Here at Barrel Roll, we have members in a wide array of industries but one thing they all have in common is the need to have their websites perform at peak levels. When we do our initial assessments we nearly always find that there is image optimization to be done and that led us to look for the absolute best WordPress image optimization plugin.
We chose six of the top rated and most downloaded plugins and put them through a rigorous test meant to simulate scenarios we typically see with our members but under controlled conditions. Full details of how we tested can be found below under Methodology, but to put it simply, we created brand new WordPress installations on the same server for each plugin and optimized nine stock images at a maximum of 1,920px wide and the same nine at 1,200px for a total of 18 images. Then we compiled the results and found some clear winners and losers with a few surprises along the way.
Smush has been around a long time and has earned a reputation for being a reliable tool to optimize images. With over 700,000 active installs, they must be doing something right.
However we couldn’t get very far with Smush. They impose a 1MB file size limit with the free version of their plugin which is the most restrictive of all the plugins we tested and meant that only 5/18 of our images were processed. The results of the optimization of those images were exactly the same as EWWW in lossless mode, so we think it’s safe to assume they are using the same Jpegtran software to process images. That means you will see around 5% savings when using Smush in lossless mode. In order to see any significant gains you’ll need to pony up and join WPMU, but even then WPMU only promises up to 14.92% reductions using the Pro version and that’s using lossy compression.
So why is Smush so popular? It has the virtue of having been around a long time, since 2008, and has a big development team behind it which provides active support. Our experience was a bit rocky. We couldn’t get Smush to see the images in the Media Library unless we used the Media Library itself to upload the images and bulk Smush wouldn’t work until we disabled all of the image size variations, even though they weren’t on the server. The free account restricts you to processing 50 images at a time and all of the advanced settings require the Pro version. The 1MB file size limit combined with the 50 image restriction would make it difficult to recommend Smush and the comparatively low reductions that Smush Pro promises makes it hard to recommend paying for the Pro version, either.
A stalwart in WordPress image optimization, EWWW is the second most popular plugin with over 400,000 active installs. It’s easy to use; just install the plugin and go to Media>Bulk Optimize, scan your folders, and then optimize. There are no file size or number restrictions and unlike the other plugins here, EWWW processes images on your local server which usually results in faster processing (if your server can’t handle it, there is a cloud version).
EWWW defaults to lossless optimization so the overall reductions are lower but it seems logical to us to start with processing that doesn’t alter the images and give the user the choice to degrade the quality for a lower file size (even if that degradation is practically unnoticeable). Nearly all of the advanced options are available in the free version, including PNG and GIF optimization, resizing, scheduling, and parallel optimization for even faster performance.
File size savings were substantially less than the others that default to lossy compression, which is understandable. We already have an API key with credits (it’s really inexpensive) so we went ahead and did a separate test to give EWWW a fair shake. With the plugin set to maximum lossy we saw much better performance – an average of over 78.31% reductions – though not as good as ShortPixel. The API key also unlocks a few additional features, such as PDF compression. While the free version will shave around 5% off of your image sizes, you will probably want to purchase some credits in order to see better results.
Imagify has over 50,000 active installs and is made by WP Media, the folks who develop our favorite caching software, WP Rocket. After creating an account and obtaining an API key you must verify your account or some images may fail to optimize; a problem we ran into during testing. It would be great if there was some sort of notice about this before optimizing so time wouldn’t be wasted running optimization multiple times.
Like Smush, Imagify limits the size of the files that it will optimize with a free account but their limit is 2MB so we were able to compress most of our files. You’re limited to 25MB of image processing per month with a 25MB “bonus” for signing up, but that probably won’t get you very far, especially with variants included. It should be enough to give you an idea of what to expect from the plugin, and what we found was a well designed interface that gets the job done without being too cluttered or complex. You can choose between three levels of optimization: Normal (lossless), Aggressive (lossy), and Ultra (more lossy). Aggressive is default so that’s what we ran.
Since we couldn’t process all of our 1,920px images due to their 2MB file size limit, we can’t tell you the total savings. However, the 1,200px images came in at a size 62.47% smaller than the originals and the average of the five larger files it did process was a 53.42% reduction. We think it’s a safe bet that Imagify would be around a total savings of 60% all of the files been included, which puts it fourth in our list.
