Optimising Images for the Web: A Guide for Designers

Optimising Images for the Web: A Guide for Designers

Slow images are a silent profit killer.

Every unoptimised image on your website is actively costing you money by killing your conversion rate and destroying your search engine ranking.

Optimising images for the web isn't a “nice-to-have” skill; it's a non-negotiable system for building a faster, more profitable website.

This isn't a list of random tools. It's a strategic breakdown of the techniques you need to protect your bottom line.

Why Image Optimisation Matters

Before knowing how to optimise images, let's see why optimising images for the web is essential. There are several reasons to optimise your images:

Faster load times: Images with large sizes could slow down your website, leading to a poor user experience. Optimising photos will reduce the file size and improve load time.

Better SEO: Google considers page speed when ranking websites. Optimising your images can improve your page speed and search engine rankings.

Improved user experience: Users are more likely to stay on your website if it loads quickly and smoothly. Optimising your images can improve user experience and keep visitors on your site longer.

The Impact of Image Optimisation on Core Web Vitals

Look, it's not just about making a site feel fast. Google measures this stuff with something called Core Web Vitals. These are real-world metrics that score your user experience, and they have a direct impact on your search rankings. Getting your images right is a massive part of getting good scores.

Largest Contentful Paint (LCP)

LCP basically measures how long it takes for the biggest thing on the screen to load. Nine times out of ten, that's a big hero image or a banner. If that image file is huge, your LCP time will be awful, and users will just see a blank space while it struggles to appear. A slow LCP tells Google your site is sluggish. Compressing your images properly and using modern formats fixes this. It's a no-brainer.

Cumulative Layout Shift (CLS)

Right, you know when you're about to tap a button and the whole page suddenly jumps because an image loaded above it? That's a layout shift, and it's incredibly annoying. CLS measures how much your content moves around unexpectedly. This happens when the browser doesn't know how much space to save for an image.

The fix is simple: always include width and height attributes in your image tags. This lets the browser reserve the correct space from the start, so nothing jumps. A stable page means a happy user and a better CLS score.

Understanding Image Formats: Image formats determine the quality and size of the images; three main image formats are used on the web: JPEG, PNG, and GIF.

1. JPEG: JPEG (Joint Photographic Experts Group) is the commonly used image format on the web; It's best for more complex images that require many colours. A JPEG image is smaller, making it the best fit for the web.
2. PNG: PNG (Portable Network Graphics) is one of the most popular image formats used on the web. This image format is best for images like logos and icons. Typically, these files are larger than JPEG format files, but they offer better quality and compression.
3. GIF: GIF (Graphics Interchange Format) is an older image format, and it's being used on the web. It's best suited for simple images with few colours, such as animations and logos. GIF files are small and support animation, making them ideal for web use.
4. WebP: Thing is, JPEG and PNG have been around forever. WebP is a modern format from Google that's just flat-out better for the web. It offers much smaller file sizes than JPEG, often around 25-35% smaller for the same visual quality. It also supports transparency like a PNG and can even handle animations, making it a great replacement for GIFs. All modern browsers support it, so there's really no reason not to use it.
5. AVIF: If you want to be on the cutting edge, AVIF is the next step up. It's an even newer format that offers mind-blowing compression. We're talking about images that can be 50% smaller than a JPEG without you noticing any difference in quality. It's perfect for getting your page load times as low as humanly possible. Support is good across the latest versions of Chrome, Firefox, and Safari. For complete coverage, you can use the HTML <picture> element to provide a WebP or JPEG as a fallback for any older browsers that might not be up to speed yet.

Choosing the Right Image Format

Now that you understand the different image formats, let's discuss choosing the right one for your web images.

Use JPEG for photographs and complex images.

If you're working with photographs or complex images with many colours, use JPEG. This format lets you maintain the image's quality while keeping the file size small.

Use PNG images if you need transparency.

Transparency images are images like Logos and icons, etc. PNG format supports transparent images and helps maintain image quality while keeping the file size relatively small.

