Snap stock sinks nearly 20% on revenue miss

Snap Inc.’s stock plunged more than 18% in extended trading Thursday after the social-media company reported a decline in revenue as it retools its ad platform.

Revenue dropped 7% to $988.6 million, from $1.06 billion a year ago. Analysts surveyed by FactSet had expected on average a net loss of a penny a share on revenue of $1 billion.

Sales…