Optimizing Image Tag Alt Attributes: Good Use and Abuse

Thursday, 8 May 2008

I recently went to the Amazon website and as I landed on the homepage, I noticed a large amount of text that appeared while the main image was loading (image 1)... After looking at the source and cache version of the page (image 2), the text was actually included in the alt attribute of the image tag.

Nothing amazing about this! What surprised me however, is the amount of content in the alt attribute... not a few keywords, not a few sentences, but an entire paragraph of text!
I assumed that the alt tag had to be descriptive, accurate and short and therefore I was not expecting this from Amazon and therefore decided to investigate the topic in further details.

Image 1:
Amazon SEO - HomePage
Image 2
Amazon SEO - Cache


About using a Alt attribute in your Image tag


As per the W3C Web Content Accessibility Guidelines, it is recommended to provide a text-equivalent for every non-text elements in case some of the users have visual impairments or if users have the image display turned off on their browsers.
Matt Cutts from the Google Web Spam team, has recommended in one of his video, to use the alt attribute of the image tag and the Google Webmaster guidelines also consider the use of the attribute in the development of a search engine friendly websites. The reason behind this is that search engines spiders are not able to 'read' the content in your image.. and therefore cannot index it without a text equivalent.

How to use the Alt attribute: Who should you trust?

Even if the alt attribute has only a moderate importance in the search engine algorithms, optimising them can have an impact on search engine rankings especially if you want to target the long tail of searches with content-poor pages.
I did some research and found a large amount of really basic information on how to optimize the alt attribute. But quite surprisingly, I came across mixed messages on how to 'properly' use the alt attribute:
According to the W3C, the content in the alt attribute should fulfills the same function as the image. On the other hand, Google Webmaster Guidelines quote that the alt attribute should be used to describe the contents of an image file.

This is quite confusing: Should we focus on the description or the function? In theory it does not seem to be a big deal, but in the practice, such confusion can lead to very different uses of the alt attribute.
Lets take the example of the image on the Amazon homepage:

Following Google's guidelines, a proper alt tag could be something like: Letter from Jeff Bezos annoucning the new products and services available.

Following W3C's recommendations, the function of the image is to inform customers that new products are available and therefore the alt tag should basically contain the entire text (what Amazon did). (Note: To be fully compliant with W3C guidelines, Amazon should have included a short description in the alt attribute and the entire content in a longdesc attribute, but let's not talk about this now)

Who should we trust? Google? the W3C? Yourself and your common sense? I would probably say a bit everything. As Google is the dominant search engine, you do not want to alert their spam filters (might have some) with some long or improper alt attributes.
If you are a leading website you also want to make sure that users with disabilities will be able to understand your content and therefore it is probably better to focus a little bit more on the function of the image rather than the description.
Moreover, the decision you make on how to use the alt attribute also depends on the type of image you have.
In the case of Amazon, providing a simple description of the image will be quite frustrating for a blind user as they probably wants to know what is in the letter instead of knowing that it is a letter (Still do not understand why Amazon did not use pure text for that ???)
For more practical examples and resources on alt attributes consult the NASA Section 508 website

Optimizing Alt Attribute: Good Use and Abuse

While there is no clear guidelines, I have tried to summerize some of the good practices and bad practices I have noticed in my research. It is probably not the absolute truth, but these recommendations should help you to optimize your alt attributes correctly:

- If the image is used for layout/design purposes should have empty alt attribute (no space between the ""). Using irrelevant keywords in spacers or layout pictures is an abuse.

- If the image is used for navigation purposes, it MUST have a alt attribute that match with the keyword used in the image. Alternatively it should describe the linking page accurately. To avoid any issue, make sure you use the same term in the alt and image.

- If the image is used as a link, you should also have a alt tag equivalent to the title of the linking page. The content in the alt attribute of image links is usually regarded as more important.

- If the image contains a lot of text(e.g Amazon), use the text from the image in the alt attribute. For this one, I would be careful though! If the text is too long, it could risk to look suspicious, so I would advise to offer a summary or to use a longdesc attribute. Alternatively why using an image when you can use text ??

- Do not just stuff a list of comma-separated keywords in the alt attribute, try to make a sentence that describes the picture/function and includes some relevant targeted keywords in it. You might not be able to use all your targeted keywords in the alt tag of the same image, that is fine, you probably have more than one image.

- For individual product pages in E-Commerce stores, I would recommend to use the product name as the alt attribute of the product image. That will help ranking for the product name phrases.

More tips from W3C

31 Comments:

design said...

Great article. To my mind the important thing to remember is that Google is trying to reward good quality websites. In some cases, an image would warrant a very long description.

