Deep Dive: Comparing the Top 10 WordPress Image Optimization Plugins (2021)
NOTES
- This comparison is not complete, but I published it anyway is case anyone finds the info useful.
- Some plugins don't give the option to leave thumbnails alone, so they will calculate more space saved. adjust accordingly or delete thumbnails.
In this post we'll take a deep dive into the top ten image optimization plugins for WordPress. First we'll talk about what image optimization is, then what options are available, and finally what situations might call for the various approaches to optimization. We'll compare features, prices, and compression data. We spent over 10 hours researching the top plugins, documenting their features, testing their capabilities, and detailing the results. There's a lot of information here, so let's start with a table of contents.
Table of Contents
What is Image Optimization?
When a camera takes a photo, its goal is to capture as much detail as possible. Unfortunately, the more detail that is stored in the file, the larger the file size.
Most images contain details that aren't visible to the human eye. Image optimization plugins attempt to remove these hidden details to reduce the file sizes and speed up page load times.
There are two times of image compression: lossless, and lossy. Some plugins support lossless compression, some plugins support lossy compression, and some plugins support both.
Lossless Compression
Lossless compression finds ways to compress the file size of an image with no loss of actual image quality. The image's pixels remain the same. This is great for photography sites, or other sites that require extreme image quality. However, lossless compression is limited in how much it can reduce file sizes.
Lossy Compression
Lossy compression reduces the image quality along with the file size. Most images contain more details than the human eye can recognize, so lossy compression removes some of that extra detail to further reduce file sizes. Some plugins have settings to control how much detail can be removed during compression.
Images can be further optimized by using the correct file type. Photography and images that don't require transparency should usually be stored as JPEG files. Screenshots, illustrations, and images that require transparency are better stored as PNG files.
For further optimization, Google has released a new image format for the web called WebP. However, browser support for WebP is spotty. Implementing WebP can be difficult because some browsers must be served images in standard formats while other browsers can be served WebP files.
Many of the plugins listed here can export WebP files, and some can even handle serving those files to the proper browsers.
Why Image Optimization?
Image optimization plugins compress the file size of our images to allow them to load quicker. This has two primary advantages:
- It benefits our site visitors because it helps them find what they're looking for as quickly as possible and doesn't waste their bandwidth.
- Google uses page speed as a ranking factor, so having a properly optimized site can help your search rankings.
Common Features
There are some features that almost all image optimization plugins support. We won't be analyzing these features in our comparison, but it should be noted that they are supported by nearly all, if not all, of the plugins we'll mention.
Encrypted Transfer
Most of these plugins operate using the software-as-a-service (SAAS) model. This means that all our images get transferred to an external server for processing. Encrypting content during that transfer ensures that our images don't get tampered with along the way.
Progressive JPEG
Progressive JPEG files load at a low resolution and add clarity as they load. This allows them to load at the proper size, rather than starting at the top like traditional JPEGs. They look blurry and pixelated at first, but since they load at the proper size, other elements don't get pushed around during the loading process.
Batch Processing
Optimizing images one by one would be tedious. Automating this task using batch processing allows many images to be optimized at once.
Automatic Processing
As new images are added to the media library, they are automatically optimized as soon as they are uploaded.
Multiple Websites
These plugins allow us to use them on multiple sites.
Additional Features
In addition to the features that all the plugins share, there are a number of features that only a portion of the plugins support. These features are what will distinguish one plugin from another and what will help you determine what plugin is best suited for your website.
Custom image locations
The WordPress media gallery isn't the only place that images can be stored on the server. Custom image location support allows plugins to optimize images that are stored outside the media library folders.
CDN
Some plugins include a Content Deliver Network (CDN) to reduce the load on our servers by serving images more efficiently from specialized servers.
File size limits
Some services don't support large images. Any images over the file size limit will not be optimized.
Original image restoration
When an image is optimized, what happens to the original? That depends on the plugin. Some plugins keep the originals and even offer a quick way to restore your site to using all the original images.
Image resizing
In addition to optimizing image data, images with larger than needed dimensions can be resized to a more usable display size. This can significantly decrease the file size of especially large images.
