Comparing the Best Free Image Optimization Plugins for WordPress

Images make up the bulk of webpage content and as a website admin you should take steps to control the size and quality of images on your website. Optimizing your images is one important part of keeping your page load time down. You’ll surely want to keep an eye on image size in order to deliver your content in the fastest and most efficient manner possible. Doing so is good for SEO and user experience. Images can slow your site down, optimizing for the web is a must if you want to use high quality images.

The art of optimizing images takes a bit of experimentation. You want to find a balance between quality and file size. The best way to find out what works is to try a method and test it out with your own eyes. You will have to decide on things like what format you want to use as well as compression type.

There are lots of image compression plugins for WordPress. We are testing out 6 free WordPress plugins found at WordPress.org. The purpose is to see how useful these free plugins are for users who want to optimize images on their site.

Bulk optimization seems to be the preferred service these plugins provide, so you can take all of the images in your library and optimize them at once. I am interested in the weight difference for single images. Currently I optimize images in Photoshop and I am looking for an easier way to do so.

I want to see how well these plugins perform to compress images that are at least a few MB in size. So I can simply add them to my library without having to do much to them.

The Test Conditions

I am testing these plugins on a live site running the Twenty Sixteen Theme. We have two images, a JPEG and a PNG. The JPEG is 3.76MB and the PNG is 8.19MB. This might be a bit too much to expect from a free plugin but we will see what happens. This is a play by play walkthrough of my experiences with each plugin, so I will describe everything as it is happening. The criteria I am using to compare these plugins are

• Ease of use out of 5
• File size
• Limit on file size
• Limit on images
• Features out of 5
• Overall score out of 5

We are only testing two files, but we will also consider the bulk image compression results for the smaller images. By default every image in WordPress has a few sizes. When you upload an image it is automatically copied and resized by WordPress to be used for thumbnails, medium size and large size. Some themes or plugins will add more sizes.

Most of the time, a WordPress image compression plugin will be able to optimize each image you upload 5 times, for the thumbnail, medium, medium-large, large the orginal. To see the default size settings for images added to the media library, go to Settings > Media.

A Primer on Image Compression

We aren’t going to get too academic here by any means. For our purposes we are looking to add images and make sure they look good on devices that they will appear on. This means we want good quality with less expense (size). This is easy to easy to achieve with a plugin.

Currently web has 3 image formats that are supported by all browsers: GIF, PNG, JPEG. There are other formats supported but we won’t be dealing with them at the moment. There are two types of ways to compress images, lossy and losseless.

1. Lossy – removes some of the original image data
2. Losseless – preserves all the original image data

Lossless compression results in larger files than lossy. Most of the time, losseless is better for images that need to be printed on media like paper. For many images on the web today, it’s okay if you remove some of the data, because you won’t see any noticeable difference in quality.

Compression gets a lot more complicated than simply lossy vs losseless though. Both lossless and lossy algorithms are used to compress images into a format such as JPEG. Experts on the subject can wax and wane on the finer points of compression endlessly. Checkout this Google Developers information on Image Optimization.

Here all you need to know is that lossy can result in a much smaller file size, but it may affect the quality in a way that you don’t want. Sometimes complex gradients like skylines can undergo too much lossy compression and look bad on a device, that’s why I am using an image with lots of sky in it to test. Remember, let your eyes be the judge and don’t be afraid to sacrifice a bit of quality for a smaller file size.

Imagify Image Optimizer

Imagify seems to be a popular hit among WordPress users, there are lots of good reviews and not any bad ones I can see. They need your email address for you to try the free version. Once you install it you can easily get an API key as long as you enter a valid email. I really like the settings panel on this plugin. If you are visually inclined you will appreciate the colorful buttons, checkboxes and layout. So far this one is the smoothest and easiest to use.

Now let’s see how it performs. After install you will see Imagify under Settings > Imagify. New options will appear in the media library as well. Imagify offers bulk image processing as well as the option to optimize a single image. This is a true test drive, offering you 25MB of image optimization per month.

