(Updated in 2022/11/14) This addon is still very terribly unstable. I'm living in Taiwan, and network environment is quite speedy when without VPN, but after enabling Surfshark VPN in Firefox, the experience becomes a nightmare: the network often becomes very slow (Even though the servers I selected shows the loading are quite low, < 25%), or unexpected disconnection and shows some unreasonable error message (for example, it often shows "your subscription is expired", but my subscription should be expired in 2023/06). Whenever I encounter such problem, what I only can do is restarting Firefox, this is the only addon I'm using with the most ridiculous quality.

If you rate 1 star to this addon, no matter how detailed is your issue description in this review, they always reply and ask you to contact their supporter via live chat or email, but if you really do contact with their support, the only thing they are going to do is to merely ask you to reinstall the addon and try again, and you will find nothing improved at all. LOL.

(Updated in 2022/04/14: In 2022/03/01, the reply from developer ask me contact to their Customer Support via Email, and they ask me to reinstalling the addon. So I reinstalled, however this doesn't solve the problem at all. It just logged out immediately when I click on addon's icon in 2022/04/14. Ridiculous. ) This addon may suitable for some unimportant tasks such as watching Netflix, BUT this is DEFINITELY NOT SAFE for sensitive data. Because this addon gets red text "error" in the popup UI frequently and cannot work at all until I restart my Firefox, sometime I have to restart my Firefox more than 5 times in a day. // THE TERRIBLY WORST PART IS: sometimes, when mouse hovering on the toolbar icon, it shows colored "connected" so I feel easy to work. But occasionally when I click the toolbar icon... I was astonished to find that I am totally logged-out, without any sign?! (and the toolbar icon became to gray immediately), I even donno when it logged out. What the hell is this stability for a service focused on "Security"? You even cannot make a average-degree stable addon. I have never used any other addon is unstable like half of this one in recent 10 years.