But, the advantage of /custom: It uses less personalized results, and it returns exactly 20KiB of data – which is why it still loads so fast.

There was a day when I just wrote a small script to open all sites mentioned in Google’s robots.txt (which did not return 404) in a separate tab. That’s how I found it.

As far as I know, some partners actually still embed /custom (I’ve only seen it at a newspaper a few months ago), so removing it might be problematic.