Use GIF for simple images with few colours.

Use GIF if working with simple images with few colours, such as animations or logos. This format supports animation and keeps the file size small.

Tools for Optimising Images for the Web

Several tools are available in the market that help you optimise your images for the web. Here are the best and most affordable options:

Dmarketingacademy.com

Dmarketingacademy.com is an online Free customised Image Compression Tool that supports all image formats like JPG, JPEG, PNG, etc. You can compress the large image to a custom size without compromising the quality of the picture. It effectively compresses images to 200 KB and even below.

Adobe Photoshop

Adobe Photoshop is a powerful image compression tool that allows you to resize and compress image file size. It also has the feature to save images for the web and automatically optimises the file size.

TinyPNG

TinyPNG is an online image compression tool that uses lossy compression techniques to reduce file sizes without compromising image quality. It supports both JPEG and PNG files.

Kraken.io

Kraken.io is an online image compression tool that uses powerful algorithms to reduce file sizes. It also supports all three formats: JPEG, PNG, and GIF.

Cloudinary

Cloudinary is an image optimisation tool that allows one to upload, store, and deliver images. It also has automated image optimisation features, as well as it supports responsive images and lazy loading.

Compressor.io

Compressor.io is also a free online image compression tool that supports all formats. Like TinyPNG, Compressor.io also uses a lossy compression technique to reduce file sizes without compromising quality. It's easy to use compared to other tools because of its drag & drop interface.

Squoosh

Squoosh is a free image compression tool developed by Google. It supports all image formats, including JPEG, PNG, JPG, etc. Using these features, you can adjust the image quality and compare them differently.

Compression Techniques

Image compression is the process of reducing the size of an image file without losing its quality. Let's see the compression techniques to optimise web images.

Resize your images

The larger the size of the image, the longer it will take to load. Resizing the photos with the correct image dimensions will support and improve the load time. It's essential to resize your images to the right size.

Use image compression software.

Many software tools in the market can help you compress your images without compromising quality.

Use image sprites

Image sprites are a collection of combined images to form a single image. Image sprites could reduce the HTTP requests needed to load the pictures. This will help to improve your site performance.

Use a content delivery network (CDN)

A content delivery network (CDN) helps to improve your site's load speed. By enabling CDN, it will save your website information on all the servers. If a user accesses your site, the data will be served from a closer server to the user. So, it will improve the site load speed and reduce the load time.

Use vector graphics

Vector graphics are created using mathematical equations and are resolution-independent. Using VG, you can scale up or down the images without losing their quality (lossless compression). It is best suited for logos, icons, and other graphics. Also, photos will be very clear on all devices.

Consider the image format.

As you have seen earlier, many image file formats exist, like JPG, JPEG, SVG, GIF, and PNG. Every format has its pros & cons; choosing the correct format will improve the quality of your images. For example, JPG is best for photographs, PNG is best for images with transparent backgrounds, and Vector graphics SVG will be the best format.

Use lazy loading

Instead of loading everything, lazy loading will load certain things when needed. This will load one part of your website at a time as the user scrolls the page. Based on your CMS, you could enable it using different methods to improve loading speed. For example, WordPress sites have many plugins like Nitropack, WP-Optimise, etc.

Minimise HTTP requests

The browser raises HTTP requests to your hosting server to load your site. More HTTP requests longer it will take to load. CSS stripes effectively combine multiple images into a single file, helping minimise the HTTP request.

Consider image caching

Caching is storing the website's data in the user's device. By holding it, data can be quickly retrieved when the next time the user visits. Enabling image caching will improve the website's performance and reduce the load time. Cache plugins are available for WordPress sites.

Use responsive design

Responsive design means the website is user-friendly on all devices, such as laptops, mobiles, tablets, etc. By making a responsive design, you can ensure your images look great and are well-optimised for all screen sizes.

