whatwg · pmeenan · Jun 8, 2026 · Jun 8, 2026 · Jun 8, 2026 · Jun 8, 2026
diff --git a/fetch.bs b/fetch.bs
@@ -16,12 +16,19 @@ Translate IDs: typedefdef-bodyinit bodyinit,dictdef-requestinit requestinit,type
 urlPrefix:https://httpwg.org/specs/rfc5861.html#;type:dfn;spec:stale-while-revalidate
     url:n-the-stale-while-revalidate-cache-control-extension;text:stale-while-revalidate lifetime
 
+urlPrefix:https://httpwg.org/specs/rfc9842.html#;type:dfn;spec:rfc9842
+    url:use-as-dictionary;text:Use-As-Dictionary
+    url:available-dictionary;text:Available-Dictionary
+    url:dictionary-id;text:Dictionary-ID
+    url:rfc.section.2.2;text:finding the best matching dictionary
+
 urlPrefix:https://httpwg.org/specs/rfc9651.html#;type:dfn;spec:rfc9651
     url:rfc.section.2;text:structured field value
     url:text-serialize;text:serializing structured fields
     url:text-parse;text:parsing structured fields
     url:;text:structured header
     url:token;text:structured field token
+    url:parse-bare-item;text:bare item
 
 urlPrefix:https://httpwg.org/specs/rfc9110.html#;type:dfn;spec:http
     url:method.overview;text:method
@@ -67,6 +74,11 @@ urlPrefix:https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-layered-cooki
     url:name-serialize-cookies;text:serialize cookies
     url:name-garbage-collect-cookies;text:garbage collect cookies
 
+urlPrefix:https://urlpattern.spec.whatwg.org/#;type:dfn;spec:urlpattern
+    url:url-pattern-create;text:creating a URL pattern
+    url:url-pattern-has-regexp-groups;text:has regexp groups
+
+
 urlPrefix:https://www.rfc-editor.org/rfc/rfc6454;type:dfn;spec:RFC6454
     url:section-7.1;text:serialized-origin
 </pre>
@@ -1822,6 +1834,7 @@ device to assist defining CSP and Mixed Content. It is not exposed to JavaScript
 the empty string,
 "<code>audio</code>",
 "<code>audioworklet</code>",
+"<code>compression-dictionary</code>",
 "<code>document</code>",
 "<code>embed</code>",
 "<code>font</code>",
@@ -1878,7 +1891,7 @@ not always relevant and might require different behavior.
    <th>CSP directive
    <th>Features
   <tr>
-   <td rowspan=22>""
+   <td rowspan=23>""
    <td>"<code>report</code>"
    <td rowspan=2>&mdash;
    <td>CSP, NEL reports.
@@ -1970,6 +1983,10 @@ not always relevant and might require different behavior.
    <td>"<code>video</code>"
    <td><code>media-src</code>
    <td>HTML's <code>&lt;video></code> element
+  <tr>
+   <td>"<code>compression-dictionary</code>"
+   <td><code>connect-src</code>
+   <td>HTML's <code>&lt;link rel=compression-dictionary></code>
   <tr>
    <td>"<code>download</code>"
    <td>""
@@ -2326,9 +2343,10 @@ When a request is [=request/cloned=], the created request gets a unique
 
 <p>A <dfn export>subresource request</dfn> is a <a for=/>request</a>
 whose <a for=request>destination</a> is "<code>audio</code>", "<code>audioworklet</code>",
-"<code>font</code>", "<code>image</code>", "<code>json</code>", "<code>manifest</code>",
-"<code>paintworklet</code>", "<code>script</code>", "<code>style</code>", "<code>text</code>",
-"<code>track</code>", "<code>video</code>", "<code>xslt</code>", or the empty string.
+"<code>compression-dictionary</code>", "<code>font</code>", "<code>image</code>",
+"<code>json</code>", "<code>manifest</code>", "<code>paintworklet</code>", "<code>script</code>",
+"<code>style</code>", "<code>text</code>", "<code>track</code>", "<code>video</code>",
+"<code>xslt</code>", or the empty string.
 
