When IndexNow was first announced by Microsoft Bing in October, it was not yet at a point where the participating search engines we co-sharing URLs - but that is no longer the case. Participating IndexNow search engines, which is still just Microsoft Bing and Yandex, are now co-sharing URLs.
That means when you submit a URL through IndexNow that is submitted through Microsoft Bing, it will be instantly shared with Yandex as well. The same works the other way, submit a URL to Yandex and Microsoft Bing will get it instantly.
Plus, Microsoft said that you no longer have to use https://www.bing.com/IndexNow?url=url-changed&key=your-key or https://yandex.com/indexnow?url=url-changed&key=your-key to submit the URLs, you can use https://api.indexnow.org/indexnow?url=url-changed&key=your-key and the URLs will be shared with Bing and Yandex.
If Google does plan to adopt it, I suspect webmaster/site owner adoption will explode. Right now, Microsoft said 80,000 websites have "started publishing and reaping the benefits of faster submission to indexation" through IndexNow - but in November that number was 60,000 and all through Cloudflare's integration (which we use here by the way). So it seems adoption has been slow?
But Microsoft released a IndexNow WordPress plugin so hopefully that will help a little?
In any event, the key new pieces here are these three points:
(1) IndexNow's protocol is now co-sharing URLs with participating search engines.
(2) api.indexnow.org can now be used to submit URLs to.
(3) IndexNow us now used by 80,0000 websites.
Forum discussion at Twitter.
