In our previous articles, we’ve helped you optimize the title tags, meta description and even urls for your SEO. Now we are going to help you optimize the images and in particular the ALT attribute of them.

Visual content is essential, but it cannot stand out from textual content because Google does not interpret images yet. When its robot goes through a page of your website, it "understands" only the words, indications of the HTML code. Therefore, an image which doesn’t have a name does not exist in the eyes of Google. This is where the ALT tag really plays its full role because it lets you indicate what an image corresponds to.


The ALT attribute in a nutshell!

Defining an image’s ALT attribute

The ALT tag, or more accurately the ALT attribute, lets Google know what an image is.

It corresponds to a part of the HTML code of a page, but don't panic! You don't need to know how to code for all that >> all CMS like WordPress, Magento, Shopify, etc... show you an ALT field to be filled in when importing each of your images.

alt definition tag

Example of an image import on WordPress with ALT attribute

If you then want to verify that these attributes have been set up, you can analyze your HTML content or use SEO software. For example, on SmartKeyword, we allow you to analyze whether your tags are correctly indicated using the "Work this keyword" tab (“travailler ce mot clé”).

What is the alt tag?

Example of checking for the presence of ALT attributes of images on SmartKeyword

Thus, you can directly know which images do not contain an ALT tag and go to your CMS software to modify this.

Why is this important in SEO?

  • Optimizing your ALT tag means optimizing your SEO, the keywords contained in the ALT are taken into account for search engine positioning: this attribute helps Google to contextualize your content.
  • Universal research is increasingly important. Referencing your images on search engines therefore becomes essential to be visible, and this can generate traffic to your site via Google Images, for example.
  • The ALT attribute is orally read by the screen reader for the visually impaired.
  • This will be the content displayed if your website is slowed down by some problem (server, slowness ...), which therefore makes it clear that this is supposed to indicate to the user what should be found instead of this image.

How to optimize images for SEO?

  • Define the image's ALT tag by describing your images in plain English and keywords you want them to show up in search engines.
  • And concretely: choose between 5 to 6 key words which will describe what your image represents. The idea is to present its content and function.

Example: for the image below, “group cooking lessons” or “group cooking lessons”.

how to properly reference an image?

It's hard to talk about image optimization without talking about:

The Image's size

Also be careful not to take too heavy images to avoid slowing down the loading time. In theory, an image should not exceed 200KB. When a page takes too long to load, search engines spend too much time on it (to the detriment of your other content), and you have a greater chance that the user leaves your page. You have the option of being able to compress your images with plugins like wp smush for wordpress, or Optimzilla to easily compress images.

alt image tag optimization

Title attribute

The TITLE attribute is the text which appears when you place the mouse over the image. This text is not taken into account for positioning in Google and is therefore not very important in SEO: however, it may be interesting for your users, so fill it out!

The caption

Ideally all of your images have a small caption that describes the image in slightly different terms than those used for the ALT attribute. Again, this will help Google contextualize your image.

The file name

It is made up of keywords related to the image. Please note: no "_", no upper-case letters or accented characters.

How to set it up?

The ALT attribute is a part of a page's HTML code that is easy to fill out. We don’t necessarily need to know how to code, CMS such as WordPress tell you an ALT field to fill in for each of your images on your website.

So if we take the example of WordPress, the ALT tag of your image will be under the name "ALT text". If this field is empty, be aware that it is important to complete it by giving it a title corresponding to the content of the image.

image optimization alt seo attribute tag natural referencing

Optimizing your images requires some work in order to be done correctly. However, this investment will benefit you for your positioning and natural referencing. Do not neglect this important textual element, because it is a set of efficient SEO practices that will promote your possibility of being on the first page of search engines!

Mistakes to avoid

  • Do not confuse the alt and title attributes.
  • Avoid images with text because the text in the image will not be indexed by the robot, instead favor keywords.
  • An image header, sites often give the option of having an image header or even a logo. To avoid! The header is one of the most important areas of your website where you should instead integrate your main keywords to optimize your SEO.


Now you know how to set up your ALT attributes, you can optimize them with Smartkeyword!

   Article written by Louis Chevant

Further reading

The complete Guide to On-page SEO

All the rules to optimise each page element at best.