Day 5 of the bigmouthmedia SEO Advent Calendar. You can read day 4 here.
Basics of Image Search Optimization
Optimising images for search is an often overlooked way of increasing traffic and exposure. The basics of image optimization are simple and mostly focus on making sure that Search Engines are confident that they know what an image shows. These simple tips will help you to ensure that your images are indexed and rank well for your chosen keywords.
The filename is probably the most important factor when it comes to image optimisation. A filename such as 2947859.jpg offers no information about what the image shows so use a descriptive filename containing the main keyword. As with URLs best practice is to separate words using hyphens, for example devon-blue-cheese.jpg
An Alt Text should describe the image to those who cannot see it (for example Search Engine Spiders and visually impaired people using Screen Readers). The Alt Text should be clear and descriptive for example alt=”A Wheel of Devon Blue Cheese”
The text surrounding an image is a key factor used by Search Engines to determine what the image shows. When optimising an image for search ensure that the copy surrounding the image is on-topic and keyword rich.
Adding a clear, descriptive caption below an image will ensure that it is surrounded by relevant text. The caption doesn’t need to be an exact description of the image, for example it will often reference the photographer. The caption should be contained within the same HTML container (<div>, <p> etc.) as the image in order to be associated with it.
As well as optimising the text around an image you should pay attention to other on-page factors. For example use the keyword you are hoping the image will rank for within the page title. If a Search Engine can ascertain that a page is about cheese then an image on this page will be more likely to rank for cheese related terms.
Creating an image Sitemap (or adding images to your main Sitemap.xml) will help to ensure that your images are discovered by Search Engines.