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Ultimate 2021 Image Optimization Comparison – Best Image Optimization Plugins For WordPress

Back in 2017, we made a pretty good comparison of image optimizer plugins and services for WordPress, and we found out that ShortPixel was overall the best. Our analysis required a thorough exploration of the world of image compression for WordPress, and we did exactly that. Besides ShortPixel, we looked at other well-known image optimization tools, such as Imagify, Smush and EWWW Image Optimizer. We know that developing and maintaining the best image optimization plugin to speed up WordPress is a complex undertaking, therefore we believe it’s time to check the scores again to find out, objectively, which are the best image optimization plugins for WordPress in 2021.

Nowadays there are many other products that use a different approach, like taking the images and storing them on a CDN, from where they will be optimized and served. That’s the case of ShortPixel Adaptive Images, Optimole, WP Compress, Flying Images, etc. In this review, we’ll only focus on local optimization, where the images are compresses on your own server.

We are going to compare ShortPixel Image Optimizer with Smush, EWWW, Imagify, TinyPNG, Robin and Optimus, the most popular image optimization plugins in the WordPress repository in 2021.

Features comparison

Online image compressor

Wouldn’t it be nice to be able to see how the optimized images look before going to your WordPress dashboard and installing the plugins? Only three of the contenders offer this option:

  1. ShortPixel: Online image compressor available
  2. Imagify: Online image compressor available
  3. TinyPNG: Online image compressor available

Unfortunately, there is no online service for the rest of the tools: Smush, EWWW Image Optimizer, Robin and Optimus.

Free plans: overview and limitations

 Free quotaLimitationsFile size limit
ShortPixel100 credits/monthNoneNone
SmushUnlimitedOnly lossless compression

No WebP

Only thumbnail compression

No backups

No 3rd party integrations
5 MB
EWWWUnlimitedNo backups

Only lossless compression
Imagify20 MB/monthNone2 MB
TinyPNG500 images/monthNoneNone
RobinUnlimitedSlower support

Slower compression

No WebP

No automatic compression

No 3rd party integrations
5 MB
OptimusUnlimitedNo WebP

No EXIF removal
100 KB

We can see that there are two groups of free plans: the plans that have a limited monthly quota (ShortPixel and TinyPNG) and the unlimited plans that have a strong limitation feature-wise.

Basic features

After seeing what the free plans offer, let’s take a look at the basic image optimization features, the minimum we think any image optimizer should have to speed up WordPress: lossy compression, backup/restore functions, bulk processing and PDF compression. We’ll also list all the image formats every plugin supports.

PRO means that the feature is only available if you purchase a plan (paid feature).


* EWWW’s backup function is only available for 30 days.

** TinyPNG allows Lossy but it’s the only compression method you can use. It’s not possible to use Lossless or another less aggressive method to optimize images.


It’s important the plugin is flexible enough to adapt to all types of WordPress installations and environments. Now we are going to check if the plugins are compatible with WordPress multisite, WPML (the most popular solution for multilanguage sites) and/or WP Offload Media (offloads your media to external servers), and if they are able to optimize custom folders outside the Media Library.

PRO means that the feature is only available if you purchase a plan (paid feature).

 MultisiteWPMLCustom foldersWP Offload Media

Advanced features

What if you want more from your image optimizer? Does it allow you to do the following?

  • WebP generation and delivery: Google is increasingly pushing its WebP image format, which is proven to be more efficient than JPG/PNG. So, it’s important for an image optimizer not only to generate WebP images, but also to deliver them to your users.
  • AVIF generation and delivery: We’ve already discussed in this article why AVIF is the next step in image optimization.
  • CMYK to RGB conversion: Images for the web only need the RGB format and converting them from CMYK to RGB makes them smaller.
  • PNG to JPG conversion: This can dramatically reduce the file size, especially if you have camera pictures that are saved in PNG format. 
  • Resize original images: Recommended for large photos, like the ones taken with your phone. Saved space can go up to 80% or more after resizing.
  • Exclusion rules: There are always some images that, for some reason, you’d like to keep unoptimized. Considering this, it’s important to have a section where you can exclude them.

PRO means that the feature is only available if you purchase a plan (paid feature).

 WebPAVIFCMYK to RGBPNG to JPGResize originalsExclusion rules

* Optimus creates WebP images on paid plans, but it doesn’t deliver them to your users, so you’ll have to use a different plugin for this.

Extra features

These are the special or unique features which give the particular “flavor” of each tested plugin.

