The Ultimate Guide to Optimising Images for the Web in 2025: Speed, Quality, and SEO Tips

Website performance is critical for your business’s success. The time you have to grab someone’s attention online is shrinking year on year.

It’s said that a picture is worth a thousand words and nowhere is this more true than in online content. 

Visually engaging content and image optimisation are a vital part of any website’s management.

And with search engines prioritising fast-loading sites, along with Artificial Intelligence (AI) cutting into the online search space, you need to have eye-catching content that loads fast if you’re to capture that attention gold-dust.

They’re easy to overlook, but images affect your site’s speed, user experience (UX) and SEO ranking.

Optimising your images for the web ensures improved page load times. It helps your site’s visual appeal and on-page SEO success too.

By this point, you might be thinking “sounds good, but what do you mean exactly by image optimisation?”

Allow us to explain.

What is Image Optimisation?

Image optimisation is the process of reducing an image’s file size without affecting its quality.

It’s about finding the perfect balance between image quality and website performance.

If done well, images can be visually appealing without affecting your website’s ability to be quick.

Not only that, but search engines favour websites that load fast and they reward them by ranking them higher in search engine results pages (SERPs).

A core part of optimising images is compression. And there are two main methods of applying this; lossy and lossless.

Lossless Compression

This method reduces the file size without affecting the quality. 

It keeps hold of all the image data which makes it perfect for graphics, logos and images that need transparency, such as PNG files.

You’re best using this method if you need high-quality images that keep all their original detail.

Lossy Compression

In comparison, this method produces much smaller file sizes by removing some of the image data.

However, there is a price to pay for this size reduction and that’s less detail than before compression.

This method still has its place though. You’ll want to use it mainly for pages that need fast loading, such as blog posts.

A popular lossy format is JPEG due to its balance of quality and size.

Both these compression methods have their place and it’s up to you to decide which one you want to use for your particular use case.

But is it really worth putting your energy into this technical jargon when all you want to do is focus on your business?

The answer is yes and there are very good reasons why. 

Let’s start with optimised images for SEO.

Why Image Optimisation is Crucial for SEO success

It’s not obvious on the face of it, but image optimisation plays a crucial role in where your website appears on SERPs.

Site speed, mobile usability and accessibility are all taken into account by search engines before they offer your page up to the public’s questions.

Let’s look at some of the ways optimising your images can boost your rankings.

Faster Page Load Times

A common reason for slow-loading websites is large, unoptimised images.

This directly impacts your site’s bounce rate. In fact, a page that takes 10 seconds to load has a 123% higher bounce rate than a page with a one-second loading time.

A high bounce rate combined with a slow-loading page is a death sentence for your SEO ranking.

You’ll want to avoid that. Improving your website’s speed is a good way to go about this and image optimisation is a great place to start.

Enhanced User Experience (UX)

This directly ties to your site speed. 

Your site visitors can probably tolerate the occasional typo, dodgy graphic or weird functionality.

What they absolutely cannot tolerate is a page that takes a millennia to load. 

Optimising your site images can help you avoid this.

Increased Visibility in Image Search

Visual search has become the main method of online browsing for a large number of users.

50% of online shoppers say images on Google helped them decide what to buy. 

This trend will likely increase in the coming years with devices like Google Lens and Apple Vision.

It’s a safe bet to assume that these images driving conversions are highly optimised for performance.

They’ll also contain descriptive alt text, file names and captions.

This is something to especially keep in mind if your business sells products online. You may have product pages tucked away in dire need of some optimisation.

Now might be the time to blow the dust off them and set them up for maximum SEO impact.

Improved Accessibility and Inclusivity

Making sure your website caters to a diverse set of user needs is also something you’ll want to focus your attention on.

Sites that get this right tend to rank better in SERPs. 

For example, optimising your images with accurate alt-text and captions will allow users who rely on screen readers to have a better experience of your site. 

This is good practice in general, but it’s also a ranking factor and lets search engines know your site will provide a user-friendly experience for as many people as possible.

Reduce Bounce Rates and Higher Engagement

We’ve mentioned bounce rates already, but it bears repeating.

