Internet censorship explained: What it is and how it works

Censorship is no longer limited to history books or a few countries—it increasingly affects users around the world, including in democratic nations.

Some restrictions are obvious—entire websites banned, social media shut down, independent news silenced. Others are subtle. Algorithms hide certain topics, internet service providers (ISPs) slow down specific websites, and search engines manipulate search results to omit certain websites.

Governments may block content to manage information flow or limit political dissent, while companies can limit access to follow laws, protect their interests, or avoid backlash. Even schools restrict websites they consider distracting or inappropriate.

This guide breaks down how censorship works, whom it affects, and the reasons organizations and governments censor the internet.

What is internet censorship?

Internet censorship is the practice of restricting access to online content. It can be done in many ways:

• Blocking: ISPs prevent access to certain websites by blacklisting their IP addresses or by preventing their domain names from resolving to an IP address.
• Filtering: Governments and platforms restrict specific words, topics, or categories.
• Throttling: ISPs intentionally slow down certain websites, making them difficult to use.
• Geoblocking: Content is limited by location, like streaming services with country-specific libraries.
• Deep packet inspection (DPI): Authorities scan and block restricted online activities, such as VPN use.

No matter the method, censorship affects what people can learn, share, and discuss online.

What content is commonly blocked?

Censorship isn’t random. The same types of content tend to be restricted across various countries and platforms.

1. News and political websites

Authoritarian governments often block independent news sources that criticize their policies. Even in countries with democratically elected governments, certain websites may be demoted in search rankings to limit their reach.

2. Social media platforms

Platforms like Twitter, Facebook, and TikTok are common targets. Governments restrict them to control public discourse, while companies owning these platforms moderate content to comply with local laws and protect their business interests.

3. Encrypted communication tools

Apps like Signal and WhatsApp, which employ end-to-end encryption, are restricted in some regions to limit unmonitored communication. These apps make surveillance difficult, which is why they’re often targeted.

4. Human rights and activist websites

Websites that report on government misconduct or advocate for freedom of expression are often censored in countries with strict control over information.

5. Adult content

Pornography and other explicit content are banned in many countries, either for religious, cultural, or moral reasons. However, these restrictions often go beyond adult content, affecting discussions on reproductive health, sex education, and LGBTQ+ rights.

6. Pirated content

Pirated content is often blocked because it violates copyright laws. Governments, ISPs, and platforms take action to prevent illegal distribution of movies, music, software, and books to protect the rights of creators and businesses.

7. Streaming, entertainment, and gambling

Geoblocking limits access to content based on location—like how popular streaming platforms have different libraries depending on the country or how online casinos only allow players from specific countries to access their websites to comply with local laws.

8. Search engine results

Search engines can manipulate results to hide certain topics, like ongoing protests or even historical events, ensuring that users only see information that aligns with certain interests.

9. Privacy tools

Since they can be used to access restricted content, privacy tools like VPNs are often its targets. Most countries don’t ban VPN use in general, but some may only allow state-approved ones, restricting access to independent VPN services.

Where does online censorship happen?

Internet censorship happens everywhere. Governments, workplaces, schools, and social media platforms all place restrictions.

In entire countries: Government censorship

Governments are some of the biggest forces behind internet censorship. There are several ways governments can censor the internet:

• ISP-level restrictions: ISPs may be required to block websites or slow down traffic to make access more difficult. (It’s also worth noting that ISPs can block or slow down websites on their own to promote their business interests in countries that don’t have net neutrality.)
• National firewalls: Some governments use sophisticated filters that monitor and block traffic in real-time, cutting off access to restricted content.
• Surveillance laws: Some governments don’t block websites directly but monitor users, creating fear around accessing certain content or speaking openly.
• Temporary blackouts: In times of political unrest, some regimes cut off internet access entirely to stop protests from organizing.

Why do governments and organizations censor the internet? There are many different reasons, some of which regular internet users may agree with and approve of, while some they may find wrongful, oppressive, or paternalistic. Common reasons include:

• Political control: Silencing critics, restricting opposition, and stopping protests.
• National security: Blocking terrorist content, cyber threats, or foreign propaganda.
• Moral, religious, and cultural reasons: Blocking harmful content such as child exploitation, hate speech, blasphemy, heresy, or religious extremism.

In the workplace: Corporate censorship

Companies also censor content, though for different reasons, all of which come down to protecting their business interests. Common restrictions include:

• Blocking social media and restricting streaming services: Platforms like Facebook, Instagram, and Twitter are often off-limits to prevent distractions. Sites like Netflix and YouTube may be blocked, too, to save bandwidth and keep employees focused.
• Banning messaging apps: Employers may prevent access to WhatsApp, Discord, Telegram, or similar apps to keep work communication on approved platforms for security reasons and to monitor employee communications.

On social media platforms: Content moderation as a form of censorship

Social media has enabled many voices to be heard, but that doesn’t mean everything gets through. Sometimes, governments push for censorship. Other times, it’s the platforms themselves—guided by advertisers, policies, and algorithms that may limit certain content.

Censorship on social media takes several forms:

• Algorithmic censorship: Platforms use algorithms to decide what posts get seen. If a topic is controversial, the algorithm might limit its reach, even if it isn’t officially banned. It’s worth noting that this form of censorship is not always intentional—it can simply be a “side effect” of how an algorithm works.
• Content takedowns: Posts that violate platform rules—which may vary in clarity or consistency—can be removed.
• Shadow banning: A user’s posts might still exist but become nearly invisible, reducing engagement without them even knowing. Most social media platforms deny shadow banning or avoid using the term, but some have admitted to limiting content visibility under certain conditions, calling the practice “visibility filtering,” “demotion,” or “deprioritization” rather than outright banning.

