I recently did a little research on how to properly optimize website images with and complied the best practices I found on Moz, Google and Shopify, with additional links for more information at the bottom of this article :)
Use detailed, informative file names
Utilizing a client’s chosen keywords in image file description names is a good way to boost a site’s visibility and rankings when people search for those keywords. For example: renaming an image 2012-Ford-Mustang-LX-Red.jpg, rather than keeping it DCMIMAGE10.jpg, if building a site for a car dealership.
Utilize descriptive, keyword-themed alt tags
This is the #1 priority when it comes to SEO for images. In addition to utilizing descriptive file names, having descriptive alt tags (that describes exactly the content of the image) allows for greater visibility and higher rankings for a site, especially for E-commerce sites with a lot of images.
Tips/Rules when it comes to alt tags:
- Describe images in plain English, just like with file names.
- For E-commerce sites, if there are products that have model numbers or serial numbers, use those in the alt tags.
- Do not keyword stuff alt tags. For example: alt=”ford mustang muscle car buy now cheap best price on sale,” as this may make search engines think a site is spam.
- Don’t use alt tags for decorative images. This may make search engines penalize a site as well.
Google Source – https://support.google.com/webmasters/answer/114016