Slow loading speeds are something you want to avoid and unoptimised images are often a big contributor to this problem.

Search engines are aware of your site’s bounce rate and a high bounce rate indicates your content isn’t valuable or relevant.

Conversely, a low bounce rate is a strong signal that your site has something valuable to offer and that people want to see what’s on it. Up the rankings you go!

It’s also worth mentioning that implementing a lazy loading technique alongside your optimised images is a great way to improve your site’s speed. We’ll detail this further below.

Higher Conversion Rates

This is what we’re all after for our businesses. Turning traffic into customers who want to buy from you.

Optimised images may not seem particularly impactful here, but they are.

Not only do they improve your SEO which will help with traffic in the first place, but they help increase user trust once this additional traffic is on your site.

How? By making a great first impression. Not only will your site be fast loading, but it will also have high-quality images of your infographics, products or blog decoration.

By optimising your website images, you’re not just improving aesthetics that no one will see.

You’re taking active steps to improve your site performance which makes it faster, more accessible and more user-focused.

Think of it like an investment. Not an investment that’s great for social media clout, but a slow, high yielding one that complements your overall portfolio and pays for itself in the long run.

Best Practices for Image Optimisation

To get the best from your image optimisation efforts, you need to combine techniques with practical tools.

A Lot of the work has been done for you here and there are a number of best practices to follow.

Let’s take a look at a few.

Use Descriptive, Keyword-Rich File Names

When a search engine looks at your site, they don’t see images. They see file names.

That’s why using focused keyword file names can be so beneficial for your on-page SEO improvements.

It increases the chance of your images appearing in SERPs.

As an example, don’t leave the default names like “IMG1234.jpg” when you upload an image to your website. 

Instead, rename it with something descriptive like “fast-loading-web-design-example.jpg.”

Compress Images Without Sacrificing Quality

As you’ve already seen, reducing the file size of your images helps to improve your site speed.

Compression tools are what you will use to reduce your file sizes and you can apply either lossy or lossless compression.

Your compressed images will then contribute to your faster site, improved user experience and lower bounce rates.

Choose the Right Image Format

Image format also plays a role in your website’s performance alongside your image compression.

Different format types provide different benefits. The below infographic gives you an easy to read comparison:

 

Resize Images for Your Website

You’ve seen that large image file sizes can affect your site’s performance.

Well, overly large images as they’re seen on the page can have the same effect.

You’ll want to resize your images before adding them to your site so their dimensions are exactly what you need.

For example, 1200px wide images are often enough for blog posts.

It’s a good idea to ensure the web builder you’re using or developer uses a ‘srcset’ attribute so that your images can be dynamically resized for different device viewports.

Add Descriptive Alt Text

Like your image file names, search engines also see your Alt-text.

This text helps them understand what your image is and improves accessibility for visually impaired users.

Here are a few tips for writing strong Alt-Text:

• Be concise and clear in your image description
• Include relevant keywords, but don’t keyword stuff
• Focus on relevance to the page’s content

For example, rather than something generic like “image of cup” write “high-quality ceramic coffee mug with stylish handle.”

Here’s a visual example:

Implement Lazy Loading

This functionality delays your image loading until they need to be visible to the user.

They’re essentially hiding until they’re needed. You’ll have better perceived loading times and a reduced initial load time after implementing this.

This is great for your website visitors as they’ll see the content they’re looking at faster which ultimately means a better experience and lower bounce rates for you.

Most website builders and hosts allow for lazy loading as standard in their templates, but there are tools for WordPress sites too:

1. LazyLoad
2. A3 Lazy Load
3. Smush
4. Optimole

Use Image Sitemaps

Think of this like a blueprint for all the images on your site.

It gives search engines what they need to discover and index your images quickly.

This is particularly useful for e-commerce websites with hundreds of product pictures.

Again, most website builders submit your image sitemap when you go live and request indexing.

 You can keep an eye on the progress of this in Google Search Console.

Test and Monitor Image Performance

Unfortunately, image optimisation isn’t as simple as ‘set it and forget it.’

