Importance of Image Optimization for SEO
Studies have shown that content with at least one relevant image significantly outperformed content without any images. When you include images on your website, you need to optimize the images for SEO. This will ensure that you get the ranking boost that comes with using images in your content.
Search engine spiders cannot read or understand the content of a picture. You must explain what is in the image using textual content. In addition, when using images, don’t simply add an image for the sake of it. It needs to be a relevant image that reflects the topic of the post.
This is because an image that is surrounded by contextually relevant text ranks better for the keyword it is optimized for.
Optimizing for Image Search
The Image Filename
The way you name your images is particularly important, especially if you’re an ecommerce site. In order for your product images to appear for relevant searches on Google image search and in universal search results, your images have to be optimized for SEO using relevant and descriptive keywords.
Search engine spiders cannot read images, and will look for clues when trying to understand the relevance of the image to the webpage’s topic. The most effective way to increase relevance of an image to a particular search query is by adding relevant keywords to as many elements connected to the image as possible. This includes the filename, alt text, caption, surrounding text and any inbound links to the page.
For example, instead of naming your image of a Toyota Camry 2010 like this: *56001.jpg, use an SEO-friendly name such as Toyota-Camry-2010.jpg. This will help increase the on-page SEO and overall website ranking for relevant searches.
In addition, you can add schematic mark-up to your images to increase the chances of the image appearing in Google’s Knowledge Graph.
For example, to optimize an image of a red Toyota Camry 2012, you’d add the following code to your HTML: <img itemprop=“image” alt=“Red Toyota Camry 2010″ src=”http://example.com/red-camry.jpg”/>. You can also geotag the image by adding information such as where the photo was taken, what date, by whom, etc.
Given the fact that there are millions of car models, this type of naming convention tells the search engine all about the image so that you can drive people searching for a red 2004 Toyota Camry to your site. This will help increase the on-page SEO and overall website ranking of that page for relevant searches.
Adding schema to your images can be particularly useful for local businesses without physical locations in the areas that they serve. On-page optimization in the form of schematic markup is very important for ranking in those locations where you don’t have a physical address.
Captions and Descriptions
Most webmasters fail to add a caption and description to relevant images, but doing so can give your page a slight ranking boost for the keyword. A descriptive caption provides data to the search engine spiders that they can read and index. It also helps communicate your intended meaning to users.
Furthermore, including descriptive text above, below or next to the image will help increase the contextual relevance of the image. This will reinforce the relevance of the web page to the page’s topic and help increase the ranking of the web page for the keywords you use to optimize the image.
Before naming your images, it is good practice to always perform your keyword research so that your files are named according to how your potential customers refer to the most important products you sell. This may increase your chances of showing up for relevant searches.
Using Spaces and Underscores
Avoid using spaces and the underscore when naming your files. Search engines tend to view the underscore as its own character, so if you name the file Toyota_camry_2010.jpg, the search engine will interpret it as toyotaxcamryx2010, which may be difficult for some search spiders to understand.
According to Google, “Consider using punctuation in your URLs. The URL http://www.example.com/green-dress.html is much more useful to us than http://www.example.com/greendress.html. We recommend that you use hyphens (-) instead of underscores (_) in your URLs.”
Leaving spaces in the filename is also bad practice, as the search engines tend to replace the space with percentage signs. It is much better to use periods or hyphens than to use spaces.
The Alt Attribute
The alt attribute (also known as alt tags) displays what text should be shown if, for any reason, a given image is not viewable by visually impaired users and search engine spiders. Typically, when you add an alt tag to an image, try to use the target keyword of the web page to increase the relevance of the page.
In addition, include relevant text in the paragraph directly before or after the images. This will help provide search engines with further context and is what the user most closely associates with the image.
For example, if you have an image of a Galaxy s6 Android smartphone, use an alt tag that best describes the image, which in this case is “Galaxy s6 Android smartphone”.
Writing Alt Attributes
Optimizing alt tags is important to get right, and over-optimizing an alt tag could see your site penalized. Stuffing the alt attribute with irrelevant keywords would be tantamount to search engine spam, and could attract an algorithmic penalty. For this reason, it is important to ensure that you are only using your target keywords in the alt text because it is contextually relevant to the image.
Additional Alt Tag Rules
- When writing your alt tags, use keyword-rich, descriptive words.
- When writing Alt attributes for images, make the length proportionate to the image’s size on-screen.
- If your product has a product number, use this in your alt text.
- Do not keyword stuff your alt tags. For example alt=“Galaxy S6 Android Smartphone for sale. Cheapest Price. Buy Now”. This type of thing will get the entire web page penalized for spam.
- There’s no need to add alt tags to things like icons. Doing do may render the page susceptible to the over-optimization penalty.
Optimizing Your Image Dimensions
When selling a particular product on a website, it is normal to feature the product from various angles in order to increase its saleability. For example, if you’re selling a car, it is normal to include shots of the interior, dashboard, rims, engine, etc. You can capitalize on this opportunity by creating unique alt tags and filenames for each image you upload.
For example: Img src=“Toyota-Camry-2010-Black-Leather-Interior.jpg” alt=“Toyota Camry 2010 Black Leather Interior”
By taking advantage of these additional image dimensions, you will be showing up for more relevant searches, which will ultimately increase the search ranking of your site.
Optimizing the File Size
Load times are an important ranking factor. The larger the image, the longer it will take the associated web page to load, especially when you display the large image as a thumbnail.
The entire image will still have to be loaded even when it is displayed as a thumbnail. This is why it is critically important to ensure that the image file size is reduced to the lowest file size possible before uploading, while retaining quality.
A good rule of thumb is to keep your images below 70KB, especially if you have lots of images on your site. Note that even though WordPress provides the images in multiple size, this doesn’t mean the image’s file size is optimized. The file size needs to be reduced before uploading the image to WordPress.
How to Reduce Image File Sizes
There are numerous free tools you can use to reduce image file sizes:
- Squoosh.app: This is a Google web app that lets you reduce images down to smaller file sizes
- ImageOptim: This is a free tool that allows you to resize and optimize your images on the web.
- JPEGMini: This is a photo optimization application that reduces file sizes by as much as 80%.
- TinyPNG: This is a PNG compression and image optimization tool.