Implementing Responsive Images with srcset and sizes

Making a site “responsive” isn't just about the layout squashing down to fit a phone. It's about performance, too. Forcing a tiny mobile device to download a massive image designed for a huge desktop monitor is lazy, wastes data, and makes your site painfully slow for that user.

Use the `srcset` attribute to provide options

This is where the srcset attribute comes in. Instead of just one image file in your src, you give the browser a list of different-sized versions of the same image.

You're basically saying, “Here's a small, medium, and large version. Pick whichever one works best for you.” The browser is smart enough to look at the device's screen resolution and pixel density (for those fancy retina displays) and download only the most suitable one. No more wasted bandwidth.

Use the `sizes` attribute to give the browser hints

The sizes attribute works alongside srcset to make the browser's job even easier. It tells the browser how much space the image will actually take up on the screen at different viewport widths.

For example, you can tell it, “This image will be 100% of the screen width on devices up to 600px wide, and 50% of the width on anything wider.”

This context helps the browser choose the right image from your `srcset` list more accurately and much faster, sometimes even before the main CSS file has finished loading. It's a proper game-changer for performance.

Here’s how it looks in practice:

<img src="small-image.jpg" 
     srcset="small-image.jpg 500w, 
             medium-image.jpg 1000w, 
             large-image.jpg 1500w"
     sizes="(max-width: 600px) 100vw, 50vw"
     alt="A descriptive alt text for the image">

In this example, the src is a fallback for very old browsers. The browser will then choose the best option srcset based on the rules in sizes.

Optimise for mobile devices

As per a recent survey, there are 5.56 billion Internet users worldwide in 2025.

More than 85% of people use the internet on mobile devices. Websites need mobile optimisation to survive in this market. To make your images responsive to mobile devices, use smaller image sizes for mobile devices.

Use image compression plugins.

If your CMS is WordPress, you can use many available plugins, which help to optimise your images. Advanced compression algorithms of these plugins help reduce the file size and optimise images.

Use image lazy loading plugins.

As mentioned earlier, enabling lazy loading improves your website performance and reduces the load time. Plugins like Nitropack and WP-Optimise provide this feature for free.

Optimise image metadata

Image metadata includes information about the image, such as filename, caption, and alt-text. By optimising your images, metadata helps to improve your website's SEO performance. This will make your images accessible to users with visual impairments.

Use image optimisation tools.

There are some free online tools, like Dmarketingacademy's image compression tool, kraken.io will help you to reduce the file sizes of your images. These tools not only help to compress but also help to convert the images to other formats.

Test your website's performance.

Monitoring your website's real-time performance is very important. It was one of the proven ranking factors of Google. You can use free tools like Google Page Speed Insights to analyse your website's performance and identify improvement areas.

Consider image placement

The placement of your images on a webpage can also affect load times and user experience. To improve website performance, consider placing images below the fold or using lazy loading to delay their loading until needed.

Consider the image subject.

The subject of your image can also impact its optimisation. According to your embodiment subject, your file size can be determined. If your file has a simple subject, it will reduce the file size without losing the quality of the image.

Avoid using too many images.

While images are essential for engaging users and communicating information, too many images can slow down your website and overwhelm your visitors. Consider using text or other visual elements instead of images when appropriate.

Use consistent image styles.

Consistent image styles can create a cohesive design and improve user experience. This can include using similar image sizes, colour schemes, and typography across your website.

Use appropriate file names.

While using images, add keywords related to your pictures in the file name. This can help to improve your SEO performance. Using keywords in image file names will rank your images on Google's image search results.

Use alt text

Alt text is a piece of information about the image. It helps visually impaired users to understand what the image is. Adding your targeted keyword relevant to the image is one of the on-page SEO elements.

This will help the visually impaired and search engines better understand the value of the image to the content.

Optimise thumbnails

Thumbnails are like a preview of your content before you click on it. To optimise your thumbnails need to be sure of the file sizes and that their formats can be loaded quickly.

Monitor image loading times.

