The W3C has created accessibility guidelines for websites. A is the least accessible, and puts the least constraints on the design, AAA is the most accessible, and puts the biggest constraints on the design. The W3C encourage to apply accessibility standards to non-website content also (Source).

I design a mobile app for iOS & Android and would like to pick an accessibility standard. My team and I are debating if AA or AAA are better. This will have a direct impact on design decisions, for example the choice of color. The WCAG contain minimum contrast ratios between text and background color.

On the one hand we want to be as accessible and future proof as possible, which speaks for AAA. On the other hand both Android and iOS come with accessibility features, which drastically improve accessibility independently of our color choice, which is why AA could be enough. For example, Android has a feature to increase text size.

Is it ok to say: AA is good enough, because users can increase text size with Android's built-in tool, which makes lower contrast acceptable?

My question is about this specific example (color contrast) but also the broader approach: Can we be less strict about design choices, assuming that the OS's accessibility features will improve accessibility for those who need it?

4 Answers 4


Try not to think of A as "least accessible" and AAA as "most accessible". A is the minimum set that you need to create an accessible website. There will still be some issues for some users when you're only working towards A, but A is way better than nothing.

AA makes the site accessible to more people.

W3C does not recommend trying to achieve AAA. See "Note 2" on https://www.w3.org/TR/UNDERSTANDING-WCAG20/conformance.html#uc-conf-req1-head, but there are certainly parts of AAA that are very helpful, such as 2.4.9 "Link Purpose (Link Only)"

Accessibility is interesting because trying to satisfy one success criterion might make it difficult for another user. For example, the AA requirement for minimum contrast helps people with low vision or color-deficient vision but too much contrast can be distracting for cognitive issues such as some forms of autism.

Most companies and most countries have AA requirements.

  • Interesting points. Hower, I still don't know how to decide on a standard. Any suggestions?
    – bootsmaat
    Commented Dec 8, 2018 at 9:45
  • 2
    Yes, choose AA. Legally, it's what most country laws require. Section 508 in the US is AA. AODA (Accessibility for Ontarians with Disabilities Act) is AA. The European Union EN 301 549 is AA. Commented Dec 8, 2018 at 17:23

One thing to bear in mind is that it's ok for discrete sections of the app to meet different levels -- some parts may be easy to bring to full AAA without much work, and others may be "good enough" at a lower level.

(source - I'm on the WebAIM mailing list, and a few weeks ago this came up)

https://www.w3.org/WAI/UA/work/wiki/Applying_UAAG_to_Mobile_Phones may be able to help you scan through and see which guidelines are most relevant to your app. Many of them don't even have a level AAA conformance value.


In 2016 EU Parliament approved directive 2016/2102 of the European Parliament and of the Council of 26 October 2016 on the accessibility of the websites and mobile applications of public sector bodies.

Directive aims to approximate the laws, regulations and administrative provisions of the Member States relating to the accessibility requirements of the websites and mobile applications of public sector bodies, thereby enabling those websites and mobile applications to be more accessible to users, in particular to persons with disabilities.

Requirements of directive are laid out in European Telecommunications Standards Institute's standard EN 301 549: Accessibility requirements for ICT products and services which in turn is based on WCAG 2.1 at the level AA.

Standard contains requirements also for mobile applications in the section 11.


AAA standard is hard to achieve and most of the burden on it is on the app administrators / owners, not so much on the people building the site / app in the first place. A vast amount of it comes down to multimedia content - so, for instance ensuring your video content has:

  • Subtitles
  • Alternative audio tracks (such as audio description)
  • Sign language
  • Full transcripts

Things like this mean that it's an enormous overhead to not only build a AAA accessible site / app but to keep it AAA, because with each new item of content you have to spend a lot of time optimising it.

Things like text size, contrast ratios etc primarily fall within the AA category, not the AAA.

That doesn't mean AAA is a waste of time. But it does mean it pays to be selective about whether it is necessary to meet it. If you're building an app for people with impairments / the elderly etc then yes, AAA would probably be beneficial, but in the vast majority of situations the AA standard is more than sufficient.

Also, phones - especially iOS ones - have incredibly good accessibility features built into the OS from the ground up. Provided the site / app is built to proper standards then a lot of the accessibility work will be handled natively.

  • AAA does require a higher contrast ratio than AA, see 1.4.3 and 1.4.6 in WCAG 2.1
    – bootsmaat
    Commented Dec 8, 2018 at 9:44
  • @bootsmaat yes that's true, and that's why I went with 'primarily' fall in AA. AAA does have additional requirements, but the contrast statements in AA are generally more than sufficient for the vast majority of cases.
    – JonW
    Commented Dec 10, 2018 at 11:00

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