The features offered are very impressive as well with things like restore original and three different levels of compression: normal, aggressive and ultra. After I compressed the JPEG I was very impressed with the results. The file sizes was much smaller and the quality was still very nice. I couldn’t test the PNG because there is a 5MB limit on file size.

• JPEG before: 3.76MB
• JPEG after: 1.29KB
• PN: before: 8.19MB
• PNG after: n/a
• Ease of Use: 5
• Features: 5
• Image Limit: 25MB per month
• File Size Limit: 5MB
• Overall Score: 4

WP Smush — Image Optimization

WP Smush is what we use here on this blog. It works I suppose but I never really thought too much about it. I use Photoshop to compress my images before I upload them, so they are already optimized by the time I upload them. I’m not sure how useful the free version is at all for me.

This plugin is very simple. Install it, activate it and set it up. The free version has 3 settings. You can set it to “automatically smush” your images, preserver EXIF data and resize images upon upload. If you set these to auto, your images will automatically be optimized when you upload them. I’m not really happy with the 1mb limit, I don’t see any use for the free version on my end. But it can be great for bulk optimization.

The pro version comes with some more features like bulk optimization (up to 50 images), no 1mb limit and resizing. I could see the pro version working because I could automatically resize and save more space. Plus there is no 1mb limit. You can try it free for 14 days. I might do that with another project but not today. For someone who needs to deal with a lot of images, I think the pro version is worth checking out.

During my test run it did further compress the default image size for and saved lots of space. It’s unfortunate that the free version has such a small limit, but trying it out can show you just what the pro version can do. It may be a little unfair to be harsh because of the limit, so we will revisit this in a future post on premium image plugins. I do like that this plugin gives you the option to automatically optimize images you upload or you can do each one manually. Another plus is the interface, it’s well thought out and my second favorite of all the plugins on this list.

So the free version does compress smaller sized images which can help if you have a lot on your site, but as far as a free solution to compressing larger files this one isn’t the best out of the bunch.

• JPEG before: 3.76mb
• JPEG after: n/a
• PNG before: 8.19MB
• PNG after: n/a
• Ease of Use out of 5 = 5
• Features = 3
• Limit: 50 images
• Filesize Limit: 1MB
• Overall Score: 3

Compress JPEG & PNG images

Compress JPEG & PNG images seems simple enough. You get 500 free photos per month to optimize. That equals 100 if you want to optimize the thumbnails, medium, large and post thumbnail versions of your image as well.

Just like with WP Smush, it’s not exactly free, but moreso. You need an API key, which requires your name and email address. I will bite this time. So I enter my name and email address in and get an API key. Nice, I’m in.

This plugin works through the native settings panel in the dashboard. Go to the Settings>Media section and you will see new options after install. I don’t see any way to compress a single image, only a compress all images button. I only have two on my tester site so I don’t mind. The images compressed and it saved quite a bit of memory.

This plugin works great if you have limited images to work with 100-500 per month. It’s quite useful and there are no limitations on the size you’d like to compress. I like this a lot, the only I wish they added was a way to compress images one by one. Otherwise everything went well with this plugin.

• JPEG before: 3.76MB
• JPEG after: 273KB
• PNG before: 8.19MB
• PNG after: 2MB
• Ease of use: 5
• Features: 4
• Image Limit: 500 per month
• Filesize Limit: none
• Overall Score: 4

ShortPixel Image Optimizer

So this one gives you 100 free images to optimize every month. If you need more you can pay as you go. For $5 you can get credits for 5,000 images. There is no file size limit, which I like. Apparently, the only difference between the paid version and the free one is the amount of images you can compress, otherwise all the same features are available. Nice.

To try the free version you will need an API key for this one, which requires your name and email. So it’s not completely free but I’m not complaining. Anyone who builds a useful open source tool is usually someone I don’t mind sending me emails. After you install it you will can go the plugin settings from the dashboard via Settings>ShortPixel.

So once I entered the API key the settings panel appeared. There are plenty of options which include compression method, resizing and image backups. There’s also tabs in the settings panel to look at stats and find resources.

To see how it performs, I will optimize my images one by one. Once ShortPixel is active, you can compress single images from the media library’s list view. It will optimize the image and the 5 thumbnails using the lossy compression setting. After less than a minute on each image it worked. This plugin was a success and I am happy with the quality of the images.

