Google Photos // Google’s OAuth URI validation rules

Details
Today you might have seen emails from Google telling you details about your Google App which handles your Google Photos credentials. 
 
Those mails might look like that: 
 

[Action Advised] Inactive registered OAuth URIs for your project(s) will be removed from Google Developer Console by July 12, 2021, for non-compliance with URI validation rules

Hello Google Developer,

We are writing to let you know that you have inactive OAuth redirect URIs and JavaScript origins in your Google Cloud project that are not in compliance with Google’s OAuth URI validation rules.

  • On July 12, 2021, we will remove all inactive URIs that are invalid.
  • On September 13, 2021, we will remove all URIs that are not in compliance with redirect URIs and Javascript origins rules (including formerly inactive URIs trying to become active).

What do I need to do to be compliant?

  • If these inactive OAuth redirect URIs and JavaScript origins are no longer needed, you can remove them from your Google Cloud project. If they remain inactive, they will be automatically deleted after July 12, 2021.
  • If your app still needs to use these URIs, please update your app and OAuth configuration from the Google Developer Console to use redirect URIs or JavaScript origins that are compliant with the OAuth URI validation rules by September 13, 2021.

The following Google Cloud project(s), which has/have registered OAuth redirect URIs and JavaScript origins without usage for over 90 days, and which will be removed by July 12, 2021:

  • Project ID: eg-demo3
    • Client: 1234567890-xxxxxxxxxxxxxxxxxxxxxxxxxxxxx.apps.googleusercontent.com
      • URI: http://eg.io

If you have any questions or concerns regarding these changes, please review the documentation provided above in this email.

Sincerely,

The Google Developer Team

Or like this

[Action Required] Update or remove non-compliant registered OAuth URIs for your project(s) by September 13, 2021

Hello Google Developer,

We are writing to let you know that you have active OAuth redirect URIs and JavaScript origins in your Google Cloud project that are not in compliance with Google’s OAuth URI validation rules. All noncompliant active URIs will be removed, along with their origins, by September 13, 2021.

What do I need to do to be compliant?

Please update your app and OAuth configuration in the Google Developer Console to use redirect URIs or JavaScript origins that are compliant with the OAuth URI validation rules by September 13, 2021.

The following Google Cloud project(s), which has/have registered URIs and origins that are out of compliance, and which will be removed if you do not update your OAuth flow to use compliant redirect URIs and Javascript origins by September 13, 2021:

  • Project ID: event-gallery-for-svenbluegede
    • Client: 1234567890-xxxxxxxxxxxxxxxxxxxxxxxxxxxx.apps.googleusercontent.com
      • URI: http://eg.test

If you have any questions or concerns regarding these changes, please review the documentation provided above in this email.

Sincerely,

The Google Developer Team

 
First, don't worry! But you might need to do something. 
The Google Photos of Event Gallery uses the Google Login dialog to collect the necessary credentials to access your images. When the Google login dialog opened and collected the necessary data, it needs a URL to return to. Also, the dialog will only open properly if it was called from the correct URL. Those URLs are the OAuth redirect URIs and JavaScript origins. They need to fulfill a couple of criteria now: 
 
  • use HTTPS
  • use public top-level domains
  • use those domains from time to time, so Google will not think they are outdated.
  • you can find the complete rules here: https://developers.google.com/identity/protocols/oauth2/web-server#uri-validation
 
What happens if you do nothing? Nothing. The credentials, you stored in your system stay valid. Your website will continue delivering image from Google Photos. Only in case you need to renew your credentials, you have to fix the OAuth redirect URIs and JavaScript origins
 

How to fix this

 
Log in to your Google developer console and change the configuration of your OAuth credentials (see screenshot). 4 and 5 mark invalid URLs which need to be removed or adjusted. That's already it.