Firefox RCWN (race cache with network)

September 3, 2019

Sometimes in the Firefox devtools network tab you might find a request that is flagges as "raced".

That is because Firefox has implemented a "RCWN" (race cache with network) strategy where it'll try to fetch assets that are already cached from the network when IO is slow on the device and re-issuing the network request will actually be faster than reading the file from disk.

You can see stats at: about:networking#rcwn