Support email signup universal link redirect

[percarlsen]

I'm building a flutter app primarily for iOS (for now). The app has email signup, and I want to redirect the user to a certain screen after pressing the link in the confirmation email. To do so, I'm configuring the SITE_URL in supabase to point to the page I want to direct the user to. The issue is that my app uses universal links (as per Apple's recommendation), but the SITE_URL only supports custom schemes, not universal links (documentation).

I've worked around this for now by using custom scheme for this purpose only, but I'd prefer to only use universal link. Would it be possible to support universal links in SITE_URL?

[dshukertjr]

Universal link as in a regular URL for a website, correct? You can certainly add regular URLs for a website into SITE_URL or the Redirect URLs in your Supabase dashboard. Supabase fully supports both custom schemes and universal links.

[percarlsen]

Thanks for answering! As in a regular URL for a website, yes :-) In that case, the documentation (link) might be wrong?

The redirect callback url should have this format [YOUR_SCHEME]://[YOUR_HOSTNAME]. Here, io.supabase.flutterquickstart://login-callback is just an example, you can choose whatever you would like for YOUR_SCHEME and YOUR_HOSTNAME as long as the scheme is unique across the user's device. For this reason, typically a reverse domain of your website is used.

I am using deep link with regular URL for all other purposes in the same app, and it works just fine. E.g. if I press the url https://my-domain.com/foo, the user is directed to the /foo page in the app, indicating that the deep linking is configured properly. However when configuring the redirect with email signup, it doesn't work when I set SITE_URL to that regular URL (I have tried various variations with/without trailing slash, with/without https, http, www etc). The link is just opened in the browser instead of opening the app. If I set SITE_URL to com.my-domain://foo, it works fine - I'd just like to avoid doing this to stay in line with Apple's recommendation.

[dshukertjr]

@percarlsen Hmm, that is weird. If you are taken to the correct link upon clicking the sign-up confirmation link, then everything should be set up properly on the Supabase's end...

[percarlsen]

Something could of course be wrong with the setup on my end, but I don't really know how to further debug this. It does seem a bit unlikely though as I've already confirmed that normal URL deep links works fine in other contexts. I can give it another go later this week, maybe I've missed something.

[Vedsaga]

The same issues, we were dealing few days back, at the end came to know that it's not issue with the Supabase. Instead it is the expected behaviour, this is how it should work.

Case 1 - User click on the link

If user click on the link then OS get notified intent to process the uri on which user clicked. And so now OS look through the registered links ( which apps intended to consume) if any App is found which want to consume link ( based on info.plist config) then app hand over the link to that app. From there we continue processing the link in our app normally.

Case 2 - User manually type/copy-paste link in browser

If user manually type/copy-paste standard link (http or https) in browser, then browser does let the intent reach to the OS. Due that OS never gets chance to hand-over the link to the respective app.

It is well-known issues in Chromium browsers which is marked as Won't Fix, and it seems Firefox also adopted same strategy so far as we tested in our app. Not sure about the Safari or any other browsers. Have below shared the links

Case 3 Link Redirect

As url-config in Supabase if we specify the redirect-link as normal http or https which is classified as app-links in iOS, then as soon Supabase redirect to http or https, browser does not let intent to reach the OS, which is app never opens. As mentioned in the case 2 just above.

However is uri does not contain typical http or https schema, then browser hand-over the URI to OS, which then hand-over the Link to respective app.

Links References

Stackoverflow Feb 11, 2020 -> Deep linking working with adb, not in browser

Chromium Issue May 6, 2015 -> Allow generation of a link to go to fallback URL when typed in and go to market when clicked

Github Sep 5, 2017 -> [Android] Deep Linking not working from Browser

Stackoverflow May 6, 2016 -> Deep linking not working in chrome

Hope this helps...

cc:
@percarlsen

[percarlsen]

Thanks for the detailed description @Vedsaga! I have Brave browser, which uses Chromium, on my test device, so that probably explains why I can't get it to work. But if I understand correctly you suggest that it would work if Safari was the default browser? I'll give that a go.

Update: confirming that redirecting to a regular URL, e.g. https://my-domain.com/foo, works fine when Safari is the default browser on the device.

[Vedsaga]

It seems even in Safari they have some what similar behaviour to Chromium...

How to get a universal link to open the app instead of safari?

cc:
@percarlsen

[percarlsen]

@Vedsaga just updated my message above confirming that I'm able to make it work when safari is the default browser. The SO thread you share is pretty old and might not be relevant anymore.

[Vedsaga]

That's great news, yaa that was 8 year old thread...