Google Subpoenaed for Details on Its Ad Business

WASHINGTON—The probe into Alphabet Inc. GOOG 1.15% ’s Google unit by a coalition of state attorneys general is zeroing in on the search company’s dominant presence in the digital advertising market, according to a civil subpoena.

The subpoena, sent by Texas Attorney General Ken Paxton, includes more than 200 questions and demands for records. Many of the questions appear designed to solicit evidence that Google engaged in anticompetitive conduct in building up its powerful position.

For instance, the subpoena asks for information about Google’s “business rationale” for acquiring several of...