At Google IO 2019, it was announced that the Structured Data Testing Tool would be replaced by the Rich Results Testing Tool.
Googlebot now indexes web pages using the latest Chromium instead of the old Chrome 42, which means you can also alleviate SEO issues you may have encountered in the past with structured data support.
Jason Barnard gave an interesting talk at SMX London 2019 on how Google search ranking works , and according to his theory, there are seven ranking factors we can rely on; structured data is definitely one of them.
Builtvisible ’s guide to Microdata, JSON-LD, and Schema.org contains everything you need to know about using structured data on your website.
Here's a beginner 's guide to JSON -LD by Alexis Sanders .
Last but not least, there are a lot of articles, presentations and posts that go into more depth on the official JSON for Linking Data website.
Advanced Web Ranking’s HTML research relies solely on analyzing indexed pages. Interestingly, although not stated in the guidelines, Google does not seem to care about structured data on indexed pages, as Gary Illies explained in a Stack Overflow post a few years ago . We found a total of 2,727,045 features in the JSON-LD structured data type that Google understands :
json-ld-chart.png
The pie chart shows the type of structured data that Google understands, with the Sitelinks search box coming in at 49.7% – the highest value.
Article 35,961
Breadcrumb 30,306
Book 143
Carousel 13,884
Corporate contact 41,588
Course 676
Critic review 2,740
Dataset 28
Employer aggregate rating 7
Event 18,385
Fact check 7
FAQ page 16
How-to 8
Job netherlands mobile database posting 355
Livestream 232
Local business 200,974
Logo 442,324
Media 1,274
Occupation 0
Product 16,090
Q&A page 20
Recipe 434
Review snippet 72,732
Sitelinks searchbox 1,354,754
Social profile 478,099
Software app 780
Speakable 516
Subscription and paywalled content 363
Video 14,349
rel=canonical
The rel=canonical element, often referred to as a "canonical link," is an HTML element that helps webmasters prevent duplicate content problems. It does this by specifying a "canonical URL," the "preferred" version of a web page.