close button—Technical Requirements

Published by focuses on supporting simple lightweight websites, with an emphasis on feature phones.

the majority of people in emerging markets still have feature phones. To ensure that is accessible to all, we focus on supporting lightweight mobile websites.

There is also an emphasis on efficiency: infrastructure and data must be efficient so that operators can sustain infrastructure. This means high-bandwidth, VOIP, video and even image-heavy sites won’t be included.

So, getting to the nitty-gritty, according to, mobile websites must work without the following:

  • JavaScript
  • SVG images and WOFF font types
  • iframes
  • Video and large images
  • Flash and Java applets

Interestingly, this list reads as if it was straight out of the W3C mobile web best practices from 2006.

While some of the details of these best practices might not be as relevant as they used to be (for example, smartphones can handle more than 20KB) most of them are still sensible things to implement, even if the precise values of parameters have changed (keeping page size low is still very important and desirable, even if the acceptable limits have increased).

Let’s take a closer look.

How the Platform works

All ‘zero-rated’ websites must be submitted to and approved by If they pass the technical requirements they are ‘zero-rated’ and browsable for free.

Approved websites browsed via app are pushed through the transcoder proxy: proxy

This will have the effect of compressing and stripping assets to fit them to the user’s device.

JavaScript approved sites must work in the absence of JavaScript. The motivation for restricting JavaScript is that it may not work on low-end devices.

JavaScript is also difficult to reliably proxy-transcode (see what the proxy/transcoding browser Opera Mini has to say about JavaScript support). So another factor is that the proxy may simply not be able to faithfully work with JavaScript-reliant sites, and any such site may not work very well, or even at all, when proxied.

This is bad news for all JavaScript-rendering framework sites, as they will be excluded from participation. This means, AngularJS and ReactJS sites are going to be left out in the cold.


Sites that rely on SSL/TLS/HTTPS will not be able to participate. That is, only insecure sites will be included. This is the one technical requirement that is not really about mobile-friendliness—even feature phones have been able to handle HTTPS for years. The motivation for this requirement is that the proxy can’t work with end-to-end encryption. So the price of the proxy is privacy!


Frames can be generally problematic for mobile, and may not be supported at all on some feature phones, and so are excluded from Usability problems associated with frames can be found here.

Video and large images

This restriction is all about bandwidth and page weight. Videos and images are the heaviest components of the web, so video and image-heavy sites will be slow to load, and can clog up vulnerable networks.

Flash and Java applets

Flash and Java applets are also excluded from sites. This is because they are very unlikely to run on feature phones.


Apart from the security issue, the technical guidelines make sense in terms of making the Internet more accessible to the widest audience possible, and sites are pretty much guaranteed to run on feature phones. talks about progressive enhancement too, so experience on higher end devices is not necessarily degraded for the benefit of feature phones. Performance and page weight are top priorities, with a maximum of 1MB for resources. While this is still a bit high, the final page is being squeezed through a proxy server, so even sites with large resources will be transcoded into something more digestible anyway.

Whether or not as an initiative prevails, it’s good to see that Facebook is raising developer awareness of web performance issues. Indeed, this is also Facebook’s stated reason[pdf] for the introduction of its new Medium-like Instant Articles, although it does of course have a lot to gain by becoming the web’s default publishing platform. Still, the emphasis on performance is welcome.

More details on how to submit a site to can be found here.