Guide to UK ISP blocking and web filters

Author: Matt Powell

Last updated: 26 March 2024

For several years now, many of the UK's broadband service providers (ISPs) have been filtering and blocking websites. They limit access to content that’s deemed sexually explicit, violent, or dangerous.

Since 2013, all new customers to the four biggest ISPs (Sky Broadband, BT, Virgin Media and TalkTalk), along with many of the smaller providers, were automatically opted-in to web filtering. In 2014, this was extended to all existing subscribers. If you haven't previously chosen to opt out of the filtering, it's likely your connection will be affected.

But what are these filters, what sites do they block, and how can you control them?

What is ISP content filtering?

The web filters introduced by ISPs use network-level filtering of broadband connections to block access to adult and illegal content. The filters can automatically block pages by IP addresses or by examining keywords. ISPs use blacklists to block specific sites as well.

Because this blocking is occurring at the network level, it doesn’t rely on software or hardware in your home and is applied to the entire connection, so filtering works on any connected device.

The advantage for parents is that they don’t need to worry about configuring settings on every bit of hardware that has a web browser. Whether your kids are using a smartphone, tablet, games console or computer, the filtering can prevent them from accessing unsuitable sites.

What sites are blocked by web filters?

Typically, the filters will block sites relating to the following topics:

• Drugs
• Alcohol
• Tobacco
• Pornography and nudity
• Terrorism
• Suicide and self-harm
• Hate speech
• Violence and gore
• Gambling
• Social networking
• File sharing
• Anonymising services
• Dating
• Hacking
• Bullying
• Malware distribution and phishing

Each ISP has its own way of categorising and filtering content. You can find a detailed breakdown of internet censorship for the four biggest ISPs on the Wikipedia page for web blocking.

Broadband providers also block child abuse material and piracy. The Internet Watch Foundation (IWF) monitors child abuse online and maintains a block list. File-sharing sites such as The Pirate Bay are blocked by court orders, along with proxy services designed to bypass the filters. Unlike other categories, these sites cannot be accessed by opting out of the filter.

How do I check if my ISP is blocking a website?

The Open Rights Group maintains the Blocked.org.uk web tool, which can be used to check if internet service providers filter a site. It can also be used to report incorrectly blocked sites that have been reported.

Web filter controversies

The use of web filters in the UK has been controversial. There's no independent oversight of the ban lists, and nothing preventing the government from extending the filter beyond its original mission. People worry that they could, for example, use the filters to clamp down on political dissent. And while the filters can be disabled right now, there’s no rule that says this capability can't be withdrawn in the future.

Another issue is overblocking, which is when there’s an unintentional restriction of legitimate content.

The categories are broad, and perfectly innocent sites can get caught in the net. This can easily affect gaming and dating services. But it’s especially problematic for sites dealing with issues such as eating disorders, mental health, medical advice and domestic violence. As a result, vulnerable people could find it harder to access help and guidance online.

If you choose to enable your ISP web filter, it’s important to consider the impact on your family. Take the time to examine the options and, when possible, you can configure the filters to block unsuitable content without being overly strict. Even then, the filters are far from perfect, so you may have to frequently log in to the filter controls and manually block or unblock sites.

How to control your ISP web filters

The web filters operate on an 'opt-out' basis, which means they’re automatically enabled for broadband subscribers until disabled. So if you’d rather not use them at all, you can simply log in to your customer account controls and cancel all filtering.

As well as a straightforward on/off switch, internet providers offer a variety of options to customise the filters. This allows finer control over the settings to prevent overzealous blocking while protecting your family from unsuitable sites.

The settings vary with each ISP, but most offer some or all of the following options:

Timer

Enable blocking only at specific times, which is helpful if you want to disable the filter for the grown-ups in the house when the kids aren’t using the internet. Some ISPs have a 'watershed' setting for either disabling the filter or switching to adult-only filters at certain times.

Homework mode

A homework mode implements stricter rules to prevent kids from wasting time on social networking or games when they should be studying.

Category controls

All web filters allow you to choose the level of filtering. With some providers, you’re presented with a list of categories that can be enabled/disabled individually, while others offer pre-configured age rating groups or filter levels.

Blocking and safe-listing

If there’s a site that’s fallen outside the filter, or you wish to exclude a specific site from filtering, you can manually specify a URL to allow or disallow it.

How Do ISPs Block Certain Websites?

For ISP blocking to be practical, it has to be able to block websites on all systems. Although this might sound like they’re using a firewall, that’s only one way that providers can block websites. They also use IP blocking, DNS filtering, and deep packet inspection.

IP block and DNS filtering work in a very similar way. Rather than blocking specific keywords, they can block the IP address that you’re trying to connect to or a domain name. When it comes to blocking specific websites, like sites for piracy, this can be pretty practical for them. It can also be easier to override.

The other most commonly used method is deep packet inspection. This is a little more complicated, but it essentially means that the blocking software will look deeper at the websites and what’s on there than would normally be done. This means that your internet provider can block certain words or file types that they think could be considered dangerous for users.

