The EU on Friday used new regulatory powers to query Meta about ad-free subscriptions to Facebook and Instagram as well as claims some voices are suppressed online in a phenomenon known as "shadow banning".
The European Commission made a request for information under the mammoth content law known as the Digital Services Act (DSA), which came into force last August for online giants like Meta.
The EU's executive arm has launched a wave of probes under the DSA to quiz platforms on how they are addressing concerns from consumer protection to children's activity online.
The latest request is a first step in a possible compliance procedure, but does not itself suggest there have been breaches of the law or a move towards punishment.
The commission's list of questions is long.
It wants more information about Meta's offer from November for Facebook and Instagram users in Europe to pay monthly subscriptions to use the platforms without adverts and without their data being tracked for targeted advertising.
Privacy and consumer rights campaigners have slammed the subscriptions, and filed separate formal complaints with data protection authorities.
Now the commission wants Meta to give "additional information on the measures it has taken to comply with its obligations concerning Facebook and Instagram's advertising practices, recommender systems and risk assessments" related to subscriptions.
Recommender algorithms are used by platforms to push more personalised content. Under the DSA, platforms must mitigate risks arising from such systems as well as offer users a non-personalised feed that does not rely on "profiling".
Brussels also demanded Meta "provide information related to the practice of so-called shadow banning and the launch of Threads", a spin-off of the Instagram photo app.
Individuals, including politicians, and groups claim that some media platforms practice shadow banning -- actively limiting the reach of certain viewpoints, including conservative opinions.
The platforms have firmly denied such claims.
Since the outbreak of war in Gaza in October, there have been accusations against platforms, including Facebook and Instagram, of censoring pro-Palestinian voices in particular.
Meta must respond to the EU's questions by March 22.
The commission is also seeking "additional information" on issues including terrorist content, risk management related to elections, and the protection of minors, after previous requests made since October 2023.
It added Meta had until March 15 to respond on these issues.
Meta did not respond immediately to AFP's request for comment.