Additional content for your SEO, additional entry points of your site in the sections are image search engines, to advance the universal search optimization. SEO of images can increase your visibility significantly. Most importantly, it has almost nil competitor. 
But how it is exactly?
Use keywords to name your image files
The name of the image is very important. It should contain keywords related to it. We must therefore proscribe generic titles like “image1.jpg” and use the names of relevant images. Most of the search engines does not yet consider the underscore as a separator. In other words, the “_” concatenate terms and search engines consider the whole as an indivisible. However, Google consider the underscore as a separator now. Do not stick words like thecustomizewindows, opt for the-customize-windows. On the other hand, the image name is not capitalized, no accented characters without diacritic.
Note: Do not include any reference to sex, otherwise the image will be filtered by SafeSearch parental filter.
Learn how to use the “alt” and “height” tag for images
The attribute “alt” as its name suggests, the “alt” attribute specifies alternative text content. This text is considered by the crawlers of search engines. It will also be read by screen readers used by visually impaired people and the few browsers not displaying images. There must be explicit legislation. Generally, this attribute should always be informed, at least in regard to informative images. In the case of a purely decorative image, the alt attribute must be present too. This does not disrupt the Internet using a screen reader. The alt attribute must not exceed the limit of 60 characters. If these 60 characters are not sufficient to restore all the information, the alt attribute will be accompanied by a longdesc attribute. The title attribute should not be used routinely, but only when the image is hyperlinked to a specific page. This attribute must contain information describing what should happen if the image is clicked. In practice, the contents of the “title” attribute should not be identical to the title of the link. Indeed, this text also serves to visually impaired people who set their screen reader to read this attribute. Therefore, avoid unnecessary repetition. Moreover, it is recommended not to exceed the limit of 80 characters (ideally, no more than 60 characters). These two tags should not contain a simple list of keywords, but an intelligible text directly related with the image comment.
As a foot note, we wrote about importance of alt attribute in images in an early article.
NB: Do not confuse “alt” and “title”: Many believe that the alt attribute to display a tooltip when mousing-over an image and is WRONG. This confusion has been caused by the behavior of Internet Explorer. Indeed, when the user hovers over an image, Internet Explorer displays the contents of the alt attribute, when it is the role of the “title” attribute. One should keep in mind that the alt attribute must set an image as the “title” attribute to provide additional information. Moreover, it seems that the “title” attribute does nothing in terms of SEO. If you do not want Internet Explorer displays the contents of your “alt” attribute when hovering just add an attribute “title”. Microsoft’s browser will then give priority to the latter. However, this amount of effort is useful or not (as most users uses Mozilla FireFox now and Google might get confused), we have great doubt.
If necessary, add the attribute “Long Desc” tag
For WordPress, you can add the description in the description box; for hard coded pages, you have to add manually. If the image requires a long description attribute Long Desc will give further detail about the contents of the image, more precisely of the attribute “alt”, hence the name “long-desc”. All the information conveyed by the image will then be accessible to people using a screen reader.
Optimize the text near the image and its caption
It is strongly recommended to close the image with a text in relation thereto. In determining the content of a graphic image, Google scans the page text surrounding the image, the image title and numerous other criteria. They advises to optimize 7 to 10 words before and after the img tag. This will reinforce the semantic field of the image that you want to position yourself. Ideally, it should precede the image of a title in a tag of h3 or higher. Also incorporate a caption describing the image with slightly different terms from those used in the alt attribute.
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Use header tags
Avoid using the h1 tag on an image, it would be a shame. Choose a tag h2, h3 even if you can.
Allow inbound links
Try to get links pointing directly to your image link be established from the specific semantics of the image (practice more to improve your position).
Also provide outbound links
If the image used on the site is a link to another page (same site or not), it is preferable that it points to a related content, always to strengthen the positioning of your image semantics.
Check the ranking of the page where your image is inserted
More comprehensive advice, remember to check the status of the page where you insert your images optimized. Choose a page that has already indexed by Google.
Integrate each image in a tag
This may seem a detail, but some uses CSS to display their images, of course, this kind of content is not crawled.
Set your preferred picture up web pages
Google tends to count and index the images as high as possible their page and more precisely above the fold (Fold = visible area without scrolling). The fold is most often located 430px, 600px and 860px). This criterion would be took into account various Google services like Google Images , Google News , Google News Alert etc.
Limit the number of images
To promote a better ranking of an image, put little pictures on the page. Exceptions are tutorials and illustrations; they are identified by the words “how to”, “click this”, “tuts”, “tutorial”, “check” etc. or the url, tag.
Host your image if possible on the same domain as the site where it appears
An externally hosted image takes less space and can bring traffic (this is the case with deviantArt, Flickr for example) from image search engine but in terms of referencing on vertical search engines, those will come out less than if hosted in the same domain as the article.
Refer your pictures sharing sites
Share your images on sites such as Flickr or Picasa optimizing your captions and keywords.
Provide explicit paths
Create preferably specific folders to store your images. These records should contain keywords. Thus, your urls will be clear, simple and explicit.
Insert a picture that has a direct relationship to the subject matter of the page
Keep in mind that the engines improve their algorithms to try to identify the content of photos (it works well for face recognition in Google Images and in Picasa Web ). So, if you post your friend John’s picture and name it as a picture of a pig, that will be bad; but the reverse though not optimal, yet not at least dangerous: a pet pig can have a name (John in our example). But, if you want to optimize it, the name should be “My lovely pet pig John” and have a better long description. So, Google will understand you are not going to falsify John (it will obviously think John as human first!) as pig.
Target sizes of images offered by Google
Google ranks images in 3 categories:
- Small images: Up to 150 x 150 px
- Average sized images: Between 150 and 500 × 150 × 500 px
- Large images: More than 500 × 500 px
It seems to be more efficient in terms of positioning using larger images because they are generally preferred in the search results.
Remember to check the robots.txt file
You can easily check if Google does index the images on your site. Just go on Google Images and then enter “site: yoursite with extention” in the search field and search. This function displays all images linked to your site. If you see your images is appear then everything is correct. If you see nothing, this is certainly due to the fact that your robots.txt file (which can restrict the crawlers) blocks the folder containing your images. You can then add the rule “Allow: / images /” so that all image files from the folder ‘images’ are indexed.
Enable image searches from your Google Webmaster account
To do this, go to your Google Webmasters tool account , check the robot.txt from there.
Google will use certain tools, including Google Image Labeler, to associate the images on your site with labels and thus improve the indexing process and research quality images in question.
Prevent image hotlinking
Hotlinking is using the address of a file posted on a website, (usually a picture) for posting on another site. This poor practice can cause great harm since the image in question will be downloaded many times. Result: it will slow down your site and cause you to exceed your monthly quota of bandwidth (if you have so) or increse the page loading time, increase http request etc.
Provide quality images
Make sure the graphic quality of your images. By applying these tips, you will improve your rankings in image searches, but also your ranking in search engines.
