URL Blocking: Good Practice

The IWF and its Members promote policies and practices in order to adhere to the principles of self regulation and transparency. Blocking access to child sexual abuse content by our Members is carried out on a voluntary basis and is a short-term disruption tactic which works alongside the removal of content at source whilst police investigators collect the evidence they require to investigate offenders or identify and rescue the victims from sexual abuse.

Whilst the IWF facilitates this blocking initiative through the provision of a URL list and does not stipulate which blocking method is used, we do provide good practice guidance regarding the way in which blocking is conducted. These recommendations are designed to maintain the principle of transparency and minimise over-blocking and latency issues:

  • Blocking should be carried out on a URL-specific basis and not at domain level unless a domain level URL is provided by the IWF due to the nature of the site or the distribution of content on the site;
  • We recommend the use of a specific splash page when users’ requests for web pages on the list are denied (below);
  • We subject the process of URL inclusion on the list to independent inspection;
  • We provide a robust complaints process allowing anyone to appeal against the inclusion of a URL on the list.
  • Members can opt in to our voluntary self-certification process. This allows for a Member to test their blocking system to ensure that, as far as they can reasonably ascertain, it is operating correctly from an end user perspective. For more information on this process please contact the Development Team.


The IWF strongly recommends that all relevant members serve a splash page with an agreed standard text:

"Access has been denied by your internet access provider because this page may contain indecent images of children as identified by the Internet Watch Foundation.

Deliberate attempts to access this or related material may result in you committing a criminal offence. 

The consequences of accessing such material are likely to be serious. People arrested risk losing their family and friends, access to children (including their own) and their jobs.

Stop It Now! can provide confidential and anonymous help to address concerning internet behaviour. They have helped thousands of people in this situation.

0808 1000 900 | contactus.stopitnow.org.uk/ | https://find-help.stopitnow.org.uk/

If you think this page has been blocked in error, please contact <your service provider> or visit the IWF's Content Assessment Appeal Process page."

For those wishing to address inadvertent access there is the option to add:

"If you did not intend to view this content, please close the browser page now. You can also anonymously report any potentially illegal child sexual abuse content to the Internet Watch Foundation here."

If a member is unable to serve a splash page they can direct users to an IWF landing page appropriate to their requirements:

  1. Standard text preferred as best practice;
  2. Text appropriate for serving to children;
  3. Text designed to address the welfare of the audience;
  4. Bespoke text to be developed jointly by those members requiring a bespoke approach and the IWF technical team.

The IWF strongly recommends following one of the above routes unless, following consultation with the Splash Page Working Group [#1], the member is subject to one of the following mitigating factors:

  • The member has technical issues which cannot be overcome 
  • The member would incur disproportionate costs

[#1] SPWG to be made up of at least one representative from the Board, the Executive and the Funding Council and to be convened and coordinated by the Funding Council Secretariat as required.