I have found what I assume is Rekonq's cache but none of the files have extensions and I can't open them. The file sizes seem similar to the normal files I would expect in Opera which saves cache files in normal formats. I have tried guessing at file types and adding the appropriate extension but that didn't help.

What format does rekonq use to store files in the cache and is it possible to convert them back to standard formats?

thanks

Assuming Rekonq is using the cache located at /var/tmp/kdecache-$USER/http/ then it likely isn't possible to extract the files without a custom tool. I say this because the files (from what I can tell) include the headers and other metadata sent by the web server from which Rekonq downloaded it.