Keywords in the filename
Search engines such as Google look to keywords in the URLs of web pages as indication of what the site is about. Similarly the title of an image uploaded unto a site can indicate to the search engine what that image is about. Name the image something short and obviously related to the image for best results.
Alt tags or alternative text is another way in which search engines can establish what an image is about. Search engine crawlers cannot interpret visual information - they are essentially 'blind'. The only way for these bots to 'see' an image is to read the text that surrounds it. This includes text such as the filename, alt tags as well as any captions included. It's important to make sure that alt tags are succinct yet descriptive - you want them to pop up in search results related to your targeted keywords.
Image Title tags
The image title tag is displayed on mouse hover in many browsers and can provide additional information to users.
So, anywhere you have images which are suitable to have alternative tags, you should add an image title tag also. The title tag should ideally not be a copy of the Alt text, rather it should match it. Keep the title tag short and don't just list your keywords in it, create a meaningful sentence that relates directly to what the image is about.
Anchor text is another SEO
tactic that gives the search engine crawlers a clue as to what your images are about. Some content producers choose to link to an image in their text body rather than including the image itself. If you choose to do this it is essential that the anchor text the image is linked to is related to the image you are linking to. For instance linking to an image of an apple with the anchor text "image" does not really give us an indication that the image is in fact that of an apple. By matching up your anchor text with your image you'll create a better user experience as well as improve your site's SEO.
Avoid keyword stuffing
Keyword stuffing is an iniquitous SEO practice (often found in Black Hat SEO practices
) that attempts to literally stuff keywords into tags and file names. However this tactic is frowned upon by Google and other search engines and will most likely relegate your pages to the back of the search results. While keywords are essential part of optimising any site or its content - stay relevant and true to the context in which the keyword is found.
Image matches content
Relevance is key when it comes to optimising for images. Make sure that your image matches your content and aligns with all the other elements for which you have optimised such as alt tags, image URL and filename. Remember, relevant content shows Google that you are not setting up random, spammy websites and that your content
is of a good quality and standard.