To comply with US sanctions, GitHub is limiting access to the site for users based in Crimea, Iran, and Syria.

The Microsoft-owned platform has banned users in the affected countries from operating private code repositories and accessing paid services, GitHub CEO Nat Friedman said on Saturday.

"We're not doing this because we want to; we're doing it because we have to," Friedman said in a tweet thread, citing US trade control laws. The new restrictions also apply to users based in North Korea and Cuba.

GitHub is a popular platform for programmers across the world to host and promote their coding projects, many of which can be open source. So far, GitHub hasn't said how many users and companies might be affected. But last week a Crimea-based developer said the site had restricted access to his private code repository, forcing his gaming-related app to temporarily shut down.

However, GitHub doesn't plan on cutting off all access to the site. Affected users will still be able to host coding projects on the platform as long as they remain public and available to all. Users will also be able to communicate to others on the platform, but only for personal purposes, not for commercial reasons.

"We believe that offering those free services supports US foreign policy of encouraging the free flow of information and free speech in those markets," GitHub says in support document explaining the policy.

The platform is blocking users based on their apparent location, which is determined by factors such as IP address and payment history. So affected users could use VPN services to get around the ban. Users wrongly flagged by the new restrictions can file an appeal.