An image CDN (Content Delivery Network) can significantly improve your website’s performance by reducing images’ file sizes by up to 80% and delivering them in next-generation file formats, like WebP and Avif, from the edge of the network. Smaller file sizes mean faster page load times, reduced bounce rates, improved search engine rankings, and increased revenue.
Unfortunately, the web is awash with misinformation about image CDNs, largely due to competing companies hawking their services.
This post is an unbiased, up-to-date review of the leading image CDNs in 2023. We’ll start by explaining what an image CDN is and how it can benefit your business. Next, we’ll cover the essential features to look for in a good image CDN. Finally, we’ll finish with recommendations for the best image CDN for every type of business.
After reading this guide, you will have the necessary information to make a well-informed decision regarding an image CDN and a list of recommended services to consider.
What is a CDN?
What many people don’t realise is that the internet is a physical thing. When your browser loads an image, the data that makes up that image is stored on a physical server and sent to you down physical wires.
As with any physical thing, the further away website data is, the longer it takes to reach you.
When you access a website hosted on a server near you, the network will deliver the data quickly. However, if the server is located on another continent, the data will have to travel long distances through oceans, mountains, and plains, all while competing for priority with other data.
A CDN addresses this issue by replicating your website and hosting the copies on various servers globally; the distance your data needs to travel is reduced, and as a result, your site is faster for the end-user.
This way, regardless of the location of your users, the distance the data has to travel is minimised, bottlenecks are reduced, and your website is faster.
3 Main Benefits of an Image CDN
CDNs can benefit all types of data, but they offer the most benefit to large data files like images.
For most websites, images are the single largest file type; images make up around 55% of the total webpage size, even on a heavily optimised website. Reducing the size of images by automatically converting them to next-generation formats like WebP is the low-hanging fruit of website optimisation.
Benefit 1: Improved Search Engine Ranking
By reducing the size of your images, you improve multiple ranking signals that search engines (notably Google) use to rank web pages.
For instance, Google believes that users prefer websites that load quickly [spoiler alert: we do] and has introduced Core Web Vitals to guide web development towards faster and more satisfying user experiences. One aspect of Core Web Vitals is the First Contentful Paint metric, which measures the time taken for the first piece of content to be visible on the screen; for many designs, this means an image.
When it comes to search engine optimisation (SEO), faster is always better.
Benefit 2: More Responsive Bitmap Images
In modern web design, there is an approach referred to as ‘responsive web design’ or ‘RWD’ — the practice is so ubiquitous that it is widely regarded as synonymous with web design.
In RWD, websites respond to the device on which they are accessed — principally, but not exclusively, taking their cue from viewport size — meaning that design elements such as layout will change depending on whether a website is accessed on a mobile device or a laptop.
While text, layout, colours, and even vector-based images can adapt dynamically using CSS (cascading style sheets); bitmap images that are made up of pixels (such as photographs) cannot.
It is technically possible to resize bitmap images with CSS, but doing so doesn’t actually reduce the number of bytes delivered to the browser. Image CDNs can scale down bitmaps before the browser receives them, meaning that the user downloads the smallest file possible while still seeing the same high-quality visual.
Benefit 3: Practical Image Management
When we design websites, we typically reuse images in multiple locations. For example, a single image might be used as a product shot, as a thumbnail image in several different places, and enlarged on the home page.
Manually creating and maintaining multiple variations of an image is time-consuming and requires a designer or art director to anticipate every possible use case for an image.
Image CDNs solve this problem with the same mechanism they use for responsive image delivery, by dynamically serving an optimised version of the image in the correct ratio and size for each use.
How an Image CDN Works
When you think about an image CDN, it helps to think in terms of a source image and a distributed image.
The source image is the image you produce and upload to your CDN; it is stored on the server in its original state. The distributed image is the image that will be sent to any browsers that request it; it will be optimised and transformed. There can be many distributed images from a single source image.
When a user accesses your webpage by entering the URL in their browser, the request for images is routed to your CDN. First, the CDN checks if it already has a copy of the requested image stored in its cache. If not, it requests a copy from a processing server. The processing server retrieves the source image from the storage server and applies any necessary manipulation and optimisation. The newly created image is then sent to the user, and a copy is stored in the CDN’s cache in anticipation of future requests. The entire process occurs in a matter of milliseconds.
