The current status of downloading images from cache

[eight04]

Since Firefox and Chrome both implemented cache partitioning, extensions can't download images from cache anymore.

Firefox:

• cache partitioning causes web page saving extensions to waste more time and data
• Allow extensions to specify request context in the browser.downloads.download API
• Enable extensions to send network requests (fetch) with a specific cookieStoreId (container tab context)

Chrome:

• cache partitioning causes web page saving extensions to waste more time and data - which is marked as wontfix 😕

  I don't believe allowing extensions to look in any cache partition or even in just the current page's cache partition would be feasible since that would allow malicious extensions to be able to infer if a resource is cached or not by the user.

Test suite

https://github.com/eight04/webext-hit-the-cache

Firefox workaround

You can turn off cache partitioning by setting privacy.partition.network_state to false in about:config.

Chrome workaround

Turn off this feature via the CLI option: --disable-features=SplitCacheByNetworkIsolationKey.

[michael-ziedalski]

Hi! As a long-time Firefox user who all too-often leaves image tabs open until the hosting websites remove them, I found this addon hoping it would be able to directly access the cache.

I checked my about:config, and privacy.partition.network_state is already set to false, so that workaround does not work. Could something be interfering with the workaround?

[eight04]

leaves image tabs open until the hosting websites remove them

The cache might already expire in this case. You can visit about:cache and see if the image is still there.

[michael-ziedalski]

In that case, is there anywhere in Firefox's documentation where the images are stored, since it seems the images are still definitely being held somewhere.

[eight04]

In that case, is there anywhere in Firefox's documentation where the images are stored, since it seems the images are still definitely being held somewhere.

IDK. Why do you think the image is still held somewhere?