Not browsers being smart as much as this is being explicitly mentioned in the RFC - updating bookmarks and other references is kind of the point of 301 Moved Permanently. To quote from RFC 7231:<p><pre><code>   The 301 (Moved Permanently) status code indicates that the target
   resource has been assigned a new permanent URI and any future
   references to this resource ought to use one of the enclosed URIs.
   Clients with link-editing capabilities ought to automatically re-link
   references to the effective request URI to one or more of the new
   references sent by the server, where possible.
</code></pre>
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