Complete Guide to Image Optimization for Better Website Performance
It doesn’t matter what type of website you have – images are critical for maintaining user engagement and improving website performance.
However, non-optimized images can eat up the site’s storage space and lower its loading speed – in, fact, roughly 39% of visitors will likely leave a website due to a slow image loading time. To improve your website’s overall performance and provide a better experience for site visitors, image optimization is key.
The goal of image optimization is to reduce the file size of an image without sacrificing its quality. Consequently, consuming fewer resources, loading faster, and positively affecting SEO.
In this guide, we’ll cover everything you need to know about image optimization, including tips on how to do it and tool recommendations.
What Is Image Optimization?
Image optimization is the process of adjusting high-quality web images to use the appropriate format, dimension, and resolution while keeping files as small as possible. It involves optimizing the image file size, aspect ratio, format, and more. Optimizing and adjusting images improves a website’s performance and rankings.
Why Is Image Optimization Important?
Optimized images help improve your website speed and overall performance, including its SEO rankings and user experience.
Let’s look at some more benefits of image optimization in detail.
Better Use of Resources
Large images consume more storage space and require more bandwidth for the files to be transferred successfully to users’ web browsers.
If you manage a website with limited resources, you’ll have to find a way to get the most of the limited disk space.
With image optimization, small website owners can significantly reduce the amount of bandwidth and disk space necessary to display and store their images. Site visitors will also benefit from it as optimized images will help reduce the page load time.
Another benefit of having a lighter website is that it will take significantly less time to create site backups.
Google has made page speed a crucial component of its ranking algorithm, favoring websites that load quickly and penalizing those with slow speed.
Websites with optimized media files will load pages faster – earning them a better chance to be discovered in Google Image Search. For testing site speed, use free tools like Google’s PageSpeed Insights.
Better User Experience
Another huge benefit from image optimization is the enhanced user experience. Combining fast page load and easy navigation, your site visitors are likely to stay longer to learn more about what you do, create, and offer.
The image optimization process includes adding alt texts to your images, which improves the site accessibility – we’ll discuss it more later in the article.
Image Optimization Tips to Improve Website Speed
In this section, we’ll go over several aspects that you need to consider for image optimization, such as the image format, file size, resolution, and more.
1. Choose the Correct File Format
The image format is the first aspect to consider in image optimization. Before we break down the different image formats, it’s important to note that they are classified into vector and raster images.
Vector file formats include SVG, PDF, EPS, and AI. Vector images typically work well for depicting images that are a combination of lines, points, and colors, like logos and icons. The main advantage of vector images is that you can scale them without compromising quality.
Meanwhile, raster images are pixel-based, which makes them resolution-dependent. It means raster images lose quality, becoming blurry or pixelated when resized. Image file formats in the raster category include JPEG, PNG, GIF, and RAW.
Let’s take a look at the most common file formats that work well on nearly all browsers and can be edited on most image editing software.
Notably the most popular image file format, JPEGs, are supported by nearly all devices and operating systems. Since JPEG images are relatively small, they don’t slow down web page load times and are quicker to upload or transfer.
JPEG files are also excellent at preserving color. However, since JPEGs use lossy compression, the smaller the file size, the lower the image quality. It is because each time a JPEG format is edited, it eliminates more data.
Therefore, this format won’t work well on images that require continuous adjustments and contain text – it’ll be difficult to read it after reducing the file size.
GIF files are 8-bit images that display a maximum of 256 colors. This means that GIF images are not as sharp in quality as other raster formats. Even though GIFs are not the right format for higher-quality images with a wide range of colors, they support transparency, simple line drawings and text, and produce small file sizes.
GIF is the best image format for creating animated images, which is an excellent way of creating engaging content.
Images in this format load rapidly and consume less bandwidth, so it’s a great alternative for sharing simple images on banner ads, blogs, and social media.
PNG (Portable Network Graphics)
Another popular file format for website images is PNG. PNG files can have up to 256 colors and support partially transparent images, capturing color information more efficiently than GIFs and displaying higher quality than JPEG images.
If you need to create or save images like logos, icons, simple illustrations, or any other that requires a smooth transition between colors, PNG images are a great choice.
In addition, the PNG format works well for images with a lot of text like screenshots, infographics, and banners. However, since this file format is bigger than JPEG, using too many PNGs files will slow down your page load time.
