John Mueller of Google confirmed this morning on Twitter that Google now supports JSON-LD format/schema for breadcrumbs.
Currently, the documentation for breadcrumb schema makes no mention of JSON-LD, but John Mueller said that will change.
In addition, it seems like the Google Structured Data Testing Tool also doesn't recognize JSON-LD breadcrumbs.
But John Mueller said Google does indeed support it.
Here are the set of tweets:
@seerl We support JSON-LD breadcrumbs. The docs should be updated at some point too :)
— John Mueller (@JohnMu) August 12, 2016
Here is a screen shot of the document saying Google doesn't support JSON-LD for breadcrumbs:
Forum discussion at Twitter.