For example: An art review website might have a discussion on a particular painting, without actually describing the painting. In this case a lengthy description of the painting in the ALT tag would make perfect sense.

I'm looking forward to the debate. Google Vs SEO community: "Is a picture worth 1000 words?" ;-)

Tristan Boyd

seo sydney australia said...

A grey area in SEO, for sure. Clearly ALT tags have a an effect on SEO. Though as Tristan points out, will an ALT tag be worthy of a lengthy listing, or will it be tagged as spam?

I'd assume that Google will allow anything up to 200 words before they'd look at it as spam.

Anonymous said...

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IMISSMYJUNO said...

Bargh, ALT is not a tag, it's an attribute!

Anonymous said...

Yeah it is an attribute that is what the entire article says! (except the image)

Book_keeper said...

i put 5-8 keywords in 1 image tag alt, do you think google would find it as a spam?

Alban said...

5-8 keywords seems alright to me. What is the most important is not the quantity but the quality.
In other words, we can many keywords as long as they describe the image accurately.

PixelShots said...

hi, am a bit confusd.. am a photo blogger and ma images are not for navigation or design.me used to give just the name of the photo into the alt tag thinking more than one keywords or names can't be given in alt.. reading your article gave a different perspective..

you saying to describe the image in a sentence, oh won't be there a limit for the crawler to take this much characters only like it does(40 charcters) on the title permalinks of blogger....hope you may have a litle time to check the alt in ma blog images and give me an advice..

cu friend..thanx for the info

www.pixelshots.blogspot.com

John said...

I've had a similar discussion with multiple clients, some on multiple occasions. IMO, there are more important areas than ALT tags that merit our SEO focus, and spending a lot of time on them is probably not worth it. A couple of keywords sprinkled in a sentence is appropriate. I frown on keyword stuffing because I do think it hurts usability for those who are visually impaired - this is important for B2C sites and perhaps not so much for B2B sites.

Anonymous said...

Buen artículo, excelente

Carlos Colpas

Anonymous said...

On an e-commerce site with, say, 10 detailed images per product -- can naming the alt tag with the name of the product cause them to be seen as duplicate content?

Alban G. said...

If you have 10 product images with the same alt attribute,it might be a little bit too much. It won't be a duplicate content issue, but might look a bit spammy.
I would suggest to optimise the main image alt attribute and the second image with a varition of the product name, and this should be ok.

As a rule of thumb, you do not want to push it too far:-)

Anonymous said...

good article i own a dj mix site and i want to add alt attributes my dj mix listings pages can have upto 50 images per page if they all have the same keywords will this be to spamy

Alban G. said...

If 50 images have the same ALT Attribute, it would be spammy.

You might want to use relevant images on your pages and describe them accurately within the ALT Attribute rather than using the exact same keyword. Alternatively, you might want to add a bit more text...

Arvind Chayal said...

Nice Post.
Thanks For Sharing Nice Info With Us

Canvas Prints said...

I really think alt tags should be a 1 sentence thing. To the point and a descriptive representation of the image itself.

Great post

Purple Lattice said...

Good Analysis. I do agree that one have to be careful when altering the images for the site. yes, the images likes Spacer, dot, breadcrumbs etc would not be alt tagged. While navigation images should labeled with the corresponding landing page's related keywords...

Anyway good article on the topic.

Thnx.

Anonymous said...

Hey,

This is a inquiry for the webmaster/admin here at www.seosydneyblog.com.

May I use part of the information from this blog post above if I give a link back to this website?

Thanks,
Alex

Anonymous said...

Thanks for sharing the link, but argg it seems to be down... Does anybody have a mirror or another source? Please answer to my post if you do!

I would appreciate if a staff member here at www.seosydneyblog.com could post it.

Thanks,
Alex

Anonymous said...

Have you considered the fact that this might work another way? I am wondering if anyone else has come across something
similar in the past? Let me know your thoughts...

Anonymous said...

Thanks for sharing the link, but unfortunately it seems to be down... Does anybody have a mirror or another source? Please reply to my post if you do!

I would appreciate if someone here at www.seosydneyblog.com could repost it.

Thanks,
John

Alban G. said...

Hi John,

Sorry mate, but they must have changed it.

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Photos on canvas said...

In reality their SEO benefit is limited so it's best to adherd to the standards and use them as descriptions of the images.

Eonic WPM said...

Doesnt making the description long water down the potency of a keyword?

Michael said...

Wont making the description too long water down the potency of an alt tag keyword?

Eric said...

I run an image based blog and I usually just put a few words in the alt attribute to describe the pic. I don't use sentences mainly because my blog is just funny pics so I have duplicate tags. As of yet I haven't had any problems with Google. We'll see what happens. Thanks for the info.