You can use pixivFANBOX on PCs, smartphones or tablet device.
It does not support to feature phones.
Recommended browser (on PC)
Google Chrome (latest version)
https://www.google.com/chrome/
Safari (latest version)
https://www.apple.com/safari/
Also, pixivFANBOX does not support to Internet Explorer.
Please use Microsoft Edge or use the above recommended browsers.
Recommended browser (on Smartphone)
iOS
Safari (latest version)
Android
Google Chrome (latest version)
Moreover, operation is not guaranteed for Android browser.
Please use Google Chrome.