Add note about Clear-Site-Data in Chrome 138

Author: csswizardry

_posts/2019-03-04-cache-control-for-civilians.md

@@ -2,6 +2,7 @@
 layout: post
 title: "Cache-Control for Civilians"
 date: 2019-03-04 01:21:39
+last_modified_at: 2025-06-05
 categories: Web Development
 meta: "What does Cache-Control really do? In basic terms? Let’s find out!"
 ---
@@ -453,7 +454,11 @@ Opera.
 
 **Tip:** There are a number of directives that `Clear-Site-Data` will accept:
 `"cookies"`, `"storage"`, `"executionContexts"`, and `"*"` (which, naturally,
-means ‘all of the above’).
+means ‘all of the above’), and starting with [Chrome
+138](https://developer.chrome.com/blog/chrome-138-beta#speculation_rules_add_prefetchcache_and_prerendercache_to_clear-site-data_header),
+support for the `prefetchCache` and `prerenderCache` directives is added to help
+you clear caches populated by [Speculation
+Rules](/2024/12/a-layered-approach-to-speculation-rules/).
 
 - - -
 

_posts/2023-10-02-clear-cache-on-customer-device.md

@@ -2,6 +2,7 @@
 layout: post
 title: "How to Clear Cache and Cookies on a Customer’s Device"
 date: 2023-10-02 15:30:49
+last_modified_at: 2025-06-05
 categories: Web Development
 main: "https://csswizardry.com/wp-content/uploads/2023/10/clear-site-data.png?1"
 meta: "There’s a super quick and easy way to clear cache on your customers’ devices. Are you using it yet?"
@@ -84,6 +85,20 @@ will notice performance degradations. While ever the header is live, you will be
 constantly evicting users’ caches, effectively disabling caching for your site
 the whole time. Tread carefully!
 
+## <ins datetime="2025-06-05">Clearing Speculation Rules’ Cache</ins>
+
+Starting in [Chrome
+138](https://developer.chrome.com/blog/chrome-138-beta#speculation_rules_add_prefetchcache_and_prerendercache_to_clear-site-data_header),
+`Clear-Site-Data` is being extended by two additional directives that will empty
+the prefetch and prerender caches respectively:
+
+```http
+Clear-Site-Data: "prefetchCache", "prerenderCache"
+```
+
+This will be particularly useful in cases you may have misconfigured your
+[Speculation Rules](/2024/12/a-layered-approach-to-speculation-rules/).
+
 ## Clearing Cache on iOS
 
 Unfortunately, `Clear-Site-Data` is not supported by Safari, and as all browsers

_posts/2024-12-02-a-layered-approach-to-speculation-rules.md

@@ -2,6 +2,7 @@
 layout: post
 title: "A Layered Approach to Speculation Rules"
 date: 2024-12-02 00:01:56
+last_modified_at: 2025-06-05
 categories: Web Development
 main: "https://csswizardry.com/wp-content/uploads/2024/12/speculation-rules-poster.jpg"
 meta: "The new Speculation Rules API is incredibly powerful, but we can do so much more! By taking a layered, opt-in approach, we can add more progressive and effective functionality."
@@ -451,6 +452,16 @@ I guess my point after all of this is that I think this is quite an elegant
 pattern and I’m quite happy with myself. If you’d like to be happy with me, too,
 I’m taking on [new clients for 2025](/services/).
 
+## <ins datetime="2025-06-05">Clearing Speculation Rules’ Cache With `Clear-Site-Data`</ins>
+
+In the [upcoming Chrome 138
+release](https://developer.chrome.com/blog/chrome-138-beta#speculation_rules_add_prefetchcache_and_prerendercache_to_clear-site-data_header),
+the [`Clear-Site-Data` HTTP response
+header](/2023/10/clear-cache-on-customer-device/) is being extended to add
+support for both the `prefetchCache` and `prerenderCache` directives. These can
+be used by developers to forcibly purge end-users caches in the event you may
+have incorrectly or misconfigured something in or around your Speculation Rules.
+
 <small>Thanks to [Barry Pollard](https://x.com/tunetheweb) for sense-checks and
 streamlining.</small>