To keep your website at the top of its game, you will need to consistently evaluate how your images are performing across your pages.

Fortunately, there are tools that can help with this like Lighthouse and Google Analytics. 

The key metrics to keep an eye on are loading times, bounce rates and engagement rate.

This regular monitoring will allow you to identify and fix any issues or bottlenecks and keep your site as fast as possible.

Implementing these best practices will ensure your website remains fast, ranks higher in SERPs and provides your users with a seamless experience.

They’re a simple, but important piece in allowing you to remain competitive online.

Advanced Techniques for Image Optimisation

So, let’s say you’ve implemented all of the above image optimisation best practices, but you want to go a step further.

You have options. Some are new techniques and some are a deeper look at best practices you’ve already seen.

Let’s dive in.

Leverage Next-Generation Image Formats

Modern image formats like WebP and AVIF deliver high-quality images at a fraction of the file size traditional formats can provide.

These modern formats are supported by most browsers and are becoming more popular for all high-performance websites. 

WebP offers both lossy and lossless compression and offers images 25-34% smaller than JPEGS. AVIF goes even further and produces file sizes even smaller than WebP.

Don’t worry if your site images aren’t in these modern formats yet though. A lot of the internet still relies on JPEGs and PNGs. 

There are some tools you can use to convert your traditional images into WebP or AVIF formats.

Tools like Squoosh and Cloudinary. 

Implement Responsive Images

Responsive images are ubiquitous online now and you probably expect them when you visit a site on your laptop or mobile.

In fact, it can be quite jarring if you switch from one device to another and the same website is completely different or not working at all.

It’s a crucial practice to get right when optimising your images. Thankfully, it’s quite easy.

Most website builders can take care of it for you. If not though, there’s an easy way for you to set responsiveness up via your HTML.

You just need to use the <picture> element or the ‘srcset’ attribute in your HTML document to define multiple versions of an image.

For example:

 

Apply the Blur-Up Technique

The Blur-Up Technique is a useful way to hide a slow page loading speed.

The technique allows you to display a low-quality, blurred version of an image as a placeholder while your high-resolution image loads in the background. Here’s an example:

It’s very effective for a two reasons:

1. It reduces the appearance of white spaces during loading
2. It provides users with a seamless visual transition to the full images

Again, your website builder will likely provide a way of implementing this technique.

Alternatively, you could use tools like Cloudinary or Lighthouse which allow you to automate the blur-up process.

Optimise Images with Content Delivery Networks (CDNs)

CDN’s help distribute your website images across multiple servers.

Many advanced CDN’s offer real-time image optimization. They can automatically resize and compress images based on the device used and the user connection speed.

They can also cache images closer to a user’s location by utilising multiple servers worldwide.

Some popular CDN’s for you to check out are Cloudflare, AWS CloudFront and Akamai.

Utilise Image Caching to Improve Performance

Image caching is a technique that stores copies of your site’s images in temporary storage locations.

These locations can be a user’s browser or a CDN. The main benefit of caching is to improve your page load speeds. 

Everytime a visitor returns to your site the images can be shown quicker as they don’t need to be reloaded from the server.

How does Image Caching Work?

When someone visits your site, their browser asks your server for images and other assets that make the site a site.

With caching, these assets are temporarily saved in the user’s browser or an intermediary server like a CDN.

If the same person visits your site again their browser can retrieve the images from the cache instead of requesting them from the server again.

Benefits of Image Caching

• Faster Page Load Times: Cached images load almost instantly on repeat visits

• Reduced Server Load: Your server is spared repeated requests from visiors

• Enhanced User Experience (UX): The experience of your website is smoother for your user

• Improved Mobile Performance: Bandwidth usage of mobile data is minimised. This means faster image loading for users with limited data plans

• SEO Boost: As you know, faster page loading results in improved SERP rankings

Best Practices for Implementing Image Caching

You have a few options to choose from here.

You can set Cache-control headers in your HTML. This specifies how long a browser should cache your images for.

Alternatively, you can use a CDN which caches your images on multiple servers around the world. 

If you’re site runs on WordPress then there are a number of plugins you can utilise like W3 Total cache or WP Rocket.