While the interface is well done and we’d expect support to be top-notch, it’s difficult to recommend Imagify when the performance isn’t there and it doesn’t have any other features that really separate it from the pack.
Kraken has been around for about three years as a WordPress plugin and has around 20,000 active installs. They have a great free web interface and have integrated the same technology with their WordPress plugin, which oddly requires account creation in order to use it at all. While this seems like an unnecessary step it’s handled fairly efficiently so you should be ready to go after a few minutes.
The interface for Kraken exists in its own page under Settings where you’ll find all the usual options, including the ability to choose lossy or lossless, resize images, and a few others that are more unique like automatic orientation which uses EXIF information that it strips by default (so we’re not sure how/if that works) and the ability to ignore the main image when optimizing which could be useful if you’ve already got it set the way you want but need the variations to be optimized.
What’s missing is a bulk optimization interface. While it’s possible to optimize images in bulk from the Media Library, you can process as many as you can populate on that page, which defaults to 20 (you can change this by clicking Screen Options and changing the “Number of Items Per Page” setting). Some servers will choke if you try to generate a page with hundreds or thousands of records returned and with so many other plugins providing well designed bulk optimization interfaces this seems like a major omission.
The performance of Kraken was lackluster. It was quick to process the images, taking only 26s, but the overall reduction in file size was just 54.12%, the lowest lossy figure in our roundup. It was the only plugin to score higher on optimizing lower resolution images than higher resolution, leading us to believe that it probably wouldn’t handle larger images very well. You’re also limited to just 100MB with the free account; it’s not clear if this is monthly or one-time. There are a lot of unanswered questions in the WordPress support forum and the plugin hasn’t been updated in over seven months. We can’t recommend it until we see more activity from the developers and better performance.
From the creators of TinyJPG and TinyPNG comes the almost painfully SEO friendly named Compress JPEG & PNG Images. The plugin has over 100,000 active installs and includes a strong core feature set. Like make plugins in our roundup, it requires account creation, activation, and an API key before you can begin using it.
The free version comes with 500 compressions per month, which works out to around 100 images when you consider that WordPress usually creates around five variants of each image uploaded. The interface it integrated into Settings>Media, which could be good or bad depending on your preference, but has a solid bulk optimization interface and options to do so within the Media Library itself.
The options available are more limited than some others we tested, but the core features of resizing, removing EXIF data, and lossy compression are there. As EWWW and Compress both use the TinyJPG/TinyPNG software to handle lossy compression it’s no surprise that the results are identical. We saw the same 78.31% savings with both plugins. Compress did run about a half a minute faster, however, taking 2.5m to complete the optimization compared to EWWW’s 3m. This could be a factor if you’re looking to optimize large numbers of images at once, which would of course require purchasing credits.
At a little over two years old and with 30,000 active installs, ShortPixel is a relative newcomer to the image optimization game. Age isn’t everything; ShortPixel has chops.
With all the features you’d expect, including image resizing, removing EXIF data, and options to disable optimizing variants and choices between lossy and lossless, ShortPixel isn’t short on features (sorry). After activating your account and adding your API key you’ll have access to 100 credits per month, which should net you about 20 images if you also optimize the default number of variants WordPress creates. That’s pretty low, but at least you will get an idea of what you’d be paying for should you choose to but some credits.
What you’d get would be the best optimization performance on the market, according to our tests. ShortPixel outperformed the competition on every image we threw at it, scoring almost 5% better overall. That may not sound like a huge margin, but it could translate into gigabytes of saved bandwidth per month if you have a popular or image heavy site.
One thing we wish ShortPixel would change is to disable the backup option by default. ShortPixel stores all of your original images to a backup folder before being optimized. Part of why people optimize images is to save storage space on servers, and creating copies of the originals would actually increase the disk space used by your images. It just doesn’t make sense to do this since you already have the original on the computer you uploaded it from. This option is easily disabled in the settings but it just seems like it shouldn’t be enabled by default.
