No content flashes more than three times per second

To make websites as safe as possible for all users, you must limit the amount of flashing media. Flashing content can harm the health of some users.

What this means

Don’t add anything to your website that flashes more than three times a second.

Tips

  • This builds on Guideline 2.3.1 by removing an exception that I recommend you ignore anyway.
  • Remember, flashing is different to blinking (see Guideline 2.2.2).

See also

Save user data when re-authenticating

It may be essential for your users to re-authenticate their identity for certain functions. For example, you might set a login to expire after a certain amount of time in case a user leaves their computer unattended in the middle of a purchase.

While your website will rightly use this function for your users’ security, you can help your users by saving all information entered by the user. When they re-authenticate (such as logging back in) you can display whatever data they had already entered.

What to do

  • When you ask a user to re-authenticate their identity, the user can continue exactly as before with saved data (for example, their shopping basket contents, input into forms or accessibility options).
  • Things like surveys and questionnaires can be saved and completed at a later date.

Tips

If you do ask your users to re-authenticate after a certain amount of time, consider whether your use of a time limit is justified under Guideline 2.2.1 and Guideline 2.2.3.

See also

Don’t interrupt your users

Some of your users will have difficulty maintaining their focus and attention; interrupting their experience may impact their understanding of your content. You can avoid this by eliminating interruptions.

What to do

  • Don’t use an automatic redirect or refresh function based on a time delay (for example, if a webpage has moved, do not redirect users to the new page after a certain amount of time).
  • Provide an option for turning off all but ‘essential’ interruptions (see below).

Tips

The best thing you can do is eliminate all interruptions by default. Allow your users to interact with webpages naturally and don’t try to surprise or manipulate them. If you can’t capture your users’ interest without a pop-up, you have bigger problems than Level AAA.

If you must use a pop-up, make sure that keyboard focus is on the window-closing ‘X’ icon in the corner that closes the pop-up. This means keyboard users can close the new window. When they do close it, return focus to the place on the page they were at before the pop-up appeared.

Exceptions

Warnings about a user’s health, safety or the security of their data or property as they are considered ‘essential’ (I’m not sure how a website would know if your house was about to explode, but let’s not ban it from trying to tell you!).

See also

 

No time limits on your website

If any of your content is time-controlled, you risk losing users who need more time to read and understand the information on your website.

Time-controlled content is anything on your website that expires or becomes unusable by your users after a certain time. A common example is giving a user ten minutes to fill in and send a form. There are functional reasons to set time limits, but you must consider all of your users.

What to do

This guideline builds on Guideline 2.2.1. That guideline (at the lower Level A standard of compliance) requires you to offer users a chance to turn off or extend time limits. At Level AAA, this guideline requires that you do not set time limits at all (with two exceptions below).

Exceptions

You can set a time limit if:

  • The time limit is due to real-time events, like bidding in an auction.
  • Your content is a live video stream.

See also

Your website is accessible by keyboard only, without exception

Your users have varying degrees of motor skills and may use your website with only their keyboard. Users with motor impairment, including many elderly users, need help to navigate your website.

All parts of your website must be accessible by keyboard only. That means, without a mouse or pointing device, your forms, menus, shopping cart and everything between. On top of that, you cannot require specific timings for keystrokes to access any feature.

What to do

A clean HTML and CSS website will often have keyboard accessibility without further work. This is a great example of why you need to invest in web design and development from the outset.

Tips

  • Unlike the lower-level Guideline 2.1.1, there are no exceptions here. All aspects of your website must be accessible by keyboard. It’s up to you to decide if Level AAA conformance is worth you removing any mouse-only features.
  • Unplug your mouse and make sure you can fully use your website with your keyboard.
  • Make sure no function on your website requires timed keystrokes (for example, ‘ double tap on enter within two seconds’ to submit).
  • Don’t use ‘access keys’ (assigning a navigation link to a particular key) or page-specific key commands as they can conflict with assistive technology.
  • Be wary of third-party adverts and widgets, often these are not accessible.

See also

Don’t use images of text

Some of your users will visit your website using a text-only browser, or might have images turned off in a regular browser. Images of text cause problems, as they are harder for those users to understand.

Images of text also cause problems for your users if they like to resize websites to read them more clearly, because images do not work well this way. They also add to the time it takes your website to load, another key reason users will leave your website.

What to do

  • Don’t use an image of text when you can use plain text.
  • Display quotes as text rather than images.
  • Use CSS to style headings.
  • Use CSS to style navigation menus as text.