  • ShortPixel
    • Can optimize unlisted thumbnails. Those are thumbnails that are not registered in the metadata but only created alongside the other thumbnails.
    • Free for non-profits!
    • Can optimize your images even if your site is behind HTTP AUTH authentication.
    • You can use it together with ShortPixel Adaptive Images to serve your images from a fast CDN, freeing up server resources. Not only that, the plugin will serve adaptive images, so the exact needed size will be served to your users, and not the huge original image.
  • Smush
    • Can detect and show incorrectly sized images to the site administrator. This way you can manually resize them to adapt to the image container.
    • Can export your settings so you can upload and apply them to your other sites in just a few clicks.
  • EWWW Image Optimizer
    • Can add the missing width and height attributes to all images.
    • Can do faster optimizations by optimizing in parallel all generated images from a single upload.
  • Imagify
    • Detects what theme you are using and easily offers you an option to optimize your theme images as well.
  • TinyPNG
    • Allows you to keep specific metadata and strips out the rest of the image metadata. For example, you can keep only the copyright information.
  • Robin
    • You can alter the optimization order. That’s useful if you want to optimize your Media Library from old to new.
    • You can choose a custom compression mode, from 1 to 100.
  • Optimus
    • Can optimize only the thumbnails and leave the original image untouched.

Optimization results

This second part of the review will focus on the actual optimization, because after all, a plugin can have a million features but still offer the worst results and not speed up WordPress. First, we’ll take a look at the numbers and see how much the plugins can compress the images and then we’ll show you the visual results.

If you are the kind of person who likes to check the details for themself, you can download the archive with the test images from here.

The PNG format is less popular than JPEG, being used mainly for screenshots and images containing text. That’s why we’ll test 3 JPG images (large, medium and small) and 1 PNG.


Since each of the plugins has different pricing and features, we need to set some parameters.

  • We’ll make use of the compression level that offers the smallest file size possible. ShortPixel calls it Lossy, but every plugin uses their own naming.
  • If the plugin offers it, we’ll strip out any metadata from the image. That’s usually the EXIF information.
  • No PNG to JPG conversion will be done.
  • The rest of settings will be left to default.

Image compression

 JPG-1 (2.6 MB)JPG-2 (389 KB)JPG-3 (5.8 KB)PNG-1 (127 KB)
ShortPixel162 KB
102 KB
1.7 KB
40.9 KB
Smush*450 KB
357 KB
2 KB
39.6 KB
205 KB
3.1 KB
40 KB
Imagify---167 KB
1.5 KB
48 KB
TinyPNG251 KB
205 KB
3.1 KB
40 KB
Robin>251 KB
158 KB
1.2 KB
42.8 KB
Optimus*------2.1 KB

We can draw a few conclusions from these results.

  • ShortPixel is hands down the best image optimizer for large/medium JPG images, which is basically what 90% of the websites use.
  • On the other hand, also for the vast majority of images (large/medium JPG), Smush is doing a very poor job.
  • Robin may be giving the best results for small images, followed closely by ShortPixel and Imagify.
  • Almost all image optimizers give similar results with PNG images. The only exception is Imagify, that scores slightly lower than the rest.
  • It’s interesting to see that both EWWW Image Optimizer (with its Premium Plus optimization method) and TinyPNG give the exact same results. This probably means that they use the same algorithms.

*We have used the trial periods of each service to make use of their best compression levels. Neither Imagify nor Optimus offer trial periods or refunds, therefore we couldn’t fully test their compression levels.

Picture quality

Below you can see the picture quality. These are the screenshots of the resulting images, and because the screenshots are JPG files themselves, these are compressed, so what you see might not be the actual result. Therefore, we recommend you download the .zip file with all the images to see the results for yourself.


As previously mentioned, we won’t see here Imagify or Optimus. Here are the 100% cropped samples:

EWWW Image Optimizer


The 2nd JPG couldn’t be optimized by Optimus because of their limitations. The 100% cropped images:

ewww jpg2
EWWW Image Optimizer
imagify jpg2
robin jpg2
smush jpg2
spio jpg2
tinypng jpg2


This is the only JPG image that was able to be optimized by all the optimizers. Here are the full images, uncropped:

JPG 3 ewww
EWWW Image Optimizer
JPG 3 imagify
JPG 3 optimus
JPG 3 robin
JPG 3 smush
JPG 3 tinypng


The PNG image was not optimized by Optimus, because it’s larger than 100 KB:

ewww png1
EWWW Image Optimizer
imagify png1
robin png1
smush png1
spio png1
tinypng png1


Free plans are usually enough for personal sites, but if you have an online shop, a popular blog or any other kind of website that makes use of images on a more consistent basis, that means you’ll need to frequently optimize images to speed up WordPress. This requires that you purchase a plan from one the providers, so you can take advantage of all the features.

Ideally, we would show you a nice and well designed table comparing all the plans, but unfortunately, every provider uses a different pricing method, so we’ll have to use a good old list.


ShortPixel has monthly and one-time plans, and each give you a quota with a certain amount of credits to optimize images. Each credit is used to optimize one image or thumbnail.