Once you’ve implemented image caching via your chosen method you can test its effectiveness with tools like Google PageSpeed Insights or GTMetrix.

Common Caching Mistakes to Avoid

• Forgetting to invalidate stale caches: if you update an images but forget to invalidate the cache then users might still see the old image. You can fix this issue with cache-busting techniques.

• Caching too many dynamic images: dynamic images (images that change frequently) can overwhelm your cache if not managed effectively. You can use micro-caching to eliminate this issue.

• Overlooking mobile-specific caching: make sure your caching strategy works well with mobile data. Tools like WP rocket can handle this for you.

By implementing the above techniques you can increase your page speed, reduce your server load and offer your users a seamless experience.

But it’s no good being armed with best practice if you don’t have all the tools to implement, right?

Fear not. We’ve created a useful list of the best image optimisation tools below just for you.

Tools and Plugins for Image Optimisation

Squoosh

An open-source image compression tool created by Google. 

Key Features:

• Supports modern formats like WebP and AVIF
• Allows manual adjustment of compression settings
• Works offline as a Progressive Web App (PWA)

Best For: Beginners and those working with small image batches.

TinyPNG

One of the most popular online tools for compressing PNG and JPEG images. It uses a lossy compression technology.

Key Features:

• Drag and drop interface for easy use
• Batch processing of up to 20 images at once
• WordPress plugin for automated optimisation

Best For: Bloggers and small businesses managing visual-heavy sites.

ShortPixel

A versatile image optimisation tool that supports a variety of formats such as JPEG, PNG, GIF, WebP and PDF. It integrates with WordPress too.

Key Features:

• Offers lost and lossless compression
• Converts PNG and JPEG to WebP automatically
• Optimises existing media libraries and serves responsive images

Best for: WordPress websites and developers handling large libraries of images.

Smush

A WordPress plugin designed to optimise images without affecting quality.

Key Features:

• Compresses images up to 5MB for free
• Lazy loading feature for faster initial page loads
• Automatic optimisation of newly uploaded images

Best For: WordPress users looking for a free, all-in-one solution.

EWWW Image Optimiser

An image optimiser that offers advanced features for compressing and optimising on WordPress sites. 

Key Features:

• Unlimited file size for compression
• Supports next-gen formats like WebP
• Advanced settings for developers

Best For: WordPress developers needing customisable and automated solutions.

Cloudinary

A cloud-based platform that manages, optimises and delivers images.

Key Features:

• Real-time image transformation and resizing
• Supports advanced techniques like lazy loading and blur-up
• Integrates with CDNs

Best For: Large-scale websites and e-commerce platforms

ImageOptim

A desktop application for macOS that offers lossless compression for JPEG, PNG and GIFs.

Key Features:

• Removes unnecessary metadata from images
• Keeps original quality with reduced file sizes
• Drag and drop

Best For: Designers and developers preparing images offline.

Adobe Photoshop

A powerful tool for advanced users. 

Key Features:

• Adjusts image quality and dimensions manually
• Supports exporting images in WebP and other formats
• Provides editing capabilities 

Best For: Professional designers and content creators.

As you can see from this list, the best tool to use depends on the platform you use, the scale of your site and your technical prowess.

WordPress users will benefit from Smush and ShortPixel whereas Cloudinary may be more useful if you’re working with a cloud-based solution.

TinyPNG is still king for simple compression tasks and Squoosh is a close competitor.

Avoid Common Mistakes in Image Optimisation

Now that you have as much information on image optimisation that you can stomach, you may feel like a world authority on the topic.

Not quite yet. We still need to cover what not to do.

Below are some common mistakes and how to address them.

Uploading Oversized Images

A frequent mistake is to upload images with large file sizes and dimensions.

Why It’s a Problem

• Causes slow loading times and leads to higher bounce rates and lower engagement
• Harms your search rankings due to search engines penalising your slow site

Solution

• Resize your images to fit the relevant display dimensions
• Use tools like Squoosh, Photoshop and ShortPixel to reduce file dimensions
• Implement responsive design with the ‘srcset’ attribute

Over-Compressing Images

Compression is important for optimising your images, but you can have too much of a good thing.