Exceptions

Despite the title of Guideline 1.4.9, some exceptions allow you to use images of text on your website:

  • Brand logos.
  • If using an image of text is essential because you can’t achieve the effect with text (for example, presenting a particular example of typography).
  • If the text is purely decorative.

Tips

  • You may already comply with this guideline, depending on how you addressed Guideline 1.4.5.
  • Images of text are subject to guidelines on colour contrast. See Guideline 1.4.3 and Guideline 1.4.6.

See also

Offer users a range of presentation options

Some of your users will have difficulty viewing your website with the same clarity as others. There’s no way you can guess every combination of colours and sizes your users prefer, but you can offer ways for them to customise their view.

Allowing your users to select from a range of visual presentation options will help them to get the best from your website.

What to do

The following five features are cumulative, as all must be in place to pass Guideline 1.4.8:

  1. Provide a tool that enables your customers to select from a number of background and foreground colours; and
  2. Text blocks must be no wider than 80 characters (make sure resized browser windows do not need horizontal scrolling); and
  3. Text is not justified to both sides of the webpage; and
  4. Provide a tool that enables your users to select from a number of line and paragraph spacing options – one of the options must give line spacing that is at least 1.5 in text blocks and spaces between paragraphs are at least 1.5x line spacing; and
  5. Text can be resized in a browser up to 200% without requiring the user to scroll horizontally (you may have fulfilled this when you complied with Guideline 1.4.4).

Tips

  • The W3C’s in-depth colour picker will cover feature number 1 noted prior.
  • The BBC’s accessibility page has a good range of colour and spacing options.
  • Add all visual presentation options to the header of your website, so they are some of the first things that your users see.

See also

Your audio is clear for listeners to hear

Some of your users will have difficulties with their hearing. They will not be able to hear your audio content as clearly as other users. You can help by ensuring that all of your audio is clear.
If you have pre-recorded audio-only content, keep background noise to a minimum so that the speaking voices can be heard.

What to do

  • Make sure your pre-recorded audio does not contain any background noise; or
  • If there has to be some background noise, it is generally 20 decibels lower than the foreground noise. That’s about four times quieter.

Tips

  • Record your audio in a place you know will be quiet (a room with lots of soft furnishings is best if you haven’t got a studio).
  • Embed good quality audio (you should be doing this anyway if you care about your website).

Exceptions

Background noise is acceptable if:

  • The audio isn’t mainly speech (for example, in an audio play, an action scene might have a helicopter blown up by a car).
  • The audio is part of a CAPTCHA element (CAPTCHA is a test that separates humans from spam bots and is often used in forms).
  • The audio is you singing or rapping.

See also

Contrast ratio between your text and background is at least 7:1

All of your users will benefit from a good contrast between the text on your website and the background colour. Some of your users with visual impairments need a stronger contrast than others, so getting your colours right is essential.

While the minimum contrast for Level AA was 4.5:1, for Level AAA it’s 7:1. This higher level of contrast makes it even easier for everyone to read your content.

What to do

Make sure the contrast ratio between your text and background is at least 7:1.

Do this by:

  • Using a light background and dark text; or
  • Using a dark background and light text; and
  • Using a colour contrast checker to verify your choice.

Tips

  • You may have fulfilled this guideline when you complied with Guideline 1.4.3.
  • Remember to ensure that all colours used conform. This includes links that change colour after being used once, and headings in menus and sidebars, as well as main content.
  • Make sure that any embedded charts or images of charts have the minimum contrast between elements (for example, bars, axes and labels).
  • This guideline also applies to images of text (but you shouldn’t be using images of text – see Guideline 1.4.5).

Exceptions

  • Text that is 18 points or larger (or 14 points or larger, if bold) must have a contrast of at least 4.5:1.
  • Where text is purely decorative – so you could have a block of different coloured words on a blue background if it didn’t mean anything to your users and their order was random.
  • Where the text is an incidental part of an image (for example, a man who is reading a newspaper or a landscape that happens to include a street sign).
  • Brand logos.

See also

Provide alternatives for live audio

When broadcasting live audio-only content, such as a live podcast or radio stream, some users will rely on an alternative to the audio to understand your content.

What to do

  • Add closed captions to live audio; or
  • If the live broadcast is from a prepared script, make the script text available from near the original content.

Tips

  • To add live captions to an audio broadcast you will need professional software.
  • You may also want to hire a professional subtitler to get the best results.

See also