In the classroom: School and university network restrictions

Schools and universities also limit internet access, mainly to keep students focused and ensure a safe learning environment, which is a cause most people approve of. However, their restrictions can sometimes feel excessive.

What schools typically block:

• Social media and gaming sites: To prevent distractions during class and keep students from playing during lessons.
• Mature or restricted content: Schools filter out adult content, violence, and other topics they deem inappropriate.

At home: Parental controls

Parents or guardians may install parental control software on kids’ devices to censor content generally considered harmful for children (adult content or violence, for example), filter their messaging apps to protect them from hate speech and predators, or simply to prevent excessive use of the internet.

While generally not disapproved of, this form of censorship can have negative effects, especially if parents are not transparent with their children about their use of parental controls (for example, parents of teenagers secretly reading their private chats).

How does internet censorship work?

Time to dive into the technical side of internet censorship, exploring the exact methods used to control access to online information.

Manipulating DNS to restrict access

DNS (domain name system) is like the internet’s phone book. It translates website names (like expressvpn.com) into numerical IP addresses that computers understand (more about them in the next section). When you type a web address, your ISP’s DNS server looks up the correct IP and connects you.Censors can manipulate this process to block websites at the DNS level by:

• DNS filtering: ISPs block certain websites by modifying their DNS servers. If an internet user tries to visit a banned site, they’ll get an error message.
• DNS hijacking: Instead of showing an error, users are redirected to a different page—sometimes a government warning or a fake version of the real site.
• Blocking third-party DNS services: Since some internet users try to go around DNS blocks by switching to public DNS servers like Google or Cloudflare, some ISPs block these to maintain censorship.

Blocking IP addresses to prevent website access

Every website has an IP address—a string of numbers that acts like an online home address—usually shared with all the websites hosted on the same server. Any device you have connected to the internet also has an IP address you can check here if you’re curious. The public IP address is usually shared by all devices on the same network.

Instead of targeting website names, authorities or ISPs can block the IP itself, making the entire server unreachable. They create lists of “banned” IPs and prevent users from connecting to them. Now, because websites often share IP addresses (to continue our home address analogy, they happen to “live in the same house”—the same web server), blocking one site can unintentionally take down many others.

Websites themselves can block access to certain IP addresses as well. However, their reasons usually differ from those of ISPs—they usually block users who violate platform rules (such as spammers), hackers, or users from certain locations (for example, a UK gambling website may block access to non-UK visitors to conform with local regulations).

Filtering URLs and keywords to control content

Censorship doesn’t just block websites—it can also target words and topics.

• Search engine filtering: Governments can force search engines to remove results for banned topics, like protests or human rights.
• ISP-level keyword blocking (HTTP only): If a webpage contains restricted words, the connection might be blocked automatically.
• Social media restrictions: Platforms may reduce the reach of posts with “sensitive” words without directly banning them.

Filtering internet traffic at the packet level

Packet filtering is a technique that blocks access to specific IP addresses, ports, or protocols associated with restricted websites or services. Here’s how it works.

Each packet contains a header and payload. The header includes IP addresses (source/destination), port numbers, and protocol (TCP, UDP, etc.). The payload is the actual data being sent (like part of a web page, a file, or a search query)

Packet filters analyze the header. If a packet is headed to a known banned server, it gets dropped. Another method is port blocking. Certain services use specific ports (e.g., 443 for HTTPS); blocking these ports can prevent access.

While packet filtering is generally effective, users have multiple ways to bypass restrictions. That’s why, to enforce stricter censorship, packet filtering is often combined with Deep Packet Inspection (DPI).

Inspecting internet traffic to enforce censorship

Some governments use DPI, allowing ISPs to analyze internet traffic in real time. Instead of just blocking sites or keywords, DPI scans data for restricted activity.

• Blocking VPNs and Tor: DPI detects encrypted VPN traffic (although it can’t break this encryption) and blocks connections.
• Filtering sensitive content: DPI allows censors to scan messages, images, and even voice calls for banned topics.
• Prioritizing or throttling traffic: Some governments slow down or disrupt traffic to certain websites that they don’t want people visiting (like international news sites), while other, “non-problematic” services get normal speeds.

Interfering with encryption

In extreme cases, authorities weaken encryption or push users onto slower, less secure connections that can be monitored more easily.

Governments or ISPs may pressurize companies to deliberately introduce vulnerabilities in encryption protocols (backdoors).

Another tactic involves SSL/TLS stripping. Normally, when you connect to a website, your connection to it is encrypted by HTTPS (HyperText Transfer Protocol Secure), preventing others from intercepting sensitive data like passwords or credit card details. However, in SSL/TLS stripping, encrypted HTTPS connections are downgraded to unencrypted HTTP ones, allowing for surveillance and data interception.

Conclusion: Internet censorship today

Today, the internet is more censored than ever. According to the “Freedom on the Net” 2024 report by the Washington-based nonprofit Freedom House, global internet freedom has declined for the 14th consecutive year, as an increasing number of governments turn to censorship and surveillance to shape public discourse.

From widespread content filtering to internet shutdowns during elections—and a range of tactics we describe above in between—censorship has shifted from isolated incidents to systematic strategies. This global trend signals a troubling move toward tighter information control, where access to a free and open internet is no longer the norm but a privilege increasingly shaped by geographic, political, and regulatory factors.