• JPEG before: 3.76MB
• JPEG after: 267 KB
• PNG before: 8.19
• PNG after: 2.28MB
• Ease of Use: 5
• Features: 5
• Image Limit: 100 images
• Filesize Limit: none
• Overall Score: 5

EWWW Image Optimizer

Time to try EWWW. I read some of the feedback and it looks like people are having compatibility issues, but the majority of the feedback is good. The name stands out, let’s see how it performs. This one seems to have a lot of features and settings.

We are only testing JPG and PNG files, but this one has options for PDF and GIF as well. If you know a little bit about compression, this one gives you more choices. Many people may find that useful. After you install it you can find the options panel under Settings>EWWW Image Optimizer in the dashboard. There are also 2 new items under the Media section of the menu, Bulk Optimize and Unoptimized Images. Lets try it out.

I’m a little confused as how to optimize. At the top of the settings panel I see a link for “bulk optimization.” I guess I will try that option. It is supposed to skip the images that are already optimized. It shows I have 2 images that haven’t been compressed. I will go ahead and click the “Start Optimizing” button. It says it finished. But when I go to my library, nothing has changed. The files are still the same size. That’s strange. Absolutely nothing seemed to happen, not even with the smaller image sizes.

Now when I go back to the settings panel it says there are 0 unoptimized images. I will give it another go and choose “force it to reoptimize” and try to do a bulk optimization. Still nothing happened. That was disappointing. I hate to put a negative review since the problem may just be a bug or something on my end. But this plugin didn’t work at all for me. Even if it did work, it’s not the most user friendly one on this list.

• JPEG before: 3.76mb
• JPEG after: n/a
• PNG before: 8.19
• PNG after: n/a
• Ease of use: 3
• Features: 4
• Image Limit: none
• File Size Limit: none
• Overall Score: 1

Optimus — WordPress Image Optimizer

Right away I can see that I am going to have a problem. There is a 100kb limit. This is tiny. The only images I can compress will be smaller thumbnails, which are already compressed due to resizing. The difference in weight is going to be negligible in this case.

Once again though, if you have lots of images this could still give you some savings on bulk optimization. So this one is basically free to try and if you like it you can upgrade to the pro version. The problem with this is that I personally have no reason to optimize the thumbnails and other sizes. I can see someone with tons of images finding this useful though.

For the purpose of this post we are trying to see the weight difference on two images that are both way above 100kb. This plugin can optimize via lossy or lossless, but only with the pro version. So the free version really didn’t top this list because of the limit, but the bulk optimization can be useful.

• JPEG before: 3.76MB
• JPEG after: n/a
• PNG before: 8.19
• PNG after: n/a
• Ease of use: 4
• Features: 3
• Image Limit: none
• File Size Limit: 100KB
• Overall Score: 3

Final Words

Although some of the plugins on this list weren’t able to compress the original image, most of them are still worth the price, free. Perhaps expecting a free plugin to optimize larger file sizes is unrealistic. After all, you do get what you pay for and the pro versions may work out much better.

Everyone of them worked to compress the smaller images and save dozens of kilobytes except for EWWW, which didn’t work at all. If you have some images and you want to compress the smaller sizes, they will all do the trick. My favorites out of the group were Imagify Image Optimizer, Short Pixel Image Optimizer and Compress JPEG & PNG Images. WP Smush is still a great free plugin even with the 1MB limit, I gave it a 3 compared to the other free plugins — which have less limitations. I’d like to try the pro version soon to see what it’s like.

I think as far as a free plugin to automate image compression, I still think I will use Photoshop until I decide to get a pro version for an upcoming project. Mostly because I do things like resizing and free transform. These all work very well for compressing the smaller images, which saves you lots of space if you have hundreds to work with.

But even if you have a limit of 500 images per month, you’ll only save something like 15MB overall if you compress 500 images. That’s not alot but it is something. Test driving these was fun and I’m glad I got to. Do you have any favorite image compression plugins? Let us know your favorites and how they affected your site’s performance.