Monthly plans (2 months for free if paid yearly):

  • $4.99/month – 7,000 credits/month
  • $9.99/month – 16,000 credits/month
  • $29.99/month – 55,000 credits/month
  • $49.99/month – 100,000 credits/month
  • $99.99/month – 220,000 credits/month

One-time plans:

  • $9.99 – 10,000 credits
  • $19.99 – 30,000 credits
  • $29.99 – 50,000 credits
  • $59.99 – 100,000 credits
  • $99 – 170,000 credits
  • $249 – 500,000 credits

All of the plans can be used for image compression on unlimited websites.


Smush offers three plans to optimize images:

  • $6/month – 1 site
  • $14/month – 10 sites
  • $29/month – unlimited sites

All of the plans allow to optimize unlimited images, although their terms of service mention the following:

We reserve the right to suspend API access to users that use an unusual amount of API requests or resources that we feel may impact the services to other members.

There are also other limitations on the plans, like CDN bandwidth, but they are irrelevant for local compression, which is what this review is about.

EWWW Image Optimizer

EWWW has 3 monthly plans as well:

  • $7/month – 1 site
  • $15/month – 10 sites
  • $25/month – unlimited sites

Like Smush, each of them includes unlimited local image compression and again, like Smush, the “unlimited” part has to be read carefully. In EWWW’s case, there is a “soft limit” of 25,000 images, and their terms state the following:

Unlimited Compress API keys are expected to be used reasonably and normally in order to protect the quality of service offered to all users. If we detect unusual API usage, we’ll email you to resolve the situation. In extreme cases, we may be required to restrict API usage.

In addition, EWWW has also one-time plans, starting from $3 for 1,000 credits. Higher plans don’t give a discounted price, so we are talking about $0.003 per credit.


Imagify has only two plans to choose from, and like their free plan, they count the total size of images+thumbnails optimized, not the number of images themselves.

  • $4.99/month – 500 MB
  • $9.99/month – Unlimited

As with every “unlimited” usage, their terms of service state:

When we detect something out of the ordinary in your Imagify usage, we’ll contact you to discuss the situation and potential alternatives. In extreme cases, we may be required to limit the Service usage.


They probably have the simplest pricing plans. You pay for what you use in a monthly basis, and that’s like this:

  • $0.009 per image compression, up to 9,500 compressions
  • $0.002 per image compression, from 10,000 compressions


Robin only allows to pay yearly for image compression, instead of monthly, and like ShortPixel, each plan gives you a maximum amount of images+thumbnails to optimize.

  • $39/year – 5,000 images/month
  • $89/year – 12,000 images/month
  • $299/year – 55,000 images/month
  • $499/year – 120,000 images/month


In order to be able to optimize an image that is larger than 100 KB (most of them are, to be honest), you must purchase a plan, and this is what you get:

  • $29/year – Unlimited images, only for private projects
  • $149/year – Unlimited images, for projects for customers

While it seems like a good deal, it is worth noting that you cannot optimize an image that is larger than 10 MB. They also have a small warning on their homepage that says:

No abuse of the service.

They don’t explain what that means and there are no terms of service either, so it’s not very clear what other limitations you may find.


ShortPixel is the obvious winner, because of its clear and transparent pricing, its features and online image compressor, and most importantly, the actual results. If we had to pick a second solely based on the image compression results, it would be Imagify. Imagify has a good free plan like ShortPixel’s, allowing you to use all the features as you optimize images, with just limiting the amount of images. However, you should be aware of their lack of features and pricing model.

EWWW is also a good choice to speed up WordPress, and you can sense the passion of its creator. The main advantage of EWWW is also its biggest weakness: too many settings. Of course, this observation is highly subjective, but we believe that a tool to optimize images shouldn’t force users to make a lot of technical decisions.

At the other end of the scale, we find Smush and Optimus. They have no online image compressor, their free plans are quite useless, offering almost no compression or features, and the results in the paid plans are disappointing. It’s worth noting that neither of these services is the main product of their parent company, and thus it’s understandable that they don’t get a dedicated team to work on improving them.

As WordPress’ popularity is rising, many WordPress users are looking for the best image optimization plugin for their needs. We hope that this guide will help you make a decision.

Images used for this test

IMG-1: photo by Brooke Lark, downloaded from Unsplash, resized 10%
IMG-2: photo by Naikare, downloaded from Naikare’s website
IMG-3: photo by Aaron Burden, downloaded from Unsplash, resized 2%
PNG-1: screenshot taken by ourselves from the ShortPixel Bulk Optimization page on a WordPress site

The images IMG-1 and IMG-3 were previously resized, so we could test images having varied dimensions.


We read and compared all the plugins’ settings, menus and websites, but it’s possible that we missed something or we got something wrong. If this is the case, please let us know and we’ll be more than happy to correct any errors.

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