stale-while-revalidate has a default time?

[shchoon]

I would to set stale-while-revlidate, but, in NextJs offical Docs, part of next.config -> headers -> Cache-control said 'you cannot set headers in next.config.js'. Then 'stale-while-revlidate' has a default time??

[icyJoseph]

You cannot set Cache-Control headers in next.config.js for these assets.

The assets it talks about, are so called, truly immutable files, which contents are hashed, and the hash is used to name the file. So, those can't be set.

Could you try to explain what is it you are trying to do? stale-while-revalidate, on which assets? There's a expireTime option in the config as well, but I am not sure that's what you need, https://nextjs.org/docs/app/api-reference/config/next-config-js/expireTime

[shchoon]

Thank you for your answer😊
Now, I am trying revalidate on time based. I set revalidate time to 60s on my api request, so when i request page, good work revalidate. Then i have a fresh data on my cache by revalidate. If i request page for route, broswer refer stale cache data during 30s. After 30s on revalidate, if i request the page for route, brower refer fresh cache. Even though I did not set 'stale-while-revalidate', it takes 30s to refer fresh cache data. This is why I am wondering stale-while-revalidate has default time.

[icyJoseph]

Aha, which Next.js version do you have? https://nextjs.org/docs/app/api-reference/config/next-config-js/staleTimes seems to be what you want to read up.

In version 15, they changed the dynamic stale time, from 30 seconds to 0.

This was also documented in the caching and routing deep dive, last I checked anyway, https://nextjs.org/docs/app/building-your-application/caching#duration-3

[shchoon]

Now, I have version 14. After referring to your answer, the problem is solved. In version 14, dynamic stale time is 30s by default. I did configure dynamic stale time to 10s, then after 10s of revlidate, browser refer to refreshed cache data on route request. Thank to you, i wa able to solve the problem 👍.
And i have a question. I thought ISR was same concept as revalidation in the app router, so I understood that revalidated page should be statically generated. However, based on your answer and actually applying it, revlidation seems to be dynamic generation. Is revlidation used in app router same concept as ISR?

[icyJoseph]

Yes it is, I wonder if your page is being opted-in to dynamic rendering? When you build your app, there is a summary of what type of page is page is, are your pages having the correct output?

Also the staleTimes thing, is for client side routing caching.

Please don't forget to mark as answered if you are satisfied.

[shchoon]

It is summary at build. Now, i am confused about whether rendered page of revliadation is dynamically rendered. At the initial build, page has static rendering. And after revalidation, it requests data and changes cache data to refresh data, then builds new HTML based on fresh data.
In this proecess, I thought getting fresh data for revalidation is dynamic and build HTML is static. So, I am confused about whether rendering for revlidation is dynamic or static.