 <p>A <dfn export>non-subresource request</dfn> is a <a for=/>request</a>
 whose <a for=request>destination</a> is "<code>document</code>", "<code>embed</code>",
@@ -3326,6 +3344,22 @@ or an <a>implementation-defined</a> value.
 </div>
 
 
+<h3 id=compression-dictionary-cache-partitions>Compression-dictionary cache partitions</h3>
+
+<div algorithm>
+<p>To <dfn>determine the compression-dictionary cache partition</dfn>, given a <a for=/>request</a> <var>request</var>:
+
+<ol>
+ <li><p>Let <var>key</var> be the result of <a for=request>determining the network partition key</a>
+ given <var>request</var>.
+
+ <li><p>If <var>key</var> is null, then return null.
+
+ <li><p>Return the unique compression-dictionary cache associated with <var>key</var>. [[!RFC9842]]
+</ol>
+</div>
+
+
 <h3 id=port-blocking>Port blocking</h3>
 
 <p class=note>New protocols can avoid the need for blocking ports by negotiating the protocol
@@ -6435,8 +6469,9 @@ run these steps:
    <li><p>If <var>httpRequest</var>'s <a for=request>cache mode</a> is
    "<code>only-if-cached</code>", then return a <a>network error</a>.
 
-   <li><p>Let <var>forwardResponse</var> be the result of running <a>HTTP-network fetch</a> given
-   <var>httpFetchParams</var>, <var>includeCredentials</var>, and <var>isNewConnectionFetch</var>.
+   <li><p>Let <var>forwardResponse</var> be the result of running
+   <a>HTTP-network compression-dictionary fetch</a> given <var>httpFetchParams</var>,
+   <var>includeCredentials</var>, and <var>isNewConnectionFetch</var>.
 
    <li><p>If <var>httpRequest</var>'s <a for=request>method</a> is <a>unsafe</a> and
    <var>forwardResponse</var>'s <a for=response>status</a> is in the range 200 to 399, inclusive,
@@ -6585,12 +6620,152 @@ run these steps:
  <li><p>If <var>isAuthenticationFetch</var> is true, then create an <a>authentication entry</a> for
  <var>request</var> and the given realm.
 
