The Hidden Catch to Zero Rated UK Mobile Data on NHS Sites

Over the past few weeks all of the major UK mobile operators (O2, Vodafone, etc.) have responded to the Coronavirus (COVID-19) crisis by, among other things, zero rating (no charge) data usage on specific support websites (e.g. NHS). But this doesn’t always work as advertised and can still eat into your allowance.

On the surface it may seem easy to zero rate (no charge) data (mobile broadband) usage from specific websites, but such promotions almost always fail to highlight one big caveat. The main problem being that the content you see on a website doesn’t always come 100% from the directly associated web server or domain.

Most of the content you see when loading up a page on a website is from the same web server and domain, but many sites also have to pull in from various third-party resources (e.g. javascript / media libraries, Google code, Fonts etc.) and some articles can also feature embedded videos (e.g. YouTube, Vimeo etc.).

All of the above is fairly normal for most modern websites. Some may also involve complicated load-balancing measures via Content Delivery Networks (CDN) or additional servers and domains, which adds another dimension of “fun”. The issue is that all of these things come from different servers and domains, but for an ISP it can be extremely difficult to associate such third-party requests to a specific site.

In theory you could use Deep Packet Inspection (DPI) technology or other methods to try and identify the associated third-party content, but those can be expensive and may not work well with the modern encrypted web. Instead the most direct way is for operators to zero rate NHS and related support websites on an HTTP/SSL domain basis only (i.e. all data pulled from an nhs.uk domain is free).

In other words, while using such websites you could still be eating into your data allowance, even though operators have said you won’t. Most of the time the impact will only be small, but this may of course be more noticeable if you only had a tiny data (mobile broadband) allowance to begin with.

However, some NHS pages also embed videos from YouTube and other sources (example), which could significantly eat into your allowance, even if you load them via a zero rated site.

NHS Website Commitments by Operator

Three UK
“For those who may have health-related questions, Three is providing free data access to all NHS websites (those using the nhs.uk domain) for all customers. All calls to NHS 111 are already free.”

O2
“More than 20 websites zero-rated on O2 in addition to NHS websites.”

Vodafone
“It’s essential that people have access to the right health information. That’s why we’ve enabled all our mobile customers, whatever their payment plan, to access certain NHS websites – like www.nhs.uk and www.111.nhs.uk – without using any of their data allowance.”

EE (BT)
“All our customers can now access the NHS online without using any of the data in their plan, even if they’ve run out of their allowance.”

On the one hand we have to commend mobile operators for zero rating NHS sites as a hugely positive move, but on the other hand it would be helpful if they made clear that this won’t cover third-party content within those websites. In fairness though they’ve had to act very quickly in a crisis.

At the end of the day an ordinary internet user cannot reasonably be expected to understand the subtle complexities of how websites work under the hood, which makes this an important point to highlight as many people may be unaware (i.e. their data allowances could reduce and excess charges may in some cases apply).

The internet is, as always, significantly more complicated under the hood than may first appear. As a spokesperson for EE told ISPreview.co.uk: “Our zero rating doesn’t cover third party content due to the quantity of different resources on the NHS website. Our priority was to implement a solution as quickly as possible to ensure everybody had access to the critical content on NHS online. We worked closely with NHSX on this and our zero rating covers everything within the nhs.uk.” It’s the same for the other operators too.