Overdoing it can result in poor image quality.

Why It’s a Problem:

• Pixelated or blurry images can make your site look unprofessional
• Visitors may leave quickly if the quality doesn’t meet their expectations

Solution:

• Balance your compression with quality by testing different compression tools
• Tools like TinyPNG, Cloudinary or ImageOptim can help you find the right sweet spot

Ignoring Alt Text

This is the text that lets search engines know what your image is.

Without it, they can’t understand what each image is about.

Why It’s a Problem:

• Negatively affects your rank in image search results
• Visually impaired users won’t be able to understand your image content

Solution:

• Add concise, but descriptive Alt text for all your images, including keywords
• Don’t go crazy with the keywords though. Focus on accurate descriptions of the image content

Using Incorrect File Formats

The different formats have their various uses.

Choosing the wrong one for your purpose can affect its quality, size and usability. 

For example, using a PNG for a photo or a JPEG for your logo can result in unnecessary bloating and quality loss.

Why It’s a Problem:

• Large file sizes increase loading times
• Some formats don’t support features you need, like transparency for certain designs

Solution:

• Use the right format for the job:
• JPEG: best for photos where file size is more important
• PNG: ideal for images requiring transparent e.g. logos
• WebP/AVIF: best for high-quality compression and modern performance
• SVG: for scalable graphics like icons and logos

 

Neglecting Image Metadata

Your images will often include metadata such as camera settings, GPS location or file creation date.

This adds to the file size even though it can’t be seen.

Why It’s a Problem:

• Unnecessary data which slows down your pages
• Can inadvertently share sensitive information such as location data

Solution:

• Use tools like ImageOptin or Photoshop to strip the unnecessary metadata 

Failing to Monitor Performance

It’s easily done, but forgetting to monitor the performance of your optimised images is a mistake to be avoided.

Why It’s a Problem:

• Unoptimised images may creep their way back into your sites and slow it down over time
• You can miss opportunities to refine and improve your existing image practices

Solution:

• Audit your site regularly using tools like Google PageSpeed Insights or Lightouse
• Set up automated alerts to track performance metric changes

Skipping Lazy Loading

Failing to implement lazy loading into your images is just another way to increase your page loading times.

Why It’s a Problem:

• Users will have to wait longer to see your content
• Your Core Web Vital metrics will be affected like Largest Contentful Paint (LCP)

Solution:

• Use the ‘loading = “lazy”’ attribute for images in your HTML files
• Alternatively, enable lazy loading plugins like Smush for WordPress

Overlooking Mobile Optimisation

Many websites still focus on desktop users even though a majority of people access sites through their mobile.

Google also prioritises mobile for indexing first which means your site may be ranking poorly if your images aren’t optimised for mobile. 

Why It’s a Problem:

• Mobile users may experience slow loading or improperly scaled images
• Google prioritises mobile-friendly sites

Solution:

• Implement responsive design with the <picture> element or ‘srcset’ attribute in your HTML files
• Use a website builder or host that takes care of web responsiveness for you

Conclusion

You may be able to see why image optimisation is essential for success in 2025 now.

Websites today have to meet many expectations such as speed, quality and usability. 

Not only to keep users engaged and coming back, but also to keep the various search engines friendly towards your content.

You can keep this relationship between you, your users and search engines growing by adopting the right practices and avoiding common mistakes.

Image optimisation is just one of these practices, but it’s a crucial one. 

Just remember, if you take the time to implement some of the actions outlined in this article then you can expect faster page load times, an improved user experience and better SEO rankings.

It’s also something you’ll want to blow the cobwebs off now and then to ensure your efforts are being rewarded.

In 2025, the rigorous standards all websites have to meet in order to rank at the very top will continue to rise.

Trends like visual search, mobile-first indexing and AI-powered optimisation will continue to gain ground.

Making sure your website is fast, high quality and seamless will put you into a position to rise through the SERP rankings.

Hopefully this guide is something you can come back to again and again to check you’re on the right track for image optimisation.

