Improving site performance – using progressive JPEG images

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One of the crucial tasks in website optimization that some people tend to forget are the images. In one of our guides, we learn how to improve your website performance through scale images . This time, we go a step further and learn how to optimize baseline JPEG images progressive.

What is the difference between the baseline JPEG and progressive JPEG images?

Generally, JPEG images load from top to bottom and are called baseline images. Progressive JPEG images differ showing the entire image immediately to carry only one piece of data, meaning that it can look pixelated until it is fully charged. Below you will find an example for better understanding.

Baseline JPEG loading cycle:

basiline jpeg load

Progressive JPEG charging cycle:

progressive jpeg load

As progressive JPEG images improve site performance?

In addition to the best visual experience, Progressive JPEG images are 2% to 10% smaller in size compared to baseline images, and will improve the loading of your site and performance. Your requests to the server will be shorter and more efficient, which will also reduce the use of resources such as bandwidth and disk space. This is extremely effective if you are hosting a website hosting service free or shared sites. Sites with a lot of baseline JPEG images also will benefit greatly from the lossy compression in progressive JPEG images.

Also worth mentioning that visitors coming to your site via mobile or slow Internet connection will have a better overall viewing experience and faster load times if you use Progressive JPEG images.

IMPORTANT! Some browsers (eg Internet Explorer before Windows 7) do not support progressive JPEG images. However, all subsequent versions support.

What do you need?

Before beginning this guide, you need the following:

  • FTP access.

Step 1 – Analyzing your site

To locate baseline JPEG images that can be replaced by progressive versions, we will use . This tool is great, and you can also get the progressive version of a baseline JPEG image without using any additional tools.

Here are the results of the Performance Review section after analyzing a test site:

Prog 0 100 jpeg

Step 2 – Transfer Progressive JPEG images

There are a variety of tools to convert baseline JPEG images to progressive images. Here are a few:

Option 1 – Compression baseline JPEG to progressive use using

Once you find the list of images that can be replaced, navigate to the details ,  and then click  View all images.

view all images

This section displays all the images on your page. Press Analyze JPEG  each image located in step 1 of this tutorial and scroll to the bottom.

analyze jpeg

You will find the image quality 85  of your original image. Save all images Quality 85  on your computer and proceed to the next step. We strongly recommend you save the images with the same  name as the original file, thus the replacement procedure will be much easier.

Option 2 – Converting baseline JPEGs for progressive with Optimizilla

If you are planning to upload more images to your site in the future or if your site has not yet been sent, you can use the Optimizilla  to convert your baseline JPEG images in progressive versions. Using this tool you can optimize up to 20 images and shrink them using lossy compression algorithms for Quality 85 or even less.

optimizilla usage

IMPORTANT! Less than 85 may result in loss of quality. Proceed with caution.

Option 3 – Optimizing images with CMS plug-ins

If you have a WordPress blog, you can easily optimize your JPEG baseline images using WP Smush. Check out this tutorial  for detailed instructions on how to use the WP Smush .

Step 3 – Replacing old images

IMPORTANT! Be sure to backup your site  or images you are planning to replace before proceeding.

Using the File Manager  or any FTP client , locate the images Step 1. Remove and replace the new Quality 85  I mages  acquired in Step 2 . Again, make sure that they have the same  file name to avoid 404 errors or loading issues.

Step 4 – Testing changes

Once all the images are loaded, clear the browser cache and open your site to see if it carries well. After that, you can analyze your site with  to make sure everything was done correctly. Here are the results you should see the section details :


In this guide, we learn how to increase the speed of your site using progressive JPEG images instead of the baseline. The smoother visual experience and smaller size is sure to make you and your more satisfied visitors, while at the same time reducing the use of the site resource, improving SEO and site performance. It’s basically a win for everyone.