When Google first said that it was going to deprecate the Structured Data testing tool back in July, folks weren’t thrilled with the idea, so rather than just get rid of it, the company decided that they would move it to schema.org instead.
According to Google, the Structured Data Testing Tool will be migrated to a new domain serving the schema.org community as late as April 2021.
Google said:
“To better support open standards and development experience, we’re refocusing the Structured Data Testing Tool and migrating it to a new domain serving the schema.org community by April 2021. The main purpose of the tool will be to check syntax and compliance of markup with schema.org standards.”