I have 15.6 stable installed and when opening the Stripe test page I receive an error in Firefox (“Either your browser does not support the Payment Request API, or you do not have a saved payment method.”)

iOS 16 beta apparently provides the framework updates necessary for third-party iOS App Store browsers to use it. So you won’t be able to use it on 15.X unless they backport, which is unlikely.

Stripe's demo doesn't work on desktop Firefox, either.

> Either your browser does not support the Payment Request API, or you do not have a saved payment method. To try out the Payment Request Button live demo, switch to one of the supported browsers below, and make sure you have a saved payment method.

Desktop Firefox doesn’t use the Apple WebKit engine on the backend, so that’s up to the Firefox Desktop team to implement on their own (and tie into the OS native if available, which I suspect depends on you running the latest macOS beta, assuming they’re working on it yet).

EDIT: Which they’re not, per above.

Apple Pay does not work in non-Safari WebKit browsers on macOS as of Ventura beta 4.

Firefox doesn't implement Payment Request, so no Payment Request based payment methods would work.

It's implemented but off by default; there's a `dom.payments.request.enabled` feature flag, but it doesn't make the Stripe demo work.

The API isn't new but being able to use it in 3rd party browsers on iOS is.

Is this intended for actual non-Safari browsers like actual Chrome or Firefox on iOS or just what there is now where Chrome and Firefox on top of the same WebKit engine as Safari?

Everything is still Safari underneath. That’s probably never changing as long as Apple has a say (that new EU law may force it).

But this would mean you could use ApplePay from the current FireFox app.

Letting all browsers with a Safari engine use all the features of Safari-Safari fed be a way to nudge users to keep using Safari browsers instead of other browser engines, when that EU law forces Apple to open up the platform. The other browsers could be forever behind is iOS features. However that's going to make the browser experience closer to native.

I'm glad Apple is opening up features for other browsers to use on iOS, but I don't understand how this nudges users? As soon as it is permitted, Firefox, Chrome, etc will switch from their WebKit based implementations to using their own engines.

I might be wrong but if the upgrade from Chrome-Safari to Chrome-Chrome means that users lose Apple Pay inside the browser, something they just got used to have, maybe they switch to Safari-Safari to keep the feature.

You mean everything is WebKit underneath. Safari and Chrome on iOS are very different browsers.

No, I believe they meant Safari underneath, which is often used as shorthand for the specific rendering engine based on WebKit that powers Safari on iOS and comes with its own quirks. Chrome does not use the same engine on any other platform as it has deviated significantly.

The section on “Apple’s Open Source Claim” in this blog post [1] goes into a lot more detail on the relationship between Safari, WebKit, and the Chrome/Chromium rendering engine.

[1] https://infrequently.org/2021/08/webkit-ios-deep-dive/