Twitter is a publicly-traded company, and as such, its quarterly earnings reports always include data about the platform — including the amount of active users. The company has historically never revealed how many active daily users Twitter has, only the amount of users who log in (at least) once a month. In its Q4 earnings report, Twitter has revealed how many people log into the platform daily, among other information.
According to the report, Twitter has 126 million daily users. The count only includes "monetizable users," or those logging in via the official Twitter website or mobile apps. For comparison, Snapchat has 186 million daily users, while Facebook has 1.52 billion daily users across all its properties (FB, Instagram, FB Messenger, WhatsApp, etc.). The report also says revenue was up 24% year-over-year for Q4 2018, with a GAAP net margin of 28%.
Twitter dropped once again in monthly active users, from 326 million in Q3 to 321 million in Q4. The company says it will not include the monthly count in future reports, saying, "We want to align our external stakeholders around one metric that reflects our goal of delivering value to people on Twitter every day and monetizing that usage."