Automatic Revalidation

Revalidate on Focus

When you re-focus a page or switch between tabs, SWR automatically revalidates data.

This can be useful to immediately synchronize to the latest state. This is helpful for refreshing data in scenarios like stale mobile tabs, or laptops that went to sleep.

This feature is enabled by default. You can disable it via the revalidateOnFocus option.

Revalidate on Interval

In many cases, data changes because of multiple devices, multiple users, multiple tabs. How can we over time update the data on screen?

SWR will give you the option to automatically refetch data. It’s smart which means refetching will only happen if the component associated with the hook is on screen.

You can enable it by setting a refreshInterval value:

useSWR('/api/todos', fetcher, { refreshInterval: 1000 })

There’re also options such as refreshWhenHidden and refreshWhenOffline. Both are disabled by default so SWR won’t fetch when the webpage is not on screen, or there’s no network connection.

Revalidate on Reconnect

It’s useful to also revalidate when the user is back online. This scenario happens a lot when the user unlocks their computer, but the internet is not yet connected at the same moment.

To make sure the data is always up-to-date, SWR automatically revalidates when network recovers.

This feature is enabled by default. You can disable it via the revalidateOnReconnect option.

Disable Automatic Revalidations

If the resource is immutable, that will never change if we revalidate again, we can disable all kinds of automatic revalidations for it.

Since version 1.0, SWR provides a helper hook useSWRImmutable to mark the resource as immutable:

import useSWRImmutable from 'swr/immutable'
 
// ...
useSWRImmutable(key, fetcher, options)

It has the same API interface as the normal useSWR hook. You can also do the same thing by disable the following revalidation options:

useSWR(key, fetcher, {
  revalidateIfStale: false,
  revalidateOnFocus: false,
  revalidateOnReconnect: false
})
 
// equivalent to
useSWRImmutable(key, fetcher)

The revalidateIfStale controls if SWR should revalidate when it mounts and there is stale data.

These 2 hooks above do the exact same thing. Once the data is cached, they will never request it again.