Search engines normally discover changes by crawling a site again, which can take time. IndexNow reverses that: when you publish or change a page, your site sends a simple notification, which the IndexNow site describes as “a simple ping”, so participating engines know to look.
IndexNow.org lists support from Microsoft Bing, Naver, Seznam.cz, Yandex and Yep. Its documentation for search engines says participants agree to share the URLs they receive with the other participating engines, so one notification can reach several of them.
Why it matters for AI visibility: answers that search the web while answering can only find what a search index already holds. If you launch a product page or correct an old price, getting the new version indexed sooner gives searching answers a chance to read it sooner. IndexNow doesn’t decide whether a page is shown or cited; it only speeds up discovery.
Some website platforms and plugins can send these notifications automatically, and Bing Webmaster Tools covers IndexNow too. Read Bing Webmaster Tools and IndexNow.