EXIF options
EXIF stands for Exchangeable Image File Format, which is a method of storing additional data about an image within the image itself. Some plugins preserve this data, others remove it, and some give the user a choice of whether or not to preserve the EXIF data.
Account sharing/management
Account management allows the image optimization service to be used across multiple sites, with tools for tracking usage and setting limits on usage. If you are an agency or offer a site care service this can be beneficial.
Feature Comparison
This is where things start to get interesting. Below is a table of all the image optimization plugins we reviewed and all the distinguishing features we tracked.
| EWWW (Cloud) | Imagify | Kraken.io | OptiMole | Optimus | reSmush.it | ShortPixel | TinyPNG | WP Smush Pro | WP Compress | |
| SAAS | y | y | y | y | y | y | y | y | y | y |
| Self-hosted | y | |||||||||
| Lossless | y | y | y | y | y | y | y | |||
| Lossy | y | y | y | y | y | y | y | y | y | y |
| JPEG | y | y | y | y | y | y | y | y | ||
| PNG | y | y | y | y | y | y | y | |||
| GIF | y | y | y | y | y | |||||
| SVG | y | |||||||||
| y | y | |||||||||
| WebP export | y | y | y | y | y | |||||
| Image resizing | y | y | y | y | y | |||||
| Keep EXIF | y | y | y | y | y | |||||
| Remove EXIF | y | y | y | y | y | y | ||||
| Shared/managed accounts | y | y | y | |||||||
| Unlimited file size | y | y | y | y | ||||||
| Restore original images | y | y | y | y | y | y |
Image Optimization Plugins
Pricing Comparison
There are two different methods that image optimization companies use to calculate their rates. About half calculate their rates based on the file sizes of the optimized images, while the other half calculate their rates based on the number of images optimized regardless of size.
The two tables below display the cost of each services depending on the usage statistics.
There are a few companies that charge a flat monthly fee regardless of the number of size of images optimized. I've added those services to both tables for comparison.
Bandwidth/Month
| Plugin | 1GB | 2GB | 5GB | 10GB | 15GB | 20GB | 25GB | 50GB | 100GB |
| OptiMole | Free | 9.00 | 9.00 | 9.00 | 29.00 | 29.00 | 29.00 | 29.00 | Custom |
| Imagify | 4.99 | 8.99 | 19.99 | 34.99 | 39.99 | 49.99 | 59.99 | 69.99 | 119.99 |
| Kraken.io | 9.00 | 9.00 | 19.00 | 34.00 | 39.00 | 49.00 | 59.00 | 79.00 | 119.00 |
| Optimus | 12.42 | 12.42 | 12.42 | 12.42 | 12.42 | 12.42 | 12.42 | 12.42 | 12.42 |
| reSmush.it | Free | Free | Free | Free | Free | Free | Free | Free | Free |
| WP Smush Pro | 49.00 | 49.00 | 49.00 | 49.00 | 49.00 | 49.00 | 49.00 | 49.00 | 49.00 |
Images/Month
| Plugin | 50 | 100 | 500 | 1,000 | 5,000 | 10,000 | 25,000 | 50,000 |
| TinyPNG | Free | Free | Free | 4.50 | 40.50 | 85.50 | 115.50 | 165.50 |
| ShortPixel | Free | Free | 4.99 | 4.99 | 4.99 | 9.99 | 29.99 | 29.99 |
| EWWW (Cloud) | 0.99 | 0.99 | 1.50 | 3.00 | 15.00 | 30.00 | 75.00 | 150.00 |
| Optimus | 12.42 | 12.42 | 12.42 | 12.42 | 12.42 | 12.42 | 12.42 | 12.42 |
| reSmush.it | Free | Free | Free | Free | Free | Free | Free | Free |
| WP Smush Pro | 49.00 | 49.00 | 49.00 | 49.00 | 49.00 | 49.00 | 49.00 | 49.00 |
| WP Compress | 2.42* | 2.42* | 2.42* | 2.42* | 8.25* | 8.25* | 20.75* | 41.58* |
* WP Compress optimizes thumbnail images and all additional image sizes added by themes and plugins for free.