Conclusions & Recommendations
All of the plugins we’ve tested will reduce the size of your Media Library, speed up your page load times, and save you bandwidth. ShortPixel was the clear winner in terms of file size reduction, but that came at a cost; images optimized by ShortPixel are visibly more distorted than any optimized by the other plugins. If that doesn’t matter to you and you don’t need to process many images per month or don’t mind paying a bit to process more, then ShortPixel is a solid solution.
Kraken isn’t there yet. We frankly find the web interface to be more polished than the plugin. It needs a standalone bulk optimization interface and performance needs to be improved. Imagify has a great interface but their free accounts are too limited in terms of file size allowances and the size savings can’t compete with EWWW, Compress, and ShortPixel. Smush’s popularity is a bit baffling given that it has such severe restrictions out of the box including limiting the file size and number of files you can process at once. The best optimization Smush can offer is 14.92% according to their own website, so we can’t see any reason to recommend it.
EWWW finds a happy medium between file size and quality loss that we think gives it an edge over ShortPixel, but only if you spend a few bucks on credits to enable the maximum lossy setting. This results in a file size reduction close to ShortPixel but with sharper images that are nearer to the originals. EWWW and Compress use the same TinyJPG software to optimize images so their results are identical but the EWWW plugin has more features than Compress and doesn’t require an account to try it. By processing images on your server, EWWW has the potential to save you time when you bulk optimize and each time you upload a new image. Most of EWWW’s features are fully functional in the free version, another plus, and it has a great history of development and support.
Unless you’re looking for maximum file size reduction without regard to lost image quality then we recommend EWWW Image Optimizer. Be sure to continue reading to learn more about our methodology and compare the samples for yourself. Check out our List of The Best WordPress Plugins for more recommendations!
We downloaded nine unique stock photos of various sizes and resized them to a maximum of 1,200px and 1,920px wide at 100% quality with Photoshop (we realize that reduces the quality a bit but the test is how well the plugins optimize typical files, not how well they optimize raw files). We setup clean installs of WordPress 4.7.3 for use with each plugin and uploaded the files to the Media Library, being sure to disable as many variants as possible beforehand and then deleted and additional variants created by WordPress so only the 18 original files were left in each installation. We installed the plugin and bulk optimized the files (when possible). Feeling nerdy? Check out the complete report here.
Total File Size Reduction
We used each plugin to optimize the same 18 JPG files; nine at a max of 1,200px wide and nine at 1,920px wide. These numbers compare the total size of all of the files combined before and after optimization. Higher percentage is better, obviously. Imagify and Smush as not included because their file size limits prohibited us from optimizing all of our test files.
- ShortPixel 83.09% 83.09%
- EWWW (Max Lossy) 78.31% 78.31%
- Compress JPEG & PNG Images 78.31% 78.31%
- Kraken 54.12% 54.12%
- EWWW (Lossless) 5.28% 5.28%
1,200px File Size Reduction
Here is how the plugins fared with the 1,200px image set. Smush is not included because their file size limits prohibited us from optimizing all of our test files.
- ShortPixel 81.07% 81.07%
- EWWW (Max Lossy) 74.75% 74.75%
- Compress JPEG & PNG Images 74.75% 74.75%
- Imagify 62.47% 62.47%
- Kraken 57.45% 57.45%
- EWWW (Lossless) 4.75% 4.75%
1,920px File Size Reduction
Here is how the plugins fared with the 1,920px image set. Imagify and Smush are not included because their file size limits prohibited us from optimizing all of our test files.
- ShortPixel 83.53% 83.53%
- EWWW (Max Lossy) 79.07% 79.07%
- Compress JPEG & PNG Images 79.07% 79.07%
- Kraken 53.40% 53.40%
- EWWW (Lossless) 5.40% 5.40%
The numbers show that ShortPixel reduces the file size more than another other plugin we tested, but at what cost to the image quality? Below you can see a comparison of each plugins output blown up so the quality loss can be seen easily. ShortPixel may do the best job of reducing the file size but the loss of quality is noticeably higher than EWWW and Compress. This is less critical when the image is viewed at its native resolution, as seen in the before and after graphic. You can download a ZIP of all the files here.