Apart from the speed, the real benefit of this approach is that it’s non-destructive; the source image itself is never altered, so you can change your design without having to recreate all of your images.
Typically an image CDN will either accept requests via an API, or via a query string. In the latter case the URL for accessing a CDN can be broken down into four parts:
- Origin server: the image is hosted on the origin server. It might be a white-labelled CDN using something like cdn.webzagger.com, or, as is the case with budget solutions, it may be the CDN’s domain.
- Source image: if an image CDN includes a media library, you might refer to the image path on the server, alternately you may host the image yourself and pass the full URL to the CDN; either way, you’ll need to tell the CDN which image to use.
- Security key: a security key is often required, in which case your CDN will generate it for you. (A good image CDN will also have additional security measures, such as asking you to list the domains permitted to transform your images.)
- Transforms: The final part of the URL typically specifies the transforms you wish to apply to the source image. Transforms can be anything from size, and pixel density, to compression format.
How to Choose an Image CDN
A specialist image CDN will speed up your website and provide a range of image-specific functions.
The ability to serve modern image formats, resize images without visible loss of quality, and detect the end-user’s device capabilities are essential. Beyond that starting point, here’s what to look for in a good image CDN:
A good image CDN has reasonable defaults, allowing you to plug your site into the service without extensive configuration.
We would go so far as to say that you should not change the defaults because, as technology adapts, the CDN will adapt for you. For example, prior to version 16, Safari did not support Avif files; when Safari 16 was released in October 2022, image CDNs began serving Avif files to Safari 16 users by default, without site managers needing to change their configuration.
Responsive web design isn’t just about adapting a design to the dimensions of a user’s browser but also adapting to the user’s environment.
A top-of-the-range iPhone has a high resolution and is very fast when connected to 5G. But the same iPhone will display slow speeds when the connection is patchy. A good image CDN will adapt the images it delivers not just by device capabilities but also by the capabilities of the end user’s connection.
Smart Image Manipulation
When manipulating images dynamically, it’s easy to crop essential parts of an image accidentally, especially if the subject isn’t right in the centre of the picture.
Good image CDNs feature smart image cropping to avoid cropping the wrong parts of an image. Great image CDNs use AI (Artificial Intelligence) to detect the regions of an image that they can safely cut.
No Perceptible Loss of Quality
The only way to reduce the file size of an image is to remove data — this is known as lossy compression. The trick is to only remove redundant data. A good image CDN uses AI to ensure that discarded data does not lead to a noticeable reduction in image quality.
Image CDNs tend to be built on the infrastructure of existing CDNs.
Just as sending website data over significant distances slows down the data transfer, processing servers for CDNs situated a long way from customers slows down the CDN’s operation.
A widely distributed CDN is essential for underpinning a good image CDN service.
Not all image CDNs are made equally. Some will reformat images into next-generation formats; others will simply crunch your image down to the requested size while retaining the original file format.
However, some image CDNs offer more image manipulation than is worthwhile. For example, very few websites need to use watermarking — it’s an outdated practice. There’s no need to pay extra for premium features if all you really need is good compression and fast delivery.
The Best Image CDNs for 2023
We’ve looked at all of the available options for compressing and distributing website images, and here are our preferred solutions right now.
ImageKit is one of the most popular image CDNs available. It is robust and straightforward to implement.
Choose ImageKit if you’re looking for a great all-rounder that suits most organisations.
- Intelligent smart-cropping and face-detection for automated thumbnail generation;
- 40+ optional image transforms;
- support for video formats;
- integrated asset management;
- powered by AWS.
There’s a free-forever plan with a very generous resource allocation, including 20Gb of media storage and unlimited transforms.
The free-forever plan is more than enough for testing, and smaller sites might never need to upgrade to a paid plan.
Beyond the free-forever plan, the premium plan starts at $49/mo. As well as doubling your bandwidth, the premium plan includes white-labeling for your domain and a 30-minute consultation with an optimisation expert.
Enterprise pricing starts at $500/month.
Resizely is the bare bones of an image CDN. Instead of competing on features, Resizely offers a stripped-down, fast and straightforward solution.
Choose Resizely if you want a pure, simple-to-implement image CDN, with few additional features to get in the way.
