Boost performance and user experience with these image optimization tips for your web apps. Sergio Vergara Sergio Verga
Posted: Sat Jan 25, 2025 10:49 am
Boost performance and user experience with these image optimization tips for your web apps.
Sergio Vergara
Sergio Vergara
December 12, 2023 — 7 minutes reading time
10 Image Optimization Tricks for a Perfect Web Experience
Photo by Alexander Dummer on Unsplash
We will explain effective image optimization techniques effective ireland mobile numbers list that significantly improve your website's performance.
1. Image formats
Choosing the right image format for each type of image can significantly impact the size and quality of the image file. Here is the list of different image formats that you can use for your website.
a. WebP
WebP is an image format developed by Google that offers better compression and smaller file sizes compared to JPEG and PNG. It is supported by most modern browsers (except some versions of Safari and Internet Explorer). To use WebP, you can provide WebP formats and alternative formats such as JPEG or PNG in your HTML.
webP compatibility is:
b. JPG 2000
JPEG 2000 is another high-quality image format with good compression. However, its browser support is limited. Similar to WebP, you can provide a JPEG 2000 version and alternative formats.
JPG 2000 compatibility is:
C. AVIF
AVIF is a newer image format that provides excellent image compression and quality. It is supported by modern browsers such as Chrome and Firefox.
AVIF compatibility is:
While WebP and AVIF are supported by modern browsers, JPEG 2000 has limited support. Therefore, it is essential to test your website or application in different browsers to ensure proper image display for all users.
2. Responsive images
Responsive images allow you to display different images depending on the user's device and screen size. This prevents large images from loading on smaller screens, saving bandwidth. Use the srcset and sizes attributes on the img element to achieve this:
sizes : Informs the browser of the intended display size of the image based on the size. It does not affect which image the browser chooses to download. srcset : Lists multiple image sources with width descriptors (800w). Each width descriptor represents the actual width of the image in pixels. When the browser encounters both attributes ( sizes and srcset ), it follows these steps:
Evaluates the sizes attribute to determine the desired display size of the image based on the width of the device's viewport.
It then uses this calculated size, along with the width descriptors available in srcset , to decide which image to download. The browser selects the image with the closest width descriptor (closest to the calculated size) from srcset .
3. Lazy loading
Lazy loading is a method that postpones the loading of images until they are about to become visible in the user's viewport. This reduces the initial page load time. It uses the loading="lazy" attribute on the img element (by default, the loading attribute is set to eager)
4. Preloading and caching
Preload critical images to reduce lag when they are really needed. Use the link tag with rel="preload" in the head of your HTML:
Also, consider using service workers to cache images for later visits. The following is a basic example of using a service worker to cache images.
In a React app, you can use the react-helmet package to add the preload link in the HTML head section for critical images.
5. Image Sprites
A sprite sheet is a single image that contains multiple smaller images or icons. It is used to reduce the number of HTTP requests when rendering numerous small images on a web page. By loading a single sprite sheet, you can display specific images by adjusting the position with CSS.
Let's say you're building a social media web app and you want to display various icons for actions like liking a post, commenting, and sharing. Each icon is a small image that is typically used in different parts of the app.
Without Image Sprites:
In a traditional approach, you would include each icon as a separate image file in your HTML or CSS, like this:
With Image Sprites:
By using image sprites, you can combine all of these icons into a single sprite sheet, reducing the number of HTTP requests. Here's an example of what