Ranking on image search requires both the optimization of images and page elements to promote the ranking of those images in search, as well as optimization of images and image sizes so they load faster and improve page speed. Here's how to do it.
Image Optimization: Size Matters
The key to any coding or design endeavor is to get the most for the least. That is, to get everything you want visually with the least amount of code and the smallest size. Images are no different.
While admittedly I haven't seen a direct correlation (even spurious) between image size and the ranking of images on image search, it is a factor Google uses for page speed which is a factor Google uses for rankings.
To be clear, however, the question isn't about how small you can get your images; it's how small you can get them while maintaining the visual aesthetic. Essentially, Google doesn't want you to change your aesthetic; they want you to ensure that the aesthetic you want loads as quickly as possible.
I can't tell you here how to optimize your images, as this changes with each server and site, but here are some great resources for both testing and automating compression:
- Google PageSpeed Insights: This is the page Google themselves reference on their PageSpeed tool related to optimizing images.
- Website Testing Tools: It's a good (and short) list of some solid image optimization tools on Bryan Eisenberg's site.
- Google Image Optimization: A blog by Ryan Morben on image optimization with examples.
This is especially important for mobile where Google understands that data is slower and people are more impatient (a bad combination).
Now that you've used image optimization to help increase your page speed and improve your chances at ranking, it's time to look at image optimization from the context of ranking on image search.
Image Optimization: A Picture's Worth
A picture might be worth 1,000 words, but only if it gets seen and only if it will benefit your business to rank for image search.
Let's take for example a lawyer. If you're running a law site is it really going to be a benefit to rank on image search? Or is it more likely that ranking for images is simply going to create an environment where you have to spend your valuable time ensuring others aren't taking them without permission?
On the other side of the coin are sites that generate revenue from impressions (generally ad-based). In this case, any impression is a good impression (more or less) and you'll take traffic where you can get it. In this case it's likely worth the risk of your images being copied in exchange for the traffic.
Assuming you've decided it's beneficial for your site that you rank on image search, there are a number of areas you need to make sure to address. Let's go through some of the major areas.
If you're using stock images, it's unlikely you'll rank on image search. For obvious reasons Google doesn't want to rank multiple copies of the same image any more than they want to rank multiple copies of the same content. If you're using the same image that's been found on a hundred other sites before you, why should yours rank?
This aspect of image optimization can especially hurt online retailers who simply use the product photos sent to them by the manufacturer – the same photo they send everyone who sells their product and has been copied by everyone who reviews it. If you want to rank on image search, use unique photos.
That said, at this time (always important to add that note) Google's Matt Cutts has stated that using stock photos doesn't impact web rankings (though he did seem interested in looking at it as a quality signal thanks to the guy who sent him this question):
You need to name your images something right? If you're naming the image for your Samsung Galaxy Nexus product page (in case you went back in time 2 years) why would you name the image wpd858932702.jpg when you could name it samsumg-galaxy-nexus.jpg? And if you need a thumbnail for your image then samsung-galaxy-nexus-tb.jpg would be a good option.
Essentially you want to help Google understand what the content of the image is in any way you can. Will Google know it's the Galaxy Nexus and not the S4 in the person's hand in your image? Probably not (yet) so naming the file appropriately can help steer them in the right direction.
We all know the alt attribute is important, but many tend to use them wrong. First and foremost they are used as an accessibility tag. It defines what will appear in place of the image should it not be accessible either by mistake or choice (for example, blind people using screen readers).
The recommended maximum length of alt text is 125 characters. I tend to use as few words as possible to define the image content. Usually 4 to 6 will suffice, but sometimes more are required.
Should you use keywords? I wouldn't recommend doing so specifically, but if you're describing the picture appropriately you'll be using the words that are most appropriate for that image and thus, what it should be ranking for on image search.
Using the title element on an image creates a visual caption when the image is hovered over. There is some debate as to the value of the title tag whereas we know that Google puts weight on the alt tag. That said, it's certainly not going to hurt, it can be used to add additional visual information for your visitors when they hover over an image (and simply because something may not hold weight today, doesn't mean it won't in the future).
Google has said that alt tags should be supplemented with other tags (such as the title tag) when it serves the visitor. So this makes it pass my SEO litmus test. If it may help and won't hurt, do it.
Like everything else they do, Google couldn't make it this easy to rank your images. On top of the image-specific elements they also use the page as a whole to determine the relevancy of your image.
For example, an image from a Pinterest board with no content is less likely to rank than the same image on a full-page review of the Samsung Galaxy Nexus because Google can put the image into the context of the page as a whole and know that it's far more likely to be an authoritative and accurate image than a lone image on a page.
As the battle wages on for rankings and the standards of SEO rise (even if just that all webmasters know to do the basics like alt tags whereas that wasn't always typical) we need to take every opportunity to push the envelope and provide just a bit more to Google than the person next to you. This is where Schema comes in.
Schema markup is a lot of things, but at its core it's a set of markup that allows you to provide additional information about elements on a page (say, for example, images).
From the location, to the photographer, to the date taken, to additional description text, and much more, you can let the search engines know far more detail about what an image is and even what it's for that was possible prior to its introduction.
With so many possible uses, I can't possibly list them all here and the list would be outdated soon if I did. Fortunately the elements for images are laid out well http here on the Schema.org website. There is an example towards the bottom of that page as to how a simple Schema deployment would look. And if we think of a situation where two sites are virtually tied in how Google would rank their images, if one has Schema and the other does not, which will Google assume has the more relevant image?
Image optimization isn't a quick task. It requires time that could be spent on other things.
You need to carefully weigh the cost-benefit of image optimization and consider what impact it will have on their traffic and if that time could be better spent in other areas. This same statement applies to virtually all Internet marketing and, in fact, all business decisions. It's all about ROI, but if it fits your site traffic model, then good luck and enjoy the journey.