To restrict people’s access to some websites and social networks is a way for the Islamic Republic of Iran to control the people, especially its opponents. But the reason why a given website and social network is banned is different.
Some sites, mobile applications, and social media were developed by countries hostile to the Iranian regime. The regime blocks these platforms out of fear of targeted propaganda against the Iranian regime. It also wants to prevent that information is collected from inside Iran. That is why the Viber messenger and the Waze application owned by Israeli companies or some news networks like the BBC are banned in Iran.
Popular social networks with many Iranian subscribers (like YouTube, Facebook, Twitter) are also banned. The Iranian regime uses these platforms to get information about its citizens. But when the administrators of the applications refuse to share users’ information, the Iranian regime responds by denying access to the Iranians.
Any websites with pornographic content are also blocked based on Islamic Sharia law.
The fact that many social media and websites are not accessible in Iran does not mean that the Iranians do not have access to them. You will find many Iranians on WhatsApp, Facebook, etc.
The VPN (Virtual Private Network) enables the Iranians to access anything blocked by the regime. Strangely enough, the officials of the Islamic Republic of Iran also use these websites and networks regardless of the legal restrictions they imposed themselves. Foreign tourists can also easily use VPN to access any of these sites and banned social media.
The main problem for foreign tourists is when the host country restricts access to social networks and sites for users located in Iran. The PayPal software and Tinder dating site or some online stores such as Amazon are blocked through the IP address of Iran. VPN does not help you in this case either.