in a single Jest test suite, require fake-indexeddb/auto at the beginning of the test
file, as described above.
To use it on all Jest tests without having to include it in each file, add the auto setup script to the setupFiles in your Jest config:
`json`
{
"setupFiles": [
"fake-indexeddb/auto"
]
}
As of version 5, fake-indexeddb no longer includes a structuredClone polyfill. This mostly affects old environments like unsupported versions of Node.js, but it also affects jsdom, which is often used with Jest and other testing frameworks.
There are a few ways you could work around this. You could include your own structuredClone polyfill by installing core-js and importing its polyfill before you use fake-indexeddb:
`js`
import "core-js/stable/structured-clone";
import "fake-indexeddb/auto";
Or, you could manually include the Node.js structuredClone implementation in a jsdom environment:
`js
// FixJSDOMEnvironment.ts
import JSDOMEnvironment from 'jest-environment-jsdom';
// https://github.com/facebook/jest/blob/v29.4.3/website/versioned_docs/version-29.4/Configuration.md#testenvironment-string
export default class FixJSDOMEnvironment extends JSDOMEnvironment {
constructor(...args: ConstructorParameters
super(...args);
// FIXME https://github.com/jsdom/jsdom/issues/3363
this.global.structuredClone = structuredClone;
}
}
`
`js
// jest.config.js
/* @type {import('jest').Config} /
const config = {
testEnvironment: './FixJSDOMEnvironment.ts',
};
module.exports = config;
`
Hopefully a future version of jsdom will no longer require these workarounds.
If you are keeping your tests completely isolated you might want to "reset" the state of the mocked indexedDB. You can do this by creating a new instance of IDBFactory, which lets you have a totally fresh start.
`js
import "fake-indexeddb/auto";
import { IDBFactory } from "fake-indexeddb";
// Whenever you want a fresh indexedDB
indexedDB = new IDBFactory();
`
An IDBDatabase will fire a "close" event when closed for abnormal reasons, such as the user manually deleting databases in DevTools. If you want to simulate this event for test coverage, you can use forceCloseDatabase():
`js
import { forceCloseDatabase } from "fake-indexeddb";
db.addEventListener("close", () => {
console.log("Forcibly closed!");
});
forceCloseDatabase(db); // invokes the event listener
`
Note that forceCloseDatabase() is not a standard IndexedDB API and is unique to fake-indexeddb.
PhantomJS (and other really old environments) are missing tons of modern JavaScript features. In fact, that may be why you use fake-indexeddb in such an environment! Prior to v3.0.0, fake-indexeddb imported core-js and automatically applied its polyfills. However, since most fake-indexeddb users are not using really old environments, I got rid of that runtime dependency in v3.0.0. To work around that, you can import core-js yourself before you import fake-indexeddb, like:
`js`
import "core-js/stable";
import "fake-indexeddb/auto";
Here's a comparison of fake-indexeddb and real browser IndexedDB implementations on the Web Platform Tests IndexedDB suite as of November 7, 2025:
| Implementation | Version | Passed | % |
| --- | --- | --- | --- |
| Chrome | 144.0.7514.0 | 1651 | 99.9% |
| Firefox | 146.0a1 | 1498 | 90.6% |
| Safari | 231 preview | 1497 | 90.6% |
| Ladybird | 1.0-cde3941d9f | 1426 | 86.3% |
| fake-indexeddb | 6.2.5 | 1369 | 82.8% |
Keep in mind that these tests include a lot of edge cases (such as rare error conditions), so even hitting ~40% likely means that the core IndexedDB functionality is covered. Your app will probably work fine.
Also note that, for a fair comparison with browsers, these results omit some tests that aren't relevant to Node.js such as web workers and cross-origin isolation. When testing fake-indexeddb, some polyfills are used to simulate a browser environment, such as File and location.
> [!NOTE]
> To see how these test results are generated, see update-browser-wpt-results.js and run-all.js`.
1. Use as a mock database in unit tests.
2. Use the same API in Node.js and in the browser.
3. Support IndexedDB in old or crappy browsers.
4. Somehow use it within a caching layer on top of IndexedDB in the browser, since IndexedDB can be kind of slow.
5. Abstract the core database functions out, so what is left is a shell that allows the IndexedDB API to easily sit on top of many different backends.
6. Serve as a playground for experimenting with IndexedDB.
Apache 2.0