How to fully optimise an image for SEO

How to fully optimise an image for SEO


Optimising an image for SEO is not just about the alt. Text and file size, there is soooo much more.

When optimising an image you need to consider the file name, size, file format, alt text and file compression, oh and of course the relevancy and appearance that image is bringing to your website.

Let’s take a look into the different areas of optimising an image for SEO on your website!

Image Format

There are multiple image formats to use for your website, the right, it all depends on the kind of image and how you want to use it. Keeping it short and sweet, we would recommend the following:

Use JPEG images for larger photos or illustrations, this will give you good results in terms of colours and clarity with a relatively small file size on your site.

If your site is up to date it is best to use a JPEG 2000 which is an “extra optimised” image that works well for SEO if your website and server can serve this next-generation format.

  • PNG’s to preserve background transparency on your image, these can be scaled down to size and are great for mobile indexing for speed.
  • WebP produces high-quality results with smaller file sizes. You can use plugins such as Shortpixel to convert your image into WebP. These definitely are file types to look out for in the SEO world.
  • SVG files are mainly for logos and icons on your website. CSS or JavaScript, can help manage images in SVG format by resizing them without loss of quality, these tend to be quite technical so are less common.

As of recently ‘next-gen’ formats have been increasing in popularity and are likely to become the new standard for web images.

With search engines showing more importance on site performance with speed adopting ‘next-gen’ formats could be the way forward!

The JPEG 2000 format was designed to outperform the standard JPEG file for speed is definitely something not to be missed.

Both WebP and the JPEG 2000’s fresh method of compression is that it enables a single file to offer a high level of scalability, at a comparatively small file size.

Instead of having to save multiple versions of an image for different sizes, WebP and JPEG 2000 analyses what is different when the same image is displayed at different sizes.

These formats are not supported by all servers or browsers, however, you should totally watch out for that space as this will play a big role in coming SEO image optimisation!

Image Size


Once you’ve found the perfect picture for your landing page, and you know what exact file type you want, the size is the next important thing!

It’s just as important to export your image at the right size, not only for page speed but you want a decent resolution and image quality across your website.

A quick tip – Don’t export an image any larger than it will be displayed on a website. – This is just adding additional data to the file that the user will never benefit from, ie. longer loading time.)

Most images from stock image websites will download around 4000 X 3000 odd pixels, this is billboard material, not website banner worthy.

You want to resize your images from around 1200 to 1500 pixels wide to around 600 to 800 pixels tall. For images in blog posts, you can go even smaller, around 900 pixels by 600 pixels is best!

You’ve also got to pay close attention to the compression settings (quality) when you save your image.

If you don’t have access to image editing platforms like photoshop, there are many online image compression services, and plugins you can use like Smush or Tiny PNG. 500kb or half a megabyte is recommended for a solid compressed image for your website.

Oh, and avoid gifs at all costs…

Image Filename

As an SEO, I tend to name the filename the same as what the Alt. The text will be, this just keeps things tidy and boosts the image up by a keyword or so at the same time.

You don’t want to be uploading an image called “DCM-123456.jpg” or “SHUTTERSTOCK0394.jpg” It’s just messy and irrelevant for search engines to read you images. You can name the file name of the image in your windows or mac image opening tool.

Always separate the words with a hyphen so this allows search engines to separate the words as it reads them so “this-is-my-image-file-name” – Else search engines will read your image as “thisismyimagefilename” #lifehack.

Image Alt. Text


The beloved Alt. Text, what all SEO’s love! Image alt text is the crucial part of optimising an image, this is the text that tells search engines what that image actually is, as search engines can’t view images it’s best to be descriptive as possible with the keywords around that image.

Three to six words is best for an alt text description, you don’t want to write a whole paragraph in there!

If you think you need some help around how to optimise your images for alt text or need a site audit then get in touch with one of our SEO experts today!

The snap away

Hopefully, you can walk away from this post with a bit more knowledge around image file formats, sizes and optimisation! Image optimisation plays a big part in technical / on-page SEO so please don’t let that slip! If you’re interested in SEO services then say hello!