Monitoring Image load time is one of the essential aspects of Technical SEO. By reducing the load time, you can optimise the load speed. Using GA, you can track the page load times and spot the areas of improvement.

Use appropriate image quality.

Optimising images for the web is a challenging task. During the process, you must focus on Quality and file size. Using the original image will result in a larger file size.

The usage of small file-size images will result in lower quality of the image. So, finding the balance between the quality and file size is vital to optimise the images.

Use web-safe colours

Web-safe colours are the 216 hues that can be displayed on any computer or device. Using web-safe colours ensures your images are consistently shown across different devices and browsers.

Avoid using image sliders.

While image sliders can be visually appealing, they can also slow down your website and create a poor user experience. Consider using static images or other visual elements instead of image sliders when appropriate.

Use image galleries

Image galleries can be used to display multiple images in an organised and visually appealing way. Consider using image galleries instead of numerous individual photos when appropriate.

Use web fonts

Web fonts are used as substitutes for images. It was designed for use on the web and could create more visually appealing text elements.

Use image sitemaps

Sitemaps are the structure of your web pages. Google can easily understand your website using sitemaps. An image sitemap is one type of sitemap that consists of information about images on your website. This can effectively be used to optimise your site's SEO performance.

Use SVG images

SVG images are vector images that can be scaled without losing quality. They can be used for your website's logos, icons, and graphics.

Consider the context

The context in which the images will be seen is essential to understanding.

For instance, if your website is geared towards photographers or graphic designers your website is geared towards photographers or graphic designers, for example, they would anticipate larger, higher-quality photos.

On the other hand, smaller and more compressed images can be more acceptable if your website is meant for a broad audience.

It's critical to keep up with the most recent web design trends and approaches and follow the advice above.

New tools and technologies are continually being developed, and the web design business is constantly changing.

You can make sure that your website designs are continuously optimised for the optimum user experience by remaining informed and continuing to learn.

Reduce the colour palette.

Using limited colours or reducing the number of colours used in the images could reduce the file size. This technique works best for simple images and reduces their file size without losing quality.

Best Practices for Web Images

In addition to understanding image formats and compression techniques, you should follow a few best practices when optimising your web images.

Use descriptive filenames

Descriptive filenames help search engines to understand your images better. Also, it helps to

Use the Right Image File Format

Choose the correct file format for each image. For photographs or images with many colours, use JPEG. For images with transparent backgrounds or simple graphics, use PNG. For animations or simple graphics with few colours, use GIFs.

Reduce Image Size

The larger the image size longer it takes to load. Making your images the correct dimensions would lower the size. You can use Image compression tools to reduce the size further.

Optimise Alt Tags

Alt tags describe images for visually impaired users and search engines. Use descriptive alt tags that include relevant keywords to improve your SEO.

Best Practices for Image Optimisation

Here are some of the best practices other than using tools to optimise it for the web:

Start with High-Quality Images

Starting with high-quality images with large file sizes will help save space. Starting with high-quality images also ensures the final output image looks good.

Test Your Images

Test your images on different devices and browsers to ensure they load quickly and look good. You can use tools like Google PageSpeed Insights or GTmetrix to test your website's performance.

Balance Image Quality and File Size

It's crucial to balance image quality and file size when optimising images. As much as you maintain the quality and size of the image, it will help both website SERP performance and User performance.

Keep Your Image Library Organised

Keep your image library organised using descriptive filenames and sorting images into folders. This can make it easier to find the pictures in the future.

Conclusion

Image optimisation is an essential step in designing a website that loads quickly and looks fantastic.

You can make sure that the photos on your website look great and load quickly by knowing the various image formats, picking the appropriate quality, resizing images, and optimising file sizes.

Remember that in mind that both user experience and search engine optimisation depend greatly on website performance.

You may enhance the functionality of your website and provide your users with a better browsing experience by optimising your images for the web. Take the effort to optimise your images to benefit from a quick and attractive website.

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