optimizing images for search-engines is like optimizing images for blind people. For those who haven’t the time to read the following epic article here an extract of the essential tips, in order of the importance for the ranking
- keyword the surrounding text
- keyword in the image name
- image size (min. 320 pixel, max. 1280 pixel)
- keyword in the “alt-text”
- make sure that the image is available for the images-bot
- multiple use of the image (copies)
- multiple links to the image (hot links)
- keyword in the page title (including URL)
- keyword in the title attribute of the image
- keyword relevance of the entire site
- keyword in meta description
- keyword in meta keywords
- position of page in the organic search
- new upload of the same image (“actual date”)
Unclear / changing:
- the age of the image (the older the better)
- originality (picture looks different than most of other results)
- specify images in Sitemap
Based on my experience this is it. Its about 80% of the work for a good ranking in Googles image search.
Onpage ranking factors
To be successful an image must be well embedded in the HTML page. The following onppage factors describe how to improve an image in the HTML code.
- Surrounding text: The text before and after the image should include one or more times the keyword or the keywords (of the filename). The combination of “keyword file name / keyword surrounding text ” is the lifeblood of a successful image optimization. Surrounding text means about 12 words before and after the picture. You should always look in the source code to prove. Often the code and the css-presentation are completely different.
- Alt-text: Each image should have an alt-text in the image-attribute. This is important not only for search engines, but especially for people with visual impairment. You simply have to make clear: Google is blind and can only understand text.
- Title-attribute: The meaning of the title attribute for the ranking is controversial. By specifying the title-attribute of an image by rolling-over a tooltip appears. Here the user can provide valuable information. If you have a separate caption, the title tag of the image is not necessary. I think the title attribute is a kind of surrounding text. It can increase the keyword relevance.
- Content relevance: Good content is good for images. But actually there are a lot of examples where the pages of good ranking images are lousy. I think Google will change this in the near future.