Twitter shares finished Friday 20% down at market close after reporting a decline in monthly active users during the second quarter, CNBC reports.

The big picture, from Axios' Dan Primack: The trouble here isn't revenue (it beat estimates) or earnings (it hit its number). Instead, it's about a decline in "monthly active users," a figure that was depressed for reasons like new privacy rules in Europe, a purging of fake/abusive accounts, and not moving to paid SMS carrier relationships.

• Axios' Sara Fischer reported earlier this month that Twitter said "the removed accounts will not impact its monthly active user account."

Go deeper:

• Twitter has been suspending more than 1 million fake accounts per day
• A look at Twitter's supposed conservative "shadow ban"