But don’t forget, you can find even more SEO guides on our website to add more strings to your SEO bow.

FAQs About Image Optimisation

1. What is Image Optimisation, and Why is it Important?

Image optimisation is the process of reducing the file size of images without compromising their quality. It involves techniques such as compression, resizing, and selecting the right file format to improve website performance.

Why It’s Important:

• Faster page load times enhance user experience and reduce bounce rates.
• Optimised images improve SEO rankings, as search engines prioritize fast-loading websites.
• Lower hosting and bandwidth costs for image-heavy websites.

2. What Are the Best Tools for Image Optimisation?

There are many tools available to simplify the image optimisation process, including:

• Squoosh: Great for compressing images manually.
• TinyPNG: Ideal for batch compression of PNG and JPEG files.
• ShortPixel: A WordPress plugin for bulk optimisation.
• Cloudinary: A powerful platform for advanced and automated image delivery.
• EWWW Image Optimizer: Automates image optimisation for WordPress users.

3. What is the Difference Between Lossy and Lossless Compression?

• Lossy Compression:
• Reduces file size by permanently discarding some image data.
• Ideal for photos and blog images where small file size matters more than perfect quality.
• Example: JPEG.
• Lossless Compression:
• Reduces file size without losing any image data.
• Best for logos, graphics, and images that require high fidelity.
• Example: PNG, WebP.

4. How Can I Optimise Images Without Losing Quality?

To retain quality while reducing file size:

1. Choose lossless compression for sensitive images like logos and graphics.
2. Use next-generation formats like WebP or AVIF.
3. Resize images to match their required dimensions before uploading.
4. Strip unnecessary metadata using tools like ImageOptim.

5. What File Format Should I Use for My Images?

The best format depends on the image’s purpose:

• JPEG: Best for photographs and high-resolution images where file size matters.
• PNG: Ideal for logos, icons, and transparent images.
• WebP/AVIF: Excellent for websites needing high-quality images with small file sizes.
• GIF: Suitable for simple animations but not recommended for static images.
• SVG: Perfect for scalable graphics like logos and icons.

6. What is Alt Text, and Why Does it Matter?

Alt text (alternative text) is a written description added to an image’s HTML tag, helping search engines and screen readers understand the image content.

Why It’s Important:

• Improves accessibility for users with visual impairments.
• Boosts on-page SEO by providing context to search engines.
• Helps images rank in Google Image Search.

Tips for Writing Alt Text:

• Be concise and descriptive.
• Use relevant keywords, but avoid keyword stuffing.
• Keep it accurate and within the context of the page.

7. What is Lazy Loading, and How Does It Improve Website Speed?

Lazy loading is a technique that delays the loading of images until they are needed, such as when they become visible in the user’s viewport.

Why It’s Important:

• Reduces initial page load times, especially for image-heavy pages.
• Improves Core Web Vitals metrics like Largest Contentful Paint (LCP).

How to Implement:

• Add the loading=”lazy” attribute to image tags.
• Use plugins like Smush for WordPress to enable lazy loading automatically.

8. How Do I Monitor Image Performance on My Website?

Monitoring image performance ensures that your optimisation efforts are effective and identifies areas for improvement.

Best Tools:

• Google PageSpeed Insights: Analyzes loading speed and suggests improvements.
• Lighthouse: Provides detailed insights into image performance and Core Web Vitals.
• Google Analytics: Tracks engagement metrics, such as bounce rates and time on page.

9. How Often Should I Optimise My Website’s Images?

Image optimisation isn’t a one-time task. It should be an ongoing process.

When to Optimise:

• During website updates or redesigns.
• When adding new content, such as blog posts or product pages.
• After analyzing performance metrics and identifying bottlenecks.

10. Can Optimised Images Help with Visual Search?

Yes! Visual search tools like Google Lens and Pinterest rely heavily on well-optimised images.

Best Practices for Visual Search:

• Use descriptive filenames and Alt text to help search engines understand your images.
• Include structured data to make your images more discoverable.
• Ensure your images are clear, high-quality, and mobile-friendly.