In 2015 Google said they would deprecate the AJAX crawling schema and then in 2017, two years later, Google did do that. A year after that, Google said they stopped crawling #! for the most part. But today, in 2020, Google said technically they still do #1 crawling.

John Mueller of Google said on Twitter “for the moment, we would still support it,” it being #1 crawling. “But since we’ve flagged it as deprecated so long ago, I wouldn’t assume that it’ll stick around forever,” he added. Yea, do not go building new sites on this framework:

Here are those tweets:

Then Google went on about why is it not documented that Google technically still crawls these?

Just an interesting tidbit I thought some of you might appreciate. I do not recommend you build sites that depend on that old AJAX crawling schema. I honestly thought by now it would not be supported at all.

Forum discussion at Twitter.

Update in 2021: I am not sure when unofficial support was removed, but it may have been?