Karl Groves

Tech Accessibility Consultant
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+1 443.875.7343
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Longdesc – Where are the alternatives?

Non-text Content is “any content that is not a sequence of characters that can be programmatically determined or where the sequence is not expressing something in human language”. Mostly what comes to mind when discussing non-text content are audio/ video content, images, or other graphical content not necessarily image-based. WCAG 1.1.1 Calls for alternatives for non-text content. For basic images, presented in the <img> element, the ‘alt’ attribute is the most-frequent means of providing an alternative. The content you place in the ‘alt’ attribute may vary depending on the image and context but generally “…the general consensus is that if the text alternative is longer than 75-100 characters (1 to 2 sentences), it should not be considered a short text alternative and should not be presented using the alt attribute or the figcaption element…”. In the vast majority of cases, that amount of text should cover you rather well in providing a good, clear, and concise alternative for the image. But what if the image is complex? What if the information portrayed in the image can’t be described effectively in 75-100 characters? One suggestion is to use the longdesc attribute.

Historically, support for longdesc has been rather spotty. Back in 2000, WCAG 1.0 recommended using longdesc, but also acknowledged the lack of browser support and also recommended the use of what was called a D link. In practice, the D link probably saw more popularity than longdesc and its recommendation was pretty pervasive.

Over time longdesc support among user agents has improved, having been added to Opera, IE, and Firefox. Movement toward supporting longdesc has been made by Chrome’s dev team. Screen readers such as JAWS, Window-Eyes, NVDA, and Orca support it, as do many authoring tools. That hasn’t stopped the pushback on longdesc and Apple has stated they have no plans to implement longdesc.

longdesc (as implemented) is a poor solution to a real problem

There should be no argument in anyone’s mind that there’s a real issue that needs to be addressed: effective and informative alternatives to complex and/ or detailed non-text content. There are loads and loads of images on the web which convey things like charts, graphs, and diagrams. How do you describe, in 75-100 words, the components and operation of a 4-stroke engine?

Example complex image: cutaway of 4-stroke engine

Easy. You can’t. There may be other ways to describe this, such as in the same page as the image. Try getting that one past the content people. But longdesc – in its current form – is a crappy way to do this. See, the problem with longdesc is that it is basically only useful for screen reader users. Longdesc essentially locks out sighted users entirely. The image with longdesc isn’t placed in the tab order and there’s no visual affordance provided to indicate the existence of longdesc. Firefox’s implementation provides access to the long description via the context menu which is great if you knew the image has a long description, which you likely won’t if you’re not a screen reader user. As it stands, longdesc is wholly useless to people with cognitive disorders, which is another population that could seriously benefit from long descriptions.

Where are the alternatives?

Ultimately, I have to agree with many of the criticisms of longdesc. But that doesn’t mean I agree with the notion of just doing nothing, either. The fact remains that some images require longer descriptions than the 75-100 characters available to the alt attribute and despite the protestations of longdesc’s detractors, there don’t appear to be any proposed alternatives for implementing a mechanism of supplying long descriptions for non-text content, beyond saying “Fuck it, leave it to the web authors to figure that out”.

Two ideas

Unfortunately, that’s where we are right now if we want a viable means of supplying long descriptions. With Safari/ VO support out of the picture, we can’t rely on partially supported features. Or can we?

See here’s the thing about HTML: You can actually put whatever you want in your markup. You can make up your own elements or attributes, you can even add bogus values in attributes. That doesn’t mean it’ll do anything, but you can put it there. For instance, you can add the old <blink> tag to your page, but it won’t actually blink anymore in any major browser. Similarly, you can still add longdesc to your images. The attribute will still be in the attributes node of the image object. Because it is in the DOM you, the developer, can do something useful with it. Here are two possible ideas:

Dirk Ginader’s longdesc plugin places an unobtrusive icon over the image which represents a link to the long description. Activating the link replaces the image with the long description. Dirk hasn’t done much continued development on the plugin, but its a great starting point and I like the concept.

Today, I created a new Polymer-based Web Component called image-longdesc. It is basically just a different approach to my image-caption component. It places a link to the long description under the image. Remember my 4-stroke engine example? Here it is with a caption and longdesc link:

Screenshot: Prior engine example as a web component with caption and longdesc link under the image

Are these ideas perfect? I don’t know. What I do know is that we’ve yet to see longdesc’s detractors come up with any viable alternatives that address the very real need for suitable alternatives to complex non-text content.

I’m available for accessibility consulting, audits, VPATs, training, and accessible web development, email me directly at karl@karlgroves.com or call me at +1 443-875-7343