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Correct Speculation Rules HTTP Status code support #35624

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merged 3 commits into from
Aug 28, 2024
Merged

Correct Speculation Rules HTTP Status code support #35624

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8fdbe5e
Correct Speculation Rules HTTP Status code support
tunetheweb Aug 28, 2024
8e2ce7c
Make 204/205 more explicit for prefetch
tunetheweb Aug 28, 2024
3a6cc11
504 - 503
tunetheweb Aug 28, 2024
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4 changes: 3 additions & 1 deletion files/en-us/web/api/speculation_rules_api/index.md
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Expand Up @@ -179,7 +179,9 @@ For prerender:
Sec-Purpose: prefetch;prerender
```

Servers can respond based on this header, for example, to log speculative load requests, return different content, or even prevent speculative loading from happening. If a non-success response code is returned (any HTTP status other than 200 or 304), then the page will not be prefetched/prerendered. This is the easiest way to prevent speculative loading, although it is usually a better approach to allow the prefetch/prerender, and use JavaScript to delay any actions that should only happen when the page is actually viewed.
Servers can respond based on this header, for example, to log speculative load requests, return different content, or even prevent speculative loading from happening. If a non-success response code is returned (any HTTP status other than in the 200-299 range after redirects), then the page will not be prefetched/prerendered. In addition the 204 and 205 status codes also prevent prerendering (but do not prevent prefetch).

Using a non-success code (for example a 504) is the easiest way to prevent speculative loading server-side, although it is usually a better approach to allow the prefetch/prerender, and use JavaScript to delay any actions that should only happen when the page is actually viewed.
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Is 504 intentional here? This comment: WICG/nav-speculation#330 (comment) suggests 503, which seems closer in intent.

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Oh good spot! Fixed.


### JavaScript prefetch detection

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