Optimization Comparison Setup
In order properly compare optimization between plugins, we need a standard set of tests to run on each plugin. We downloaded 2 images from Unsplash and took 2 images with a 20.2 megapixel digital camera. From each source, we used one image with great detail and one image with much less detail. Here are the images:
Unsplash #1 (3.6mb)
Unsplash #2 (1.9mb)
Camera #1 (6.5mb)
Camera #2 (4.0mb)
We then spun up a staging site and installed all the image optimization plugins, uploaded the images, and created a site backup so we could reset our site after testing each plugin.
Optimization Comparison Results
...
Lossless
| Plugin | Unsplash #1 |
Unsplash #2 |
Camera #1 |
Camera #2 | Total |
| EWWW (Cloud) | |||||
| Imagify | Skipped | 1.6mb/16% | Skipped | Skipped | 16% |
| Kraken.io | 9.00 | 9.00 | 19.00 | 34.00 | 39.00 |
| Optimus | 12.42 | 12.42 | 12.42 | 12.42 | 12.42 |
| reSmush.it | Free | Free | Free | Free | Free |
| WP Smush Pro | 49.00 | 49.00 | 49.00 | 49.00 | 49.00 |
| OptiMole | Free | 9.00 | 9.00 | 9.00 | 29.00 |
Lossy
| Plugin | Unsplash #1 |
Unsplash #2 |
Camera #1 |
Camera #2 | Total |
| EWWW (Cloud) | |||||
| Imagify | Skipped | 0.81mb/57% | Skipped | Skipped | 0.81mb/57% |
| reSmush.it | 6% | 15% | 66% | 3mb/31% | |
| Kraken.io | 9.00 | 9.00 | 19.00 | 34.00 | 39.00 |
| Optimus | 12.42 | 12.42 | 12.42 | 12.42 | 12.42 |
| reSmush.it | Free | Free | Free | Free | Free |
| WP Smush Pro | 49.00 | 49.00 | 49.00 | 49.00 | 49.00 |
| OptiMole | Free | 9.00 | 9.00 | 9.00 | 29.00 |
* Please note: not all data in the following table is created equal. Each plugin has it's own settings for lossy compression. These settings cannot be accurately replicated across plugins in our tests, so we accepted the default or recommended setting for each plugin.
| Plugin | 50 | 100 | 500 | 1,000 | 5,000 | 10,000 | 25,000 | 50,000 |
| TinyPNG | Free | Free | Free | 4.50 | 40.50 | 85.50 | 115.50 | 165.50 |
| ShortPixel | Free | Free | 4.99 | 4.99 | 4.99 | 9.99 | 29.99 | 29.99 |
| EWWW (Cloud) | 0.99 | 0.99 | 1.50 | 3.00 | 15.00 | 30.00 | 75.00 | 150.00 |
| Optimus | 12.42 | 12.42 | 12.42 | 12.42 | 12.42 | 12.42 | 12.42 | 12.42 |
| reSmush.it | Free | Free | Free | Free | Free | Free | Free | Free |
| WP Smush Pro | 49.00 | 49.00 | 49.00 | 49.00 | 49.00 | 49.00 | 49.00 | 49.00 |
| WP Compress | 2.42* | 2.42* | 2.42* | 2.42* | 8.25* | 8.25* | 20.75* | 41.58* |
* WP Compress optimizes thumbnail images and all additional image sizes added by themes and plugins for free.
Plugin Strengths and Weaknesses
Here we want to cover some of the strengths and weaknesses we found in our research and testing. This will hopefully be helpful in determining whether or not a particular plugin is right for your project.
EWWW
reSmush.it
Pros
- Payment is optional and donation based.
Cons
- Individual file size limit of 5mb.
- Some of the text on the settings page is extremely small.
Imagify
Pros
- Incredibly simple to use
- Multiple levels of lossy compression
- Allows compression of specific folders
Cons
- Displays ads and notifications for other plugins by the same company.
- Free version has an individual file size limit of 2mb.
Our Recommendations
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