Lossy image optimization plugins

Image optimization plugins – Optimize images for free in WordPress

Optimizing images on the web is a necessity. If not optimized, images tend to decrease the overall UX of your visitors/customers.

Luckily, compressing images is an easy task on WordPress platform.

There are image optimization plugins that can really make your life easier and your users happier.

This is my list of top 7 WordPress image optimizers.

What does it mean to optimize images for the web?

First, let’s define what optimizing images means. Here’s the quote from GTmetrix:

Optimizing images for the web means saving or compiling images in a web friendly format depending on what the image contains. Images hold data other than just the pixels we see on the screen. This data can add unnecessary size to the image which leads to longer load times as the user waits for the image to download. -> GTmetrix

In other words optimizing image means compressing and removing all the unnecessary data that comes within the image. This way file size of the image is reduced by as much as 80%. Then we can draw a conclusion that image optimization is using the smallest file size which is still visually acceptable.

What are the reasons to optimize images?

If images play a significant role on your site, optimizing them could be essential for the success of your business. Reasons for image optimization include:

  • Decreasing page loading time – page load time is a major factor in a site’s success. It is an important part of website’s user experience. A user that has to wait is likely to hit the back button on the website. Losing customers that way should be unacceptable.
  • Decreasing bandwidth used – not optimizing images wastes precious bandwidth that will end up costing you money, customers, or both.
  • Saving hardware storage.

Best free WP image optimization plugins

Below is my list of top 7 free WordPress image optimization plugins. All of these plugins have at least 20,000 active installations each and they are regularly updated and maintained. You can install and use any of these plugins for free, but they all have premium versions/plans so free options have certain limitations.

I tried them all and ranked them taking into consideration the following factors:

1. List of features in the free version
2. Compression performance in the free version
3. Limitations in the free version

#7. Optimus–WordPress Image Optimizer

Optimus plugin

Optimus is very easy to set up and configure, but at the same time that means it lacks in features other image optimizers on this list have. Optimus supports only lossless compression of PNG images and a slightly lossy compression of JPEG images. On top of that you are limited to images up to 100 KB in size in a free version of the plugin. I picked one image 1280×800 px that was 145 KB and couldn’t compress it within free version… Serious problem there.


List of features in the free version: 2/5

Compression performances in the free version: 1/5

Limitations in the free version: 2/5

#6. Kraken.io Image Optimizer

Kraken plugin

Kraken requires API key for activation, but it offers more features than Optimus. Unfortunately, there is also a huge limit in a free version. Not in file size, but in free quota that you get – only 100 MB of images to optimize. Despite the good compression result, this means that if you are looking for free image optimization plugin, Kraken is most likely not going to cut it.


List of features in the free version: 3/5

Compression performances in the free version: 4/5

Limitations in the free version: 2/5

#5. Imagify Image Optimizer

Imagify plugin

Next on the list is Imagify. This plugin requires registration to get the free API key as well, but free plan allows you to optimize much more images than Kraken does. You get 25MB per month for free. However, while I was testing the PNG compression, I got a warning: File size must be under 2.0 MB. Current file size is 2.2 MB. Big problem there!


List of features in the free version: 3/5

Compression performances in the free version: 3/5

Limitations in the free version: 3/5

#4. EWWW Image Optimizer

EWWW plugin

No API key needed to start using EWWW Image optimizer, but without it you are restricted to lossless image compression only. API key will cost you just 0.99$ and after that, you are billed 9$ on monthly basis, but only when you use 3000 credits (compressed images). I didn’t purchase the API key, but they promise around 80% compression, just like the other plugins do. If that is true, depending on your requirements, if you go for the paid version, it would likely be cheaper than Imagify or Kraken. This is the only reason I placed EWWW image optimizer higher on the list, despite a very limited offer in the free version.


List of features in the free version: 2/5

Compression performances in the free version: 1/5

Limitations in the free version: 2/5

#3. Smush Image Compression and Optimization

WP smush plugin

WP Smush is the most popular image optimizer out there with 1+ million active installations, however the free version has a huge downside and that is why it’s not first on my list.

WP Smush resultsWP Smush doesn’t optimize the original image in the free version of the plugin! That means all of the alternative image sizes that are created automatically by WordPress on upload can be compressed, but not the original version. The one that you actually upload.

If you are using original image versions on your pages, which is most often the case, then you miss out big time. Your pages won’t have optimized images at all! At least not on desktop devices.

I always upload images in the exact size I need for my articles, and most of the visitors to this website use desktop devices. By using free version of the Smush image optimizer plugin I would be serving unoptimized images to 90% of my readers!

As you can see from the image on the left, WP Smush skips FULL image size (original image) in the compression process of the free plugin version.



List of features in the free version: 3/5

Compression performances in the free version: 3/5

Limitations in the free version: 4/5

#2. Compress JPEG & PNG images

TinyPNG plugin

Compress JPEG & PNG images by TinyPNG is a simple but effective plugin that allows you to compress JPG and PNG images, just how it’ s name suggests.

However, it doesn’t offer any extra features outside of that. Additionally, it requires API to work that allows you to optimize up to 500 images per month for free. If that is enough for you, this plugin is a good choice.

Just be careful, this cap of 500 images include alternative image sizes as well. For example, my theme creates 9 alternative image sizes alongside original, if I choose to optimize them all, this basically means I can compress total of 10 unique images per month if I don’t exclude some (or all) of the alternative image sizes from compression.


List of features in the free version: 2/5

Compression performances in the free version: 5/5

Limitations in the free version: 4/5

#1. ShortPixel Image Optimizer

Shortpixel plugin
I absolutely love ShortPixel image optimizer and it is a clear winner among free image optimization WordPress plugins for me.

It gives you all of the features for free! And compression is great. You can even choose three levels of compression: lossy, lossless and glossy. Further more, you can optimize PDF files as well. You can even convert PNG images to JPEG or create WebP versions of the images, all for free.

There is only one limitation in the free plan: you get to compress 100 unique images per month. But that is still much more generous than what other plugins offer for free. It is actually much more than I need for this website. If you do need more, there are paid plans available, but they are very affordable, starting from only 5$ for 5000 images which should really be enough for 90% of the users.

In order to install ShortPixel you need to get the API key here first. The process is extremely easy, just enter your email and you get API key in your mailbox.


List of features in the free version: 5/5

Compression performances in the free version: 5/5

Limitations in the free version: 4/5


Shortpixel offers the most features for free, but it also performs well. I used the jpg image below and optimized it using top three image optimizer plugins from this list.

Coffe image optimized by ShortPixel

The image you see is optimized by ShorPixel plugin. This compressed version has the size of 88 KB while the original had 291 KB. Check out the table below to see how that compression compares to the WP Smush (see compressed image) and TinyPNG (see compressed image).

Features WP Smush ShortPixel TinyPng
Original image (291 KB) compressed to: 291 KB (uncompressed)
88 KB 94 KB
Compress original full-size images NO YES YES
Back up original image NO YES NO
Choose between lossy or lossless compression NO YES NO
Optimize PDF NO YES NO
Choose which image to optimize on upload YES (apart from original size) NO YES
Create WebP version of an image NO YES NO

So if you see Optimize images warning in GTmetrix report, install ShortPixel image optimizer. Your users will be grateful and convert better 🙂 See for yourself, enter your website URL in ShortPixel compression test to see the results!

This article has been originally written in 2016, but I updated it in 2018 with 4 more plugins.


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