- Speedy server response times;
- simple, URL-based asset retrieval;
Resizely offers a free-forever plan for up to 1,000 unique images. It’s suitable as a trial and for small sites, but under the free plan, any requests above the allocation will be denied (as opposed to charged).
Resizely is one of the best-value options you’ll find for professional image CDNs.
Beyond the free trial, paid plans range from €9/mo for up to 10,000 unique images on the Starter plan to €45/mo for up to 100,000 unique images on the Pro plan. (Be aware that requests above the allocation are charged at €0.002 on the Starter plan and €0.001 on the Pro plan.)
Resizely also offers an Enterprise plan for up to 1,000,000 images, which costs €225/mo.
Cloudimage is an image CDN that provides a comprehensive set of features. It is geared towards key industries, such as real estate and ecommerce.
Choose Cloudimage if you have a large ecommerce site, if you’re managing thousands of images, or if the wealth of features appeals.
- Up to 75% reduction in image weight;
- real-user monitoring to benchmark global performance;
- static content acceleration means you can serve files like PDFs and CSS over the CDN;
- one-click integrations with WordPress, Magento, and Shopify.
Cloudimage offers a free-forever plan that can be used as a trial or for a smaller website. It includes 25 GB of monthly traffic, but be aware that you will be charged $1/Gb for overuse.
Plans range from $29/mo for the Startup plan, to $249/mo for the Rocket plan. Cloudimage’s top tier is comparable to other providers’ enterprise plans and, as such, is a good choice if you’re expecting to scale rapidly.
As well as the high-capacity Pro and Rocket plans, Cloudimage offers enterprise plans; contact them for custom pricing.
Also Worth a Look
We think ImageKit, Resizely, and Cloudimage are the best image CDNs for most projects in 2023. However, if you have niche requirements, there are other image CDNs available that are worth considering.
KeyCDN is a great image CDN for developers. It has an elegant API and is relatively easily integrated into most sites. It features detailed reports, so you know precisely how your content is being delivered. The downside with KeyCDN is that its pricing is somewhat opaque and varies by region. For example, the first 10Tb/mo in Europe is priced at $0.04/Gb, and the same volume in Africa is priced at $0.10/Gb. If you’re migrating a site and you know your usage precisely, then KeyCDN may be a good option. If you’re building a new website, make sure you carry out a detailed audit so you know what your costs are likely to be.
Cloudinary is a particularly robust image CDN for large ecommerce sites. If you’re running a store with Magento, then Cloudinary is a good choice. Most of Cloudinary’s power comes from its API approach; you’ll need coding skills or a development team to make the most of it. There’s a free-forever plan, and paid plans range from $89/mo–$224/mo. As you’d expect from a service pitched at medium-large sites, enterprise plans are available upon request.
Thumbor is a fantastic image CDN for image cropping and resizing. It offers far fewer features than most CDNs because it is open source, making it free to implement. However, unless you are an experienced developer, or have one on your team, the learning curve for implementing Thumbor is too steep to make it a viable option.
Cloudflare is much more than a CDN. It is a redirection service that sits between your domain name registrar and your web host. Its principal feature is protecting your site from DDoS attacks. If you’re using Cloudflare for site security, it makes sense to consider its CDN for your images, but it’s overly complex if all you need is an image CDN.
Fastly is one of the biggest names in image CDNs, winning multiple awards for its service, so you might expect it to make our main list, but it didn’t for one reason: Fastly expects you to anticipate your usage and calculate your own pricing. Businesses need the ability to make informed decisions, and Fastly’s plans are meaningless if you can’t attach a price tag for comparison. However, if money’s no object, or your monthly usage is stable and predictable, then Fastly could be the image CDN for you.
Imgix has been around since 2010, making it one of the most established image CDNs available. It offers a good range of features and is relatively easy to implement. There is a generous free-forever plan, and premium plans start at $75/mo. If you need a solution that’s like ImageKit, but with slightly higher tiers (and prices to match), then Imgix is a good alternative.
Which Image CDN Should You Choose in 2023?
For the majority of projects in 2023, we recommend ImageKit; it’s powerful enough to do everything you need an image CDN to do, relatively simple to implement, and good value.
Whichever service you choose, it’s vital that your images are served intelligently via a reliable CDN. When they are, you’ll find your site’s user experience and search engine rankings improve, which will, in turn, mean a greater return on your investment.