Progressive JPEG

Progressive JPEG images are used everywhere these days. Optimus also creates progressive JPEGs as output. But what’s the difference between progressive and regular (baseline) JPEGs?

Progressive JPEGs vs Baseline JPEGs

Normally JPEGs will load from top to bottom, these are known as baseline images. Progressive JPEGs are different in that they show the entire image right away, but only load some of the data, meaning it might look slightly pixelated until the image fully loads. You can see examples below.

Baseline JPEG Example

baseline JPEG

Progressive JPEG Example

Progressive JPEG

The benefits of progressive JPEG images

Depending on the file size, progressive JPEGs can be much better optimized, resulting in a smaller output size (leading to faster load times). Modern browsers can display JPEG images more quickly if they were created using a progressive method. Safari and IE 8 are not compatible with the advantageous compression and display these JPEGs at regular speed (meaning without a performance improvement) within a website. In this context, it is important to note that something is shown more quickly to the reader when using progressive JPEGs, as the image changes from a rough to a high-quality display.

At you can find a convenient tool for you use that shows you whether images are progressive JPEGs. It can easily be tried out by comparing JPEG images to each other before and after uploading them to WordPress while Optimus is activated.

More links on the topic of progressive JPEGs:


  1. Firman Herdiansyah

    I Use Optimus on my website, but when check at all my images not use Progressive JPEGs. Any aditional setup to work with this?

    1. Cody Arsenault

      There is nothing you need to define in order for Optimus to create the progressive JPGs. However, have you double checked that Optimus was able to optimize all variations of the image or at least the one that is displayed on your page? This is important since if that variation wasn’t optimized webpagetest will flag it as non-progressive even if the other variations are.

  2. Neeraj

    After Reading this post, i have purchased optimus. But there is no option to convert in Progressive JPEG.

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