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What is an 'alt tag', and why is it so important?

15th July 2015

Many website owners will have heard the phrase “search engine optimisation” a fair few times. There are many, many different elements to search engine optimisation – or SEO – that you will need to consider when managing a website, and one of those elements is an ‘alt tag’.

What is an alt tag?

‘Alt tag’ essentially means ‘alternative tag’. This is because the tag is an alternative for the image or object on the page. You will commonly see an alt tag field appear when you insert a photograph onto your page, though depending on your content management system it may be referred to simply as a ‘description’.

Why is it important to use alt tags?

Alt tags are essential for accessibility. The alt tag will be read by screenreaders and other site readers as an alternative to the image or object. They are vital for your website as they make sure that the content of your site is easy to understand and available to everyone who wants to view or read it.

Being accessible is a key SEO ingredient – if your website is not accessible, it can fail many common SEO tests and therefore suffer rank-wise.

An additional benefit is that it provides a semantic description of images for search engines to index. This can attract extra traffic through Google Images (and other image-based search engines) and will have a positive impact on your search engine optimisation – if done correctly.

However, it is important to note that adding good alt text is not going to suddenly take your website to number one on Google – instead it is one of many on-page factors that cumulatively contribute to improved SEO performance.

Things to keep in mind when using alt tags

Adding an alt tag is not as simple as just adding text describing the image – there are some key factors you need to bear in mind.

The alt text should be relatively short

In general a ‘to-the-point’ alt tag is the ideal option, though in some cases it may be more suitable to write a longer, descriptive tag if the type of image used is important to the context of the article. For example, it may be necessary to describe what is happening in the image, or label it as a particular sculpture by the person who crafted it.

Your alt tags should be precise

If your website has an e-commerce element, alt text should precisely describe the product within the image so that it shows up in relevant searches.

So for example, alt text that read “men’s red Nike Flystepper 2K3” is more effective than “men’s trainers”.

Don’t keyword stuff

Keyword stuffing is essentially putting as many of your keywords in one area as possible – this used to be quite common practice as it worked, but as Google has cracked down on unethical techniques like keyword stuffing and purchasing backlinks, this no longer works in a positive way. This should be avoided at all costs as Google can hand out pretty hefty penalties for partaking in these ‘blackhat’ SEO methods.

Hover over text is not W3C compliantCommon misconceptions

Internet Explorer 7 and earlier versions render text in alt attributes as tooltip text, which is not standards-compliant. This behaviour led many web developers to misuse the alt tag when they wished to display tooltips containing additional information about images, instead of using the title attribute that was intended for that use. Internet Explorer 8 and newer versions do not render alt attributes as tooltips.

In conclusion

That was a whirlwind tour of alt tags for your website – remember the key points listed above and seek professional advice if you’re still not too sure. You can phone our experts at Cosmic on 0845 094 6108 for more information, or even tweet us to @Cosmic_UK!