How do you measure success when experimenting with new content formats?

Depends where do you place the content. But in most cases I focus on Google Analytics and the organic visitors, that come through that content. i do not focus on views or likes so much.

Success in experimenting with new content formats can be measured by tracking engagement (likes, shares, comments), reach (how many people saw it), feedback (how people respond), and whether it meets your goals (e.g., brand awareness, conversions).