Twitter is blocking people from viewing tweets and profiles on its website unless they are signed in to the social media site.

When an unregistered user tries to view a tweet, the site prompts them to log in or sign up for a Twitter account. As of Friday, users could still see tweets that appeared in Google searches or were embedded in other sites.

Twitter has long relied on the accessibility of its tweets around the web to drive interest in the site — for instance, through users sending tweets to friends or contacts who don’t have accounts. The company, which hasn’t publicly announced a change in policy, didn’t immediately respond to a request for comment.

Owner Elon Musk has made a string of product changes since he took over the San Francisco-based company last year. In March, Twitter began charging for access to its application programming interface, or API. Twitter’s API was used by popular third-party apps like the now-defunct Tweetbot and Twitterific, in addition to academic researchers. Now Twitter is charging customers $42,000 per month to access just 1% of tweets.

In April, Musk temporarily disabled likes, replies and retweets if a tweet had a link to Substack, the newsletter platform. After complaints, Musk then reversed that change.