Send an email saying "you're about to be charged, click here to cancel your membership"

Exactly. This is what I want all my subscriptions to do.

In UPI (I know I know...) there is an autopay system. Your single UPI app has a single page with all your subscriptions. You can cancel or do whatever there and it's all handled in one place. My openai, streaming services, youtube premium, amazon prime, everything is on there. It gives me notifications before a charge is about to occur. No dark patterns.

This is the standard I expect.

Since credit cards don't provide a centralised thing like that, it's up to the SaaS provider to give the equivalent experience.

Cancelling should be _exactly_ as easy as signing up. If that means your MAU doesn't increase as fast, maybe you have a shit product. Case in point: amazon prime can have cancel buttons littered all across every page and I'm still not gonna cancel it.

Here's the simplest implementation: Few days before and on the day of charging, some infobox on the app's most attention-requiring screen, and an email telling me I'm gonna be charged. In all those communications, the main CTA should be a cancel button, that without further ado, let's me confirm and cancel the thing.

Anything even one step more complicated is a dark pattern.

Someone downthread mentioned - what if they want to change their subscription level instead of cancelling? In that case, two CTAs: change plan, and cancel. Both equally sized and right next to each other with good color contrast - important! None of that greyed out cancel button bullshit.