+ <li>
+  <p>If <var>request</var>'s <a for=request>response tainting</a> is not "<code>opaque</code>",
+  <var>request</var>'s <a for=request>client</a> is a <a>secure context</a>, and
+  <var>response</var>'s <a for=response>header list</a> <a for="header list">contains</a>
+  <a><code>Use-As-Dictionary</code></a>:
+  <!-- This is defined in [[!RFC9842]] -->
+
+  <ol>
+   <li><p>Let <var>dictionaryValue</var> be the result of
+   <a for="header list">getting a structured field value</a> given <a><code>Use-As-Dictionary</code></a>,
+   "<code>dictionary</code>", and <var>response</var>'s <a for=response>header list</a>.
+
+   <li><p>If <var>dictionaryValue</var> is null or <var>dictionaryValue</var>["<code>match</code>"]
+   does not <a for=map>exist</a>, then return <var>response</var>.
+
+   <li><p>If <var>dictionaryValue</var>["<code>type</code>"] <a for=map>exists</a> and its
+   <a>bare item</a> is not an <a>implementation-defined</a> supported dictionary type, then return
+   <var>response</var>.
+
+   <li><p>If <var>dictionaryValue</var>["<code>id</code>"] <a for=map>exists</a> and its
+   <a>bare item</a>'s <a for=string>length</a> is greater than 1024, then return
+   <var>response</var>.
+
+   <li>
+    <p>If <var>dictionaryValue</var>["<code>match-dest</code>"] <a for=map>exists</a>:
+
+    <ol>
+     <li><p>Let <var>matchDestList</var> be <var>dictionaryValue</var>["<code>match-dest</code>"][0].
+
+     <li><p>For each <var>dest</var> of <var>matchDestList</var>: if <var>dest</var>'s <a>bare item</a>
+     is not a <a for=request>destination</a> supported by the user agent, then remove <var>dest</var>
+     from <var>matchDestList</var>.
+
+     <li><p>If <var>matchDestList</var> is empty, then return <var>response</var>.
+    </ol>
+
+   <li><p>Let <var>compressionDictionaryCache</var> be the result of
+   <a>determining the compression-dictionary cache partition</a> given <var>request</var>.
+
+   <li><p>If <var>compressionDictionaryCache</var> is null, then return <var>response</var>.
+
+   <li><p>Let <var>pattern</var> be the result of
+   <a for=/>creating a URL pattern</a> given the <a>bare item</a> of <var>dictionaryValue</var>["<code>match</code>"],
+   the <a lt="URL serializer">serialization</a> of <var>request</var>'s <a for=request>current URL</a>,
+   and an empty map. If this throws an exception, then return <var>response</var>.
+
+   <li><p>If <var>pattern</var> is failure or <var>pattern</var> <a for=/>has regexp groups</a>,
+   then return <var>response</var>.
+
+   <li><p>Let <var>expirationTime</var> be the time at which the <var>response</var> becomes
+   a <a>stale response</a>.
+
+   <li><p>If <var>expirationTime</var> is not in the future, then return <var>response</var>.
+
+   <li><p>Store <var>response</var> in <var>compressionDictionaryCache</var> with its associated
+   <var>pattern</var>, <var>dictionaryValue</var>, and <var>expirationTime</var>.
+  </ol>
+
  <li><p>Return <var>response</var>. <span class=note>Typically <var>response</var>'s
  <a for=response>body</a>'s <a for=body>stream</a> is still being enqueued to after
  returning.</span>
 </ol>
 </div>
 
