This is written specifically for WordPress websites, but the basic principles would apply to all sites. Here’s what you should focus on:
Change the name of your image file to words that people might use in a search for the content that the image is collocated with (keywords). Furthermore, it’s not a bad idea to add your organization’s name in the file name, too. For this post, I might name the image “SEO for Images Buzzquake Marketing.jpg.” It is best to rename the file before you upload it, because changing a file’s name after it is in the image library is not a simple task.
File Scale and Load Time
Keep in mind that webpage load time is a Google SEO factor. If all things were equal between two pages, the one that loads faster would receive a higher ranking in search results. Image sizes can dramatically affect load times. People sometimes use images that are inappropriately large. Ideally, the image will be no larger than needed to display properly. You would seldom need anything larger than 2500 pixels wide, and often smaller sizes would be sufficient.Keep in mind that webpage load time is a Google SEO factor. Click To Tweet
File Scale and File Size are correlated, but not completely synonymous. An image of a specific scale (2500 pixels wide, for instance) can vary in quality by a large factor. You can, for instance, have one version of a 2500 pixels wide image that is 5MB and another version of it that is 2.5MB. And human eyes often can’t discern differences in quality on a computer screen. Therefore, you can use images that are displayed at less than 100% quality to make a page load faster and get better SEO.
WordPress plugins (software), such as WP Smush, will automatically reduce images’ file sizes when they are uploaded to a site.
You can further reduce image files’ sizes by removing their EXIF (exchangeable image file format) data. In many cases, EXIF data such as geo tags are not used by a website and therefore serve no purpose other than to inflate images’ sizes.
In 2012, KissMetrics reported that “Captions under images are read on average 300% more than the body copy itself, so not using them, or not using them correctly, means missing out on an opportunity to engage a huge number of potential readers.”
Even though they may engage readers, captions sometimes tend to spoil a website’s appearance. If you think a caption doesn’t detract from a page or post, include one. If it does clutter things up, skip it. There is a slight SEO advantage to having a caption, but it is not as high as the other metadata elements (see below).
Alt text is important for 2 reasons:
- Visually impaired individuals who use screen readers will hear alt text read aloud to them.
- Google indexes the alt text of images.
We recommend that you make your alt text something similar to your image file name. When you do a Google search for images, the images you find have been indexed by Google using the alt text for the image — This is an under-exploited way that people can find your website through search.
An image with a file name and alt text that is surrounded by text containing the same terms (keyword) will rank better in search for the keyword it is optimized for.
If the page’s main keyword is Notre Dame, Notre Dame should be in the file name and alt text, and the image should be inserted on the page near where “Notre Dame” appears at least once.
Beginning with WordPress 4.4 (as of this writing the current version is 4.6), WordPress made some improvements with how it treats and handles images. If your WordPress site is not running version 4.4 or higher, it would be a good idea to upgrade your software.
Beginning with version 4.4, WordPress automatically serves a smaller size image to visitors with smaller screens (such as smart phones). The smaller versions of your images have the same aspect ratio as the originals. This makes sense. In addition to making images as small as possible without compromising their appearance, it is important to serve appropriately sized images based on users’ screen sizes. There’s no sense in downloading an image that is wider and taller than the screen! Fortunately, WordPress will do this for all images. There is no need to make any changes to legacy content.
Please note that if a visitor is using an older browser, it may be incapable of making use of the improvements that WordPress 4.4 affords, and therefore, a larger image will be served as before. With this in mind, it is still important to optimize your images as described above.