In October 2017 Twitter announced an Advertising Transparency Center saying “that it will offer everyone visibility into who is advertising on Twitter, details behind those ads, and tools to share your feedback.” As of this date, there has been no Ad Transparency Center nor any updates on its progress.

Twitter previously said the Transparency Center will show:

• All ads that are currently running on Twitter, including Promoted-Only ads
• How long ads have been running
• Ad creative associated with those campaigns
• Ads targeted to you, as well as personalized information on which ads you are eligible to receive based on targeting

Is Twitter going to launch the Transparency Center or has it changed its mind? (Buzzfeed News)