+<h3 id=http-network-compression-dictionary-fetch>HTTP-network compression-dictionary fetch</h3>
+
+<div algorithm>
+<p>To <dfn id=concept-http-network-compression-dictionary-fetch>HTTP-network compression-dictionary fetch</dfn>,
+given a <a for=/>fetch params</a> <var>fetchParams</var>, an optional boolean
+<var>includeCredentials</var> (default false), and an optional boolean <var>forceNewConnection</var>
+(default false):
+
+<ol>
+ <li><p>Let <var>request</var> be <var>fetchParams</var>'s <a for="fetch params">request</a>.
+
+ <li>
+  <p>Let <var>fallback</var> be the following steps:
+
+  <ol>
+   <li><p>Return the result of running <a>HTTP-network fetch</a> given <var>fetchParams</var>,
+   <var>includeCredentials</var>, and <var>forceNewConnection</var>.
+  </ol>
+
+ <li><p>If <var>request</var>'s <a for=request>mode</a> is "<code>no-cors</code>", then return the
+ result of running <var>fallback</var>.
+
+ <li><p>If the user agent is configured to block cookies for <var>request</var>, then return the
+ result of running <var>fallback</var>.
+
+ <li><p>If <var>request</var>'s <a for=request>client</a> is not a <a>secure context</a>, then return the
+ result of running <var>fallback</var>.
+
+ <li><p>Let <var>compressionDictionaryCache</var> be the result of
+ <a>determining the compression-dictionary cache partition</a> given <var>request</var>.
+
+ <li><p>If <var>compressionDictionaryCache</var> is null, then return the result of running
+ <var>fallback</var>.
+
+ <li><p>Let <var>bestMatch</var> be the result of <a>finding the best matching dictionary</a> in
+ <var>compressionDictionaryCache</var> for <var>request</var>.
+
+ <li><p>If <var>bestMatch</var> is null, then return the result of running <var>fallback</var>.
+
+ <li><p>Add the <a><code>Available-Dictionary</code></a> and <a><code>Dictionary-ID</code></a>
+ (if applicable) headers to <var>request</var> using <var>bestMatch</var>.
+
+ <li><p><a for="header list">append</a> (`<code>Accept-Encoding</code>`, `<code>dcb</code>`)
+ to <var>request</var>'s <a for=request>header list</a>.
+
+ <li><p><a for="header list">append</a> (`<code>Accept-Encoding</code>`, `<code>dcz</code>`)
+ to <var>request</var>'s <a for=request>header list</a>.
+
+ <li><p>Let <var>response</var> be the result of running <var>fallback</var>.
+
+ <li><p>Let <var>codings</var> be the result of <a>extracting header list values</a> given
+ `<code>Content-Encoding</code>` and <var>response</var>'s <a for=response>header list</a>.
+
+ <li><p>If <var>codings</var> is null or does not contain `<code>dcb</code>` or `<code>dcz</code>`,
+ then return <var>response</var>.
+
+ <li><p>If <var>request</var>'s <a for=request>response tainting</a> is "<code>opaque</code>",
+ then return a <a>network error</a>.
+
+ <li><p>Let <var>availableDictionaryItem</var> be the result of
+ <a for="header list">getting a structured field value</a> given <a><code>Available-Dictionary</code></a>,
+ "<code>item</code>", and <var>request</var>'s <a for=request>header list</a>.
+
+ <li><p>If <var>availableDictionaryItem</var> is null, then return a <a>network error</a>.
+
+ <li><p>Let <var>availableDictionaryHash</var> be the <a>bare item</a> of <var>availableDictionaryItem</var>.
+
+ <li><p>Let <var>newBody</var> be a new <a for=/>body</a> whose <a for=body>stream</a> is the
+ result of transforming <var>response</var>'s <a for=response>body</a>'s <a for=body>stream</a>
+ with an algorithm that verifies that the dictionary hash in the stream matches
+ <var>availableDictionaryHash</var> and decodes the rest of the stream with the applicable
+ algorithm as defined in [[!RFC9842]]. If verification or decoding fails,
+ error the transformed stream.
+
+ <li><p>Set <var>response</var>'s <a for=response>body</a> to <var>newBody</var>.
+
+ <li><p><a for="header list">delete</a> `<code>Content-Encoding</code>` from <var>response</var>'s
+ <a for=response>header list</a>.
+
+ <li><p>Return <var>response</var>.
+</ol>
+</div>
 
 <h3 id=http-network-fetch>HTTP-network fetch</h3>
 
@@ -6662,6 +6837,7 @@ optional boolean <var>forceNewConnection</var> (default false), run these steps:
 
     <ul>
      <li><p>Follow the relevant requirements from HTTP. [[!HTTP]] [[!HTTP-CACHING]]
+     [[!RFC9842]]
 
      <li>
       <p>If <var>request</var>'s <a for=request>body</a> is non-null, and <var>request</var>'s
@@ -8568,7 +8744,7 @@ dictionary RequestInit {
   any window; // can only be set to null
 };
 
-enum RequestDestination { "", "audio", "audioworklet", "document", "embed", "font", "frame", "iframe", "image", "json", "manifest", "object", "paintworklet", "report", "script", "sharedworker", "style", "text", "track", "video", "worker", "xslt" };
+enum RequestDestination { "", "audio", "audioworklet", "compression-dictionary", "document", "embed", "font", "frame", "iframe", "image", "json", "manifest", "object", "paintworklet", "report", "script", "sharedworker", "style", "text", "track", "video", "worker", "xslt" };
 enum RequestMode { "navigate", "same-origin", "no-cors", "cors" };
 enum RequestCredentials { "omit", "same-origin", "include" };
 enum RequestCache { "default", "no-store", "reload", "no-cache", "force-cache", "only-if-cached" };