How to disable Google One Tap sign-up prompts?

In your Adblocker, block all content from smartlock.google.com. That will be the end of these popups.

This popup is provided by a Google service website owners can select to integrate on their websites.

This has worked for me.

Add this line to your AdBlock Chrome extension under custom options:

accounts.google.com/gsi/*

I started seeing pop-ups consistent with the appearance of the Google One-tap sign-in, but they extend beyond the browser window.

Learn about third-party sign-in

Third-party sign-in is a type of federated sign-in that allows you to log in with an identity service, instead of creating unique login credentials for each individual website you visit. If you allow third-party sign-in prompts, then as you browse the web, you may receive dialogs that ask if you want to sign in with an identity service.

You can sign into websites with Chrome through an identity service of your choice. An identity service stores and manages your sign-in information and identity across the web per your permission.

Attempts to follow the myriad suggestions online to disable this in your Google account settings did nothing. But I finally found a Chrome setting for Third-party sign-in:

chrome://settings/content/federatedIdentityApi

Third-party sign-in

Lets you sign in to websites using the account you have with an identity service

Default behavior — Sites automatically follow this setting when you visit them

• Sites can show sign-in prompts from identity services
• Block sign-in prompts from identity services

Selecting "Block sign-in prompts from identity services" here seems to suppress the new version of this pop-up.

Install the uBlock Origin Firefox extension, then:

1. Click the extension icon on the address bar,
2. Click the gears icon (near the bottom),
3. Click "My Filters" tab,
4. Paste into the box, on a new line: accounts.google.com/gsi/*,
5. Click "✔ Apply Changes".

Daniel's answer works on medium.com^* (and probably others) but not in pinterest. That site keeps nagging you on every visit, and uses pop-up elements containing multiple 'random' ID strings (so you can't just filter on these). The substring to filter on for blocking the popup with AdBlock Plus seems to be:

&origin=https%3A%2F%2Fnl.pinterest.com

^{* Note that medium.com prompts you only once anyway; your (non-)response is kept in a cookie.}

uBlock Origin and other options won't work in Safari. Create a file ending with .css extension. Add the following:

/* prevent google one tap login window */
iframe[src^="https://accounts.google.com/gsi/iframe/"] {
  display: none !important;
}

Save the file; then point to it in the Safari -> Settings -> Advanced page's Style sheet: dropdown.

You can get more or less specific with the src value, if desired, but the above should work everywhere.

Edit: The above works on macOS without adding any extensions. To disable this prompt in Safari on iOS, use the free Userscripts app/extension with the my gist on Github for a file that works. (You can skip step 5 and navigate to this gist in step 6 of that post.)

The settings page now tells you that it needs to be adjusted in your browser, for desktop use:

That leads eventually to a help article with these steps:

1. On your computer, open Chrome.
2. At the top right, click More Organize and then Settings.
3. On the left, click Privacy and security and then Site settings.
4. Under “Content,” click Additional content settings and then Third-party sign-in.
5. Select the setting you like:
   1. Sites can show sign-in prompts from identity services
   2. Block sign-in prompts from identity services

This is a website doing. Not sure why in these days any webmaster might be enticed to foster more Google privacy incursions but here we are.

1. Install uBlock Origin extention
2. Right click the popup
3. Add it to the block list.

Understand One Tap User Experience

connected apps page. The opted-out sessions aren't shown in One Tap. If all Google sessions are opted out, One Tap won't display.

They also detail the specifics of when you will see the next One-Tap pop-up after closing one on the same website:

Exponential Cool Down

If a user closes One Tap by tapping the "X" button in the header, for a time period, One Tap won't display for the same website and in the same browser.

The following exponential time periods are used for cool down.

Consecutive Closing Times	One Tap will be disabled
1	2 hours
2	1 day
3	1 week
4+	4 weeks

The cool down status will be reset after a successful One Tap sign-in.