As a solution for improving lossless and lossy image compression, Google developed this image format. WebP combines characteristics of other popular web image formats, like replacing GIFs for animations and PNGs for transparency.
Unfortunately, several CMS (Content Management Systems) platforms do not support the WebP format. However, for users running a WordPress site using WordPress 5.8 or higher versions, it’ll be possible to upload WebP images to the media library.
2. Compress Your Image Files
When compressing image files, a critical point to remember is that smaller file sizes generally result in lower image quality.
Not only does image compression decrease storage and bandwidth usage, but it also provides faster page load and download times for site visitors.
However, you need to take into account the image’s content, color gradients, and detail complexity of the details when choosing how to compress images for the website without sacrificing quality.
An advantage of choosing raster files instead of vector images is that you can use either lossy or lossless compression techniques with raster images.
When you use lossy compression, some data is stripped out of the image, resulting in a smaller file.
On the other hand, lossless compression does not affect the image quality or clarity since it only removes non-essential data. If you need to use high-quality photos on the website, lossless compression is likely the best option, even if it means a slightly longer load time.
Here’s an example of the outcome of a lossless compression using ShortPixel.
Several image editing programs, including Adobe Photoshop, come with image compression tools. When compressing your images, ensure to implement the following best practices:
- Compress images prior to the upload. It is best to compress images before uploading them to your site. It helps you save disk space and speed up the upload process.
- Automate the image compression process. If you’re dealing with a handful of images, automatic compression may not be a priority. However, it is a great alternative for when you need to compress a large number of images simultaneously – saving you a lot of time. Automation also comes in handy for compressing images into different formats and naming the files.
- Tailor image compression to the device. Make sure to use the proper compression formats based on the targeted device. For instance, images with a lower resolution may still look great on mobile devices and help enhance the user experience on your website.
For existing images on your site, testing tools like GTMetrix will help identify which images need optimization.
To save even more storage space, check your site’s media library to remove unused images. If you use WordPress, plugins like Media Cleaner can help make the process more efficient.
3. Use Appropriate Image Dimensions
Image size and image dimension are two different things. The first refers to how much storage space an image takes up on your website – an image file size is usually measured in KB (kilobytes) or MB (megabytes).
On the other hand, image dimension refers to the width and height of the image based on pixels.
Using images with incorrect dimensions is an inefficient process and will slow down the website load speed.
For example, if you use a 500 x 500 px image for a 50 x 50 px thumbnail, the browser will have to download and scale the picture properly before displaying it to site visitors.
The best way to avoid that is by serving scaled images. Scaled images adjust to the exact dimensions required by the website, whether it is a full-width image or a small thumbnail.
To resize images to fit the site better, you can use offline tools such as Adobe Photoshop and GIMP or online image editors like PicResize.
While it’s possible to crop images using the WordPress media library or other built-in tools, doing it before uploading them to the site will avoid creating several versions of the original image and consuming additional disk space.
You can use your browser’s Inspect tool to discover the maximum display size of an image. Alternatively, there are several page ruler browser extensions you can install to measure different elements on a web page.
However, using a plugin may be a better alternative for websites with a large number of images – we’ll list the best image compression and optimization tools later in the article. If you’re a tech-savvy user, take advantage of the built-in developer tools in your browser.
4. Consider Serving Images via CDN
Using a content delivery network (CDN) to serve static content can significantly improve your website performance. Instead of relying on a single server to transport many megabytes of data for each visitor, a CDN provides global reach thanks to its network of data centers.
A CDN caches requested content and subsequently delivers it from a geographic location closer to the website visitor. This means the data travels a shorter path, which leads to faster load times for your website and all its media content.
Without optimizing your images, a CDN already speeds up the page load times.
In addition to a regular CDN, you can also use an image CDN. It can lower your site’s image payload up to 80%, resulting in a significant improvement in load speed and no noticeable decrease in image quality.
An image CDN can work well if you manage a dynamic website like an eCommerce shop or frequently upload new images. A few of the most popular image CDN providers include Cloudflare, Fastly CDN, and ImageKit.
Apart from the greater scalability and efficiency, let’s look at more benefits of using an image CDN:
- Enhanced user experience. Image CDNs automatically shrink images, converting their format according to the user’s device and image’s content. This is especially useful when accessing sites like eCommerce shops, which can display several thumbnail images on each web page.
- Better site speed. As long as your web images are stored in an image CDN, they don’t need to be optimized every time a new device requests to load them. This is because a CDN server uses caching, speeding up the time it takes to deliver images.
