IndexedDB is a low-level API for client-side storage of significant amounts of structured data, including files/blobs. This API uses indexes to enable high performance searches of this data. While DOM Storage is useful for storing smaller amounts of data, it is less useful for storing larger amounts of structured data. IndexedDB provides a solution. This is the main landing page for MDN's IndexedDB coverage — here we provide links to the full API reference and usage guides, browser support details, and some explanation of key concepts.
Note: IndexedDB API is powerful, but may seem too complicated for simple cases. If you'd prefer a simple API, try libraries such as localForage and dexie.js that make IndexedDB more user-friendly.
Note: Some older browsers don't support IndexedDB but do support WebSQL. One way around this problem is to use an IndexedDB Polyfill or Shim that falls back to WebSQL or even localStorage for non-supporting browsers. The best available polyfill at present is localForage.
Key concepts and usage
IndexedDB is a transactional database system, like an SQL-based RDBMS. However, unlike SQL-based RDBMS, which use fixed-column tables, IndexedDB is a JavaScript-based object-oriented database. IndexedDB lets you store and retrieve objects that are indexed with a key; any objects supported by the structured clone algorithm can be stored. You need to specify the database schema, open a connection to your database, and then retrieve and update data within a series of transactions.
- Read more about the Concepts behind IndexedDB.
- Learn to use IndexedDB asynchronously from first principles with our Using IndexedDB guide.
- Find developer recommendations for making web apps work offline at our Offline Apps page.
Note: Like most web storage solutions, IndexedDB follows a same-origin policy. So while you can access stored data within a domain, you cannot access data across different domains.
Synchronous and asynchronous
Operations performed using IndexedDB are done asynchronously, so as not to block applications. IndexedDB originally included both synchronous and asynchronous APIs. The synchronous API was intended for use only with Web Workers, but was removed from the spec because it was unclear whether it was needed. However, the synchronous API may be reintroduced if there is enough demand from web developers.
Storage limits and eviction criteria
There are a number of web technologies that store data of one kind or another on the client side (i.e. on your local disk). IndexedDB is the most commonly talked about one. The process by which the browser works out how much space to allocate to web data storage and what to delete when that limit is reached is not simple, and differs between browsers. Browser storage limits and eviction criteria attempts to explain how this works, at least in the case of Firefox.
Interfaces
To get access to a database, call open() on the indexedDB attribute of a window object. This method returns an IDBRequest object; asynchronous operations communicate to the calling application by firing events on IDBRequest objects.
Connecting to a database
IDBEnvironment- Provides access to IndexedDB functionality. It is implemented by the
windowandworkerobjects. IDBFactory- Provides access to a database. This is the interface implemented by the global object
indexedDBand is therefore the entry point for the API. IDBOpenDBRequest- Represents a request to open a database.
IDBDatabase- Represents a connection to a database. It's the only way to get a transaction on the database.
- Retrieving and modifying data
IDBTransaction- Represents a transaction. You create a transaction on a database, specify the scope (such as which object stores you want to access), and determine the kind of access (read only or readwrite) that you want.
IDBRequest- Generic interface that handles database requests and provides access to results.
IDBObjectStore- Represents an object store that allows access to a set of data in an IndexedDB database, looked up via primary key.
IDBIndex- Also allows access to a subset of data in an IndexedDB database, but uses an index to retrieve the record(s) rather than the primary key. This is sometimes faster than using
IDBObjectStore. IDBCursor- Iterates over object stores and indexes.
IDBCursorWithValue- Iterates over object stores and indexes and returns the cursor's current value.
IDBKeyRange- Defines a key range that can be used to retrieve data from a database in a certain range.
IDBLocaleAwareKeyRange- Defines a key range that can be used to retrieve data from a database in a certain range, sorted according to the rules of the locale specified for a certain index (see
createIndex()'s optionalParameters.).
Custom event interfaces
This specification fires events with the following custom interface:
IDBVersionChangeEvent- The
IDBVersionChangeEventinterface indicates that the version of the database has changed, as the result of anIDBOpenDBRequest.onupgradeneededevent handler function.
Obsolete interfaces
An early version of the specification also defined these now removed interfaces. They are still documented in case you need to update previously written code:
IDBVersionChangeRequest- Represents a request to change the version of a database. The way to change the version of the database has since changed (by calling
IDBFactory.openwithout also callingIDBDatabase.setVersion), and the interfaceIDBOpenDBRequestnow has the functionality of the removedIDBVersionChangeRequest. IDBDatabaseException- Represents exception conditions that can be encountered while performing database operations.
IDBTransactionSync- Sync version of
IDBTransaction. IDBObjectStoreSync- Sync version of
IDBObjectStore. IDBIndexSync- Sync version of
IDBIndex. IDBFactorySync- Sync version of
IDBFactory. IDBEnvironmentSync- Sync version of
IDBEnvironment. IDBDatabaseSync- Sync version of
IDBDatabase. IDBCursorSync- Sync version of
IDBCursor.
Examples
- eLibri: A powerful library and eBook reader application, written by Marco Castelluccio, winner of the IndexedDB Mozilla DevDerby.
- To-do Notifications (view example live): The reference application for the examples in the reference docs.
- Storing images and files in IndexedDB
Specifications
| Specification | Status | Comment |
|---|---|---|
| Indexed Database API | Recommendation | Initial definition |
Browser compatibility
| Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
|---|---|---|---|---|---|
| Basic support |
23.0 webkit |
10.0 (10.0) moz 16.0 (16.0) |
10, partial | 15 | 7.1 |
| Available in workers | (Yes) | 37.0 (37.0)[1] | No support[3] | (Yes) | No support[4] |
IDBLocaleAwareKeyRange |
No support | 43.0 (43.0)[2] | No support | No support | No support |
| Feature | Android | Firefox Mobile (Gecko) | Firefox OS | IE Phone | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|---|
| Basic support | 4.4 | 22.0 (22.0) | 1.0.1 | 10 | 22 | 8 |
| Available in workers | (Yes) | 37.0 (37.0)[1] | (Yes) | ? | (Yes) | ? |
IDBLocaleAwareKeyRange |
No support | 43.0 (43.0)[2] | 2.5[2] | No support | No support | No support |
- [1]
IDBCursorWithValueis not available in workers until Gecko 42.0 (Firefox 42.0 / Thunderbird 42.0 / SeaMonkey 2.39). - [2] This feature is currently hidden behind a flag — to enable it and experiment, go to about:config and enable dom.indexedDB.experimental.
- [3] IE/Edge bug #866495
- [4] WebKit bug #149953
See also
- localForage: A Polyfill providing a simple name:value syntax for client-side data storage, which uses IndexedDB in the background, but falls back to WebSQL and then localStorage in browsers that don't support IndexedDB.
- dexie.js: A wrapper for IndexedDB that allows much faster code development via nice, simple syntax.