Burner wallets are non-custodial wallets that store a user's private key in the browser’s local storage. A change made by Apple to Safari’s Webkit engine meant to enhance user privacy may jeopardize this model.
This change will cap “the expiry of client-side cookies to seven days”. This implies that burner wallets will be destroyed after that short period. Although burner wallets were never intended for long-term storage of cryptocurrency, some users choose not to follow this rule.
Exception to the rule
Fortunately, there is one exception to this change — adding an app to the home screen. The blog post announcing the change states:
“The seven-day cap on script-writable storage is gated on ‘after seven days of Safari use without user interaction on the site’. That is the case in Safari. Web applications added to the home screen are not part of Safari and thus have their own counter of days of use. Their days of use will match actual use of the web application which resets the timer. We do not expect the first-party in such a web application to have its website data deleted.”
Unfortunately, adding a burner wallet to the home screen is no easy task. Former Google software engineer David Mihal wrote a blog examining the changes, and noted:
“Unfortunately, there’s no ‘easy’ way to prompt a user to add a website to their home screen, users must find the button hidden inside Safari’s ‘share’ panel. Future Burner Wallets will likely display warnings to Safari users, prompting them to add the wallet to the home screen & secure their funds.”
Back in 2017 there were 720 million iPhones in use around the world, it is unknown what percentage of iPhone owners use Safari-based burner wallets.