- Mobile-friendly. Advanced image CDNs ensure your images are properly displayed across all devices. To improve the image quality, an image CDN adapts and compresses the images according to the user’s device and network conditions.
- Constant uptime. Image requests are typically served by the most recently cached data. If the CDN server is down, the page will still load normally.
With all the benefits of serving images via a regular or image CDN, there remains one disadvantage – SEO.
If you use a CDN, from the search engine’s perspective, the image isn’t technically a part of your website as it’s physically located somewhere else. To avoid that, enable the CDN on a subdomain. That way, the SEO value from the images will still point to your site.
How to Take Advantage of Image Optimization to Boost Your SEO
Well-optimized images give your website a better chance of appearing in search engine results. Using the appropriate combination of format, alt text, and titles can all contribute to enhanced SEO performance.
You don’t have to spend many hours formulating and executing complex SEO strategies to optimize images. Boosting your SEO performance through image optimization involves a few easy steps.
Let’s look at several factors of image SEO to focus on so that search engines can crawl, index, and rank your images more efficiently.
1. Write Proper Image File Names
Descriptive file names help you and search engines like Google quickly locate images. That’s because correctly named files provide context about the images, increasing their chances of ranking in the image search.
Using the default names your camera assigns to each image is not a good practice. Google’s bots will not be able to tell much of a picture under the name shoes-image-01. A more appropriate and descriptive file name would be nike-tanjun-shoes-pink-white.
Depending on what kind of images you create or save, ensure to write the product name and include descriptive words such as its brand or color. Moreover, use dashes rather than underscores to name your files. For example, use white-shirt.jpeg instead of white_shirt.jpeg.
If you cater to an international audience and translate the site’s images, don’t forget to translate the file names as well.
When it comes to keywords, use a tool like Google Search Console to review your Search Analytics and the queries that include your products.
This will help you find what customers would type into a search engine if they were looking for the type of goods you offer. However, be careful not to overstuff it with keywords. Only use the ones that fit the context and naturally describe the image.
2. Write Alt Texts
Adding alt text is another technique to optimize your images and boost SEO. Essentially, alt text is a description of the image’s context and content. It’s what screen readers read and what will appear on the page if an image cannot be loaded.
In 2021, 26% of all images in the top 1 million websites did not have alt texts. In addition to accessibility and SEO improvements, adding them will also give you an advantage over competitors.
There are some practices to follow to write good alt texts:
- Be very specific. Ensure that your description is as specific as possible, including the image’s message, context, etc. However, note that you don’t have to describe images used for decorative purposes.
- Keep it brief. Try to keep your descriptions within 125 characters. Note that you don’t need to mention “image of,” “photo of”, or anything like that in your alt text as the HTML code has it covered.
- Use keywords. If possible, include a target keyword in the alt text. However, be careful not to overdo it.
3. Use Structured Data for Your Images
Another strategy for maximizing the impact of your SEO efforts is to leverage structured data or schema markup for your WordPress site .
Essentially, it offers clear information about your page to help search engines fully comprehend its purpose and context, improving the crawling and indexing processes.
That’s because structured data provides additional information about the images, helping search engines relate them to specific search queries, such as product details or even prices. By using structured data in your images, you increase the chances of them appearing in search results.
You can use Schema.org to structure data for improving the site’s SEO performance. This collaborative vocabulary helps you find specific markups for your page and code it properly.
In addition, it is important for site owners to follow all the general structured data guidelines that Google has laid out. If you fail to implement these standards, you can be penalized with poor rankings, or your pages will be ineligible for rich results.
Apart from images, structured data can be used for a variety of purposes, including:
- Knowledge graph. When you search for a person or business, Google gathers information from different websites and sources to display more relevant and useful results. Add information about your website to Google’s Knowledge Graph through structured data.
- Rich results. If your website contains several items that correspond to a specific search query, Google can display richer preview results by showing product reviews, star ratings, or videos. Rich results are an excellent opportunity to attract more targeted users to your page.
- Accelerated Mobile Pages. The main purpose of Google’s AMP project is to improve user experience on mobile devices, such as providing fast-loading pages. Using structured data in AMP can lead your website to be featured on mobile search as part of rich results and carousels.
4. Optimize the Page Title and Description
When ranking images, Google also considers components such as the page’s title, meta description, headers, and content.
