Note: This advice is given by the CAP Executive about non-broadcast advertising. It does not constitute legal advice. It does not bind CAP, CAP advisory panels or the Advertising Standards Authority.

In light of the ASA’s consumer research findings and public consultation, CAP announced, on 23 November 2017, that the approach most commonly used at the time was likely to mislead consumers. As a result, it has published new guidance on the advertising of numerical speed claims for residential broadband services. This guidance is now the current position, which has been in effect from 23 May 2018. The information below reflects that guidance.

The principle behind the current guidance, which also applies to mobile data services, is that speed claims must be based on consumers’ actual experience. As such advertisers should be able to demonstrate that a reasonable proportion of customers can achieve the speeds claimed.

Numerical speed claims

Advertisers making a numerical speed claims should be able to demonstrate that that speed is achievable for at least 50% of the consumer base at peak time (defined by Ofcom as between 8 and 10pm). The substantiation required for speed claims must be robust and representative of actual performance.

If there are any reasons why certain customers cannot achieve the speed stated, this will be considered material information and these reasons should be stated in the ad, for example by referring to the effects of signal attenuation on ADSL2+ services (usually translated to the consumer as “speeds will vary depending on distance from the exchange”), or by stating that a traffic management policy applies at peak times. Qualifications should be prominent, included in the body copy of the ad, and should be explained in terms easily understood by consumers.

In some circumstances, further qualification will be needed. If a significant proportion of consumers receive a maximum speed that is so much lower than the headline speed that they cannot carry out normal online activity, for example streaming content, it is likely the advertiser will need to include one of the following statements:

“X% of our customers receive speeds below YMbit/s”

“X% of our customers receive speeds above YMbit/s”

“X% of our customers receive speeds between YMbit/s and ZMbit/s”

It is for advertisers to decide the values of X, Y and Z in the examples above, and that qualification will need to be in the body copy. Obviously the inclusion of that type of qualification in an ad for an ADSL2+ service will mean there is no need to refer to the effects of signal attenuation.

As individual consumers can only receive the most accurate indication of their likely speeds by checking with the provider or a third party website, providers are advised to include a statement urging consumers to check their likely speed independently or with the provider themselves.

Non-numerical speed claims

These principles also apply to non-numerical speed claims which are likely to significantly influence a consumers expectations of the speed of the service, such as “superfast”. Non numerical speed claims will be assessed on a case by case basis.


Advertisers can gather and process data themselves, or use an independent body, providing the data supports the speed claims made. Speed claims should be based on user’s genuine experience and usage and will be assessed on a case by case basis.

The Advertising Guidance gives more information on the type of evidence needed to support speed claims.

See also Location specific claimsSuperfast and 4G claims, and the Advertising Guidance note on broadband speeds.

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