SWR stands for "Stale-While-Revalidate," which is a caching strategy used in web applications to improve performance and reduce network latency. It is commonly used in combination with the HTTP Cache-Control header.
When a client makes a request to the server, the server can respond with a cached version of the requested resource, even if it has expired (stale). This allows the client to quickly receive a response without waiting for the server to generate the resource again.
At the same time, the server initiates a background revalidation process to check if the cached version is still valid. If the resource is still valid, the server will respond with a fresh version and update the cache. However, if the resource has changed, the server will send a new version to the client.
SWR can significantly improve the user experience by reducing the perceived loading time of a web application. It allows the client to display a stale (but still valid) version of the resource while simultaneously fetching an updated version in the background.
This strategy is particularly useful for scenarios where the content doesn't change frequently or when immediate accuracy might not be critical, such as displaying news articles, product listings, or social media feeds. However, it may not be suitable for situations that require real-time data or where immediate accuracy is crucial.
SWR is often implemented in libraries or frameworks such as Next.js and React. It simplifies caching and handling of data fetching, making it easier to build optimized and responsive web applications.