Therefore, an optimized page title and description can help you rank in the image search. Conducting keyword research is a good place to start.
Tools like Ahrefs, Ubersuggest, and Semrush can help you identify the most relevant search queries, their search volume, and keyword difficulty.
Then, include the relevant keywords on your page title, meta description, and URL. Combined with other image optimization strategies, it’ll increase your site’s chances of ranking high on search results.
5. Place the Images Properly
Another important aspect of image optimization is where to place the images on the website. Adding images randomly can have a poor influence on the context and relevance of your page.
While it’s not uncommon to use images to break long texts, the image must be directly connected to the written content. Keep in mind that screen readers cannot access texts within the images, so make sure to provide relevant alt texts and include essential information in the image only.
Apart from improving accessibility, it also helps boost the page visibility on Google image search.
6. Optimize for Mobile Devices
Given that more than half of all web traffic comes from mobile devices, it is easy to see the importance of ensuring visitors can access all pages and images smoothly from all devices.
Google’s Mobile-Friendly Test Tool scans your website and evaluates whether it will look good on mobile screens. In addition, the tool will provide a report on the overall usability of your website.
For example, if the page only loads partially on a mobile device, it’ll inform which elements, including images, have issues and need to be fixed.
Check our comprehensive guide for tips on making your website mobile-friendly.
7. Use Copyright-Free and Good Image Quality
All images uploaded to your site must be copyright-free to prevent the risk of lawsuits, which would not only damage your online reputation but also the site’s rank on search results.
Shutterstock, Unsplash, and Getty Images are among the most prominent stock image providers. These websites contain thousands of free-licensed images for different purposes.
Alternatively, navigate to Google Images’s Advanced Search section and find images based on different Usage Rights.
As part of your image optimization workflow, consider creating original and unique images for the site.
Especially if you run an eCommerce store, high-quality product images generate higher engagement and help drive sales.
5 Best Image Optimization Tools
Manually optimizing a large number of images from your media gallery can be a time-consuming process. Luckily, many online tools are available for optimizing your images and improving site speed.
Let’s take a look at five options worth your attention:
This image optimization tool supports various image formats, such as JPEG, PNG, GIF, and even PDF files.
Based on the image size and dimension, ImageRecycle can determine which images on your website need adjustments. All you have to do is enter your website address, and the tool will send a free report to your email.
This image optimizer provides numerous ways to optimize images, such as reducing the image file size and using smart lossy compression techniques.
However, Kraken’s free web interface has an image size limit of 1 MB. For a bigger limit and more advanced features, you can opt for one of Kraken’s premium plans.
Alternatively, WordPress users can take advantage of the Kraken.io Image Optimizer plugin.
This free online image optimizer offers numerous image editing tools. You can convert file formats, adjust the image file size, add a watermark, and many more.
iLoveIMG allows you to optimize images from your computer, Google Drive, or Dropbox.
This image optimizer shrinks images to the minimum possible size without compromising their quality. It supports JPEG, JPG, GIF, and PNG formats and lets you simultaneously resize up to 20 files.
Additionally, you have the option to control the degree of compression applied to the images.
With the Bulk Smush feature, this WordPress plugin for image compression can optimize up to 50 images in one click.
Smush lets you set the maximum image resolution for file formats such as PNG, JPEG, and GIF and comes with a lazy-load feature to improve site performance.
Opting for the premium version of this WordPress plugin, you can convert images to WebP and access additional image optimization tools.
Looking to Optimize Images for WordPress?
Having a website means that you will have to be ready to adapt it to changes in search engine algorithms, technological advancements, and the evolving expectations of users. This also applies to all of the images put up on your website.
Since modern internet users are quickly drawn to visual content, it is easy to see why image optimization is one of the key variables that contribute to your website’s overall performance.
Reduced user satisfaction, slower page load times, greater bounce rates, and fewer leads are all possible consequences of not optimizing your website’s images. Not only high-quality image optimization helps build your brand’s authority online, but it also improves its position in search engine rankings.
With image optimization plugins or online tools, you can easily optimize your images in just a few clicks. You can reduce large image files significantly without compromising their quality.
Bear in mind that optimizing images is only one component of providing an excellent user experience. You can further enhance the overall quality of your website through elements such as security, trustworthiness, and accessibility.
We hope that the tips provided in this guide can help you take advantage of the benefits of optimization both for your website’s page load speed and its image SEO performance. Good luck!