How Many Words In ALT Text For Google, Yahoo + Bing?

How many words will Google, Yahoo and Bing count as part of ALT Text on a page? Someone asked me this on the other day and I wondered if a little simple test might offer an answer. This sort of post is usually a decent way of picking up natural forum links wether it’s right or wrong….
The basic premise of course, is take an ALT tag, and put a lot of nonsense keywords in it, and see if the page will return for all (or any) the keywords. I confirmed with a similar test most search engines do count keywords in ALT text long ago.
Usefulness? I was thinking squarely from an accessibility point of view, not really spamming search engines. I think spamming ALT text can get you into trouble from what I have seen – probably depends on the site, and page, in question – or the intent.
Yes, you can use other alternatives to describe complex images, but how many words will google count in the ALT tag anyway? Is there a limit?
Here is the ALT text I tested with:

Google Results:

and

and interestingly
and
- Google seemed to count the first 16 words in the ALT tag (well.. the Alt tag is an HTML Attribute) – of the image on this page – in this instance and interestingly in the snippet Google uses it does seem to completely cut of the rest of the ALT
- EDIT – that’s 16 words of 7 + 8 characters each…. which might prove useful if you are using ALT tags to describe complex images.
- That’s potentially plenty of space to describe images properly for accessibility purposes and seo effectiveness.
If I remember I will check and add data for Yahoo and Bing.
I like doing these little seo tests just to have a poke about and see, for effective and practical best practice purposes. I have this kind of data on a lot of seo factors – I will publish here later.
NOTE: On page SEO Tests are fun but you should always test for yourself on your own site anything I warble on about. This is just one example of a page I can observe and show ‘working a particular way’.
ALSO – This is a live running test – results might differ when Google caches the page, for instance. What I am testing here in fact – is this something can be tested?!
What do you think?
Written by Shaun Anderson


Thanks Shaun, This is great. I love this stuff.
I’m now off to bookmark and retweet this.
Marjory
Shaun, very good points!
My strategy for the alt attributes is adding up to 64 characters including spaces. People should learn the difference between the “alt” attribute and the deprecated in XHTML “longdesc” tag.
Upon the chance I would like to share an article I wrote about the appropriate implementation of the alt attributes: http://www.seoworkers.com/seo-articles-tutorials/alt-attribute.html
Again, great post.
Nice test, thanks for sharing. However, I wouldn’t make a habit of pushing this to the limits. I imagine it wouldn’t be helpful for an unsighted user to have 16 words replacing every image on a page.
Of course, just because Google only displays 134 characters doesn’t mean it isn’t aware of the others (as with page titles).
Indeed I just wanted a guideline.
That is some nice data. So about 100 characters can be used. It would be nice to test short description vs. long descriptions. I suppose the long ones will get better ranking, than ppl with blindness will find the longer text more descriptive I suppose.
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