Traditionally, XKit had 5 megabytes of storage. To ration this, each extension got 150 kilobytes of storage space. Although this was more than enough at first, with extensions like Post Archiver needing more and more data to save, it just is not enough anymore. 

XKit 7.4.0 now lets extensions storage up to 10 megabytes worth of data, which should be enough to store, for example, thousands of posts on the Post Archiver.

If you are still on XKit 7.3.6 or below, first update extensions from XKit Control Panel > Other > Update All and then follow the instructions here. If you are on Chrome, you can wait for Chrome to update XKit.

After updating, the Storage panel under XKit Control Panel > Other should say that you have a version of XKit with unlimited storage.

I’m working on bringing this to the Opera version of XKit. In the meanwhile, please do not sync your non-Opera XKit with an Opera XKit, since it might give out storage errors.

This is still kind of experimental, so if you hit any bugs, please let me know by sending me an ask. Thank you!