Web storage overview

Choosing the right storage for your web app

Selecting the right storage layer has a direct impact on reliability, bandwidth costs, and perceived responsiveness. The decision affects both local device storage and cloud-based services, and a well-chosen caching strategy is a prerequisite for building offline-capable mobile web experiences.

A framework for evaluating storage options

Storage mechanisms can be analyzed along several axes. Understanding these dimensions makes it easier to compare the available APIs and pick the one that fits the problem at hand.

Data model

The internal organization of data determines how easily it can be queried and how well it performs under different access patterns.

• Structured: Data is held in tables with predefined fields, typical of SQL-based systems. This model suits flexible, dynamic queries where the access patterns aren't known in advance. In the browser, IndexedDB is the primary example.
• Key/Value: Unstructured data is indexed by a unique key, enabling constant-time access similar to a hash table. The Cache API in the browser and Apache Cassandra on the server are representative examples.
• Byte Streams: Data is treated as a variable-length, opaque string of bytes, leaving all internal structure to the application. This fits file systems and hierarchically organized cloud storage services.

Persistence scope

How long data survives depends on the scope over which a storage mechanism retains it.

• Session persistence: Data lasts only as long as the active tab or web session. The Session Storage API is an example.
• Device persistence: Data survives across sessions and window closures on the same device. The Cache API demonstrates this scope.
• Global persistence: Data remains available across sessions and devices, such as with Google Cloud Storage.

Browser support and standards

Standardized, well-established APIs should be favored over custom or proprietary interfaces. They tend to have longer lifespans, broader support, and richer documentation and community resources.

Transactional guarantees

For many domains it's critical that a group of related operations succeed or fail as a unit. Traditional database transaction support may be unnecessary in simple cases but is essential when data integrity depends on atomic updates.

Synchronous versus asynchronous

Blocking storage requests stall the active thread until completion. In the browser this is especially harmful because the storage request competes with the UI on the main thread. Asynchronous APIs are strongly preferred for performance reasons.

Inspecting storage in Chrome DevTools

Chrome DevTools provides inspection and debugging support for several storage APIs. The following tools are covered in the documentation:

• Local Storage
• Session Storage
• Cookies
• Cache
• IndexedDB

For apps that rely on multiple storage mechanisms simultaneously, the Clear Storage feature can flush several stores at once with a single action, which is also useful for wiping service workers, databases, and caches together.

Further reading

Additional detail on browser-side storage engineering is available in the resources on Storage for the web and the Cache API introduction.