How to adjust your ISP's content filtering

Each ISP has its own name for the filter, and the choice of settings varies, too. Here's a brief guide to the web filters for some of the most popular ISPs. If yours isn’t listed, check the online help pages or contact support for more information.

At this time, not all ISPs offer filtering. While the government pressures providers to implement this system, it is not a legal requirement and many smaller companies have yet to comply.

• How to adjust BT's content filtering: BT Parental Controls

  1. Login to My BT and navigate to the Parental Controls panel.
  2. Choose a pre-set filter levels from Light, Moderate and Strict, or customise the blocked categories. This includes a timer, homework settings and black/whitelisting.
  3. Save your chosen settings.
  4. If a website you later need is blocked, anyone with access to the account details can override the filter for an hour or permanently whitelist the site.

      

• How to control Sky Broadband web filtering: Sky Broadband Shield

  • Visit https://www.sky.com/myaccount/bb-and-talk/broadband-shield and login with your Sky ID account.
  • Choose between the PG, 13 and 18 filters or you can disable the shield. If there are no kids at home, always choose '18' as it’ll only block malware and phishing sites.
  • If there are kids in the house, you can turn on the watershed setting. With this, your settings will switch to '18' automatically after a certain time. You're free to tweak these timers.

• TalkTalk HomeSafe

  • Login to your TalkTalk account page.
  • Click into the KidSafe filter and choose from the nine categories of sites you can filter including topics like gambling.
  • If you want to be able to block your kids from browsing social media and games at certain times, there’s also a homework setting you can put into place.
  • You can also blacklist and whitelist particular websites.
  • If you have an eero Wi-Fi router (see 'TalkTalk router round-up), you'll have to use eero Secure and set up your web filtering settings in the eero app instead.

• Virgin Media Web Safe

  • Log in to your My Virgin Media account.
  • Click on My Apps then Web Safe.
  • If you want to protect children, then click on the Child Safe filter. You’ll be able to block groups of sites by category, configure blocking for specific websites and set a timer for the filter.
  • Virus Safe, on the other hand, is designed to protect against malicious sites. This can provide a useful extra layer of security, but it is still important to have anti-virus software.
    
    For more help, visit www.virginmedia.com/help/broadband/web-safe.

What’s a VPN? Can it work around ISP blocking?

There are times when a website or a service is blocked, and your internet provider doesn’t offer you a way around it. It could be because you’re trying to access something in a different country, or just because your filter is blocking the site, even if you can’t figure out the reason why that particular site is off-limits. That’s when a Virtual Private Network or VPN comes in handy.

A VPN is a tool you can use to make your network more secure. It hides your IP address underneath the one they provide instead. That means that sites that are blocked due to your location or internet provider can now be viewed.

Does incognito mode affect filtering?

You might be wondering if you can use incognito or private browsing mode to view these websites instead, but that won’t work. In incognito mode, your IP address is still visible. The only way it’s considered incognito is that any cookies collected on websites aren’t saved.

That means if you log into something on an incognito tab, you won’t remain logged in if you click out. But this isn’t actually hidden from your provider.

Your ISP can still see what you’ve been looking at, and they can still block websites, too.

Web filtering on mobile broadband and mobile phones

It’s not just fixed-line home broadband that uses website filtering. Mobile networks also censor content online. In fact, mobile networks were way ahead of the game and began web blocking in 2004, following Ofcom’s publication of the UK code of practice for the self-regulation of new forms of content on mobiles.

The mobile networks don’t use the same blocks as home providers. Mobile operators use guidelines developed by the BBFC which classifies sites on a similar basis to an 18-rated film – filtering out sexually explicit, gory, violent, and drug-related content.

However, overblocking is reported to be a significant issue on mobile devices, with many innocent sites falling foul of the filter. What makes this worse is the lack of customisation on some mobile filters. Mobile internet blocks don’t always offer the same level of control as home broadband and may be either on or off, with no way to customise the filters.

Disabling blocking can be more involved, too. To cancel the filter, you'll need to verify your age, which involves either going into a high street store with your ID or providing credit card details specifically on a mobile app or over the phone.

More information about controlling the filters can be found on these network support pages:

EE: content lock and Orange Safeguard

O2: age-restricted content and age verification

Three: accessing adult content on your phone

Vodafone: age restriction support

Expert Summary

With an internet connection, you can access information on just about any topic. But what you might not know is that our online activities are monitored. This doesn’t mean that ISPs are looking at your browsing activity every day, but certain websites are blocked by filters.

Online filters can actually be pretty practical. Using the filtering software offered by your providers, you can protect your children. You can block certain types of sites at specific times, so you can make sure that your kids are only doing what they’re supposed to be. If you want more information on this, you can check our guide on parental controls.

However, sometimes these filters make viewing certain websites difficult and at times like this, it’s worth trying out a VPN. By using a VPN, you can bypass the filters for a short time, and hide your IP address to make sure that your internet is secure. If you’re going to be browsing the internet in public, we highly recommend using a VPN to protect yourself.

Further reading and resources

NSPCC online safety guides

CEOP Safety Centre (assistance with online child abuse and safety)

Internet Watch Foundation (anonymously report illegal sites)

Childline cyberbullying advice