Dear WT,

The perennial discussion about ways to provide logged-out users with persistent customization of their reading experience in the browser has cropped up again in the context of the pending deployment of Vector 2022.

Can a cookie-based width toggle https://en.wikipedia.org/wiki/Wikipedia:Requests_for_comment/Deployment_of_Vector_(2022)#Alt_proposal:_gradual_changeover_+_width_toggle be offered without splitting the cache or otherwise making the toggler regret their tog?

The answers currently range from "*shouldn't be very complicated or hacky, just toggling a class*..." and "*can be delivered to logged-out users on top of the cached parser output*.." to "*impossible*".

Could someone clarify the challenges and costs of trying to toggle css classes in this way?

Warmly, SJ