Mozilla 的提案「HTTP Immutable Responses」

狀態已經是 Category: Standards Track 了，RFC 8246 的「HTTP Immutable Responses」：

The immutable HTTP response Cache-Control extension allows servers to identify resources that will not be updated during their freshness lifetime. This ensures that a client never needs to revalidate a cached fresh resource to be certain it has not been modified.

對 Cache-Control 介紹了 immutable，像是這樣：

Cache-Control: max-age=31536000, immutable

依照 MDN 上的資料 (Cache-Control - HTTP | MDN)，目前只有 Edge 與 Firefox 支援，不過既然成為標準了，後續其他瀏覽器應該都會支援 (吧)：