Step-by-step guide to install and use ShortPixel Adaptive Images (SPAI)

In this guide, you will see how you can install ShortPixel Adaptive Images (SPAI), an explanation of its settings and how to know if SPAI is working well, and if it isn't, how to solve it. Let's go!

Installing ShortPixel Adaptive Images

There are 3 ways you can install SPAI, and they are the same as with every other plugin.

Install SPAI using WordPress Plugin Search

First thing you need to do is go to your WordPress admin area and click on  Plugins > Add New. Then, write on the search field "shortpixel adaptive images".

Now, click on Install Now on the ShortPixel Adaptive Images box. The button will change to Activate. Click on it and that's it!

Install SPAI using the WordPress Admin Plugin Upload

You can also download an upload the plugin, if you don't feel like using the plugin search. First, go to the plugin page by clicking here and download the plugin.

Go to your WordPress admin area and go to Plugins > Add New > Upload Plugin
Click on Choose File, look for the .zip that you just downloaded, select it, and upload it here by clicking on Install Now. After activating it, that's it!

Manually Install a WordPress Plugin using FTP

The 3rd way, which is for experienced users, is to download and upload the plugin via FTP. First of all, follow steps 2a and 2b.

Now, extract the .zip file on your computer. Extracting the plugin .zip file will create a new folder with the same name. This is the folder that you need to manually upload to your website using a FTP client.

Open the FTP client on your computer and connect to your website using the login credentials provided by your web host. Once connected, you need to access the path /wp-content/plugins

Next, upload the folder you extracted from the .zip file to the /wp-content/plugins folder on your web server.

After uploading the files, you need to visit the WordPress admin area and click on the  Plugins link in the admin menu. You will see your plugin successfully installed on the plugins page.

And you need to click on the Activate link below the plugin.



Associate your website to your ShortPixel Account

Please note that ShortPixel Adaptive Images does not require an API Key to start working. You only need to associate your website/domain to your account so that your ShortPixel credits will be used.


ShortPixel is very easy to use; you just need to take a look at its Settings to see that it's anything but complicated. To access, just log in to your WordPress admin area and go to Settings > ShortPixel AI.

Under the General tab, we see the following.

  • Compression level: check out this article to know more about it.
  • WebP Support: WebP images are the next generation of images, specially designed for the web. In short, WebP images are 26% smaller in size compared to PNGs and 25-34% smaller than comparable JPEG images. Here is more information about them. ShortPixel offers you the possibility to have WebP support with just a single click. We recommend you to activate this setting unless you know you will have some compatibility issues. You can check the browsers that support this image format here.
  • Fade-in effect: In order to work properly, SPAI lazy-loads the images. This means that they won't be loaded until they are needed, which is when they will be visible on the user's screen. In order to make the transition to visible smooth, SPAI fades-in the images, but if for some reason you experience problems with images with special effects, try disabling this option.

Under the Advanced tab, we find this:

  • API URL: you can make SPAI work with your own CDN, and this is the field to configure. Do not modify it unless you know what you are doing. For more information about this, check this article, and if you are using StackPath as CDN, check this article too.
  • Replace method: this modifies how SPAI will replace the images with the optimized ones (remember that SPAI changes the URL of the image).
    • SRC: this is the recommended method. It makes sure the images remain only with the SRC attribute which resizes to the placeholder.
    • BOTH (experimental): it does the same as SRC but it also keeps the SRCSET attribute while replacing images in it (but not resizing them).
    • SRCSET (experimental): it only replaces images in the SRCSET attribute.
  • Excluded selectors: here you can write the CSS selectors you want SPAI to exclude. If you write them on the left side, SPAI will optimize such images but not resize them. If you write them on the right side, SPAI will completely ignore them, no optimization nor resizing.
  • Excluded URLs: if you want SPAI to ignore some of your images, this is where you exclude them, using regular expressions (to exclude all GIFs or all PNGs, for example) or paths (to exclude a single image, for example). The plugin includes already a good explanation on how to use this field, make sure to check it out!



The first question that comes to mind is: "Is SPAI working well on my website? You can find out while reading this article!

We also updated our knowledge base with many articles that will help you out when something is not working as expected:

  • First of all, check out this one, it is a "general" one that will explain you the most common reasons of malfunctioning. 
  • If you notice that no images are served via ShortPixel CDN this article helps you debug everything yourself, step-by-step.
  • Are you using GTmetrix? Do you get a message saying "Specify a cache validator"? Then read this.
  • Do you use the Developer tools and your images appear as data:image/svg? Then read this.
  • SPAI is not serving the WebP images correctly? Maybe it does!
  • Do you get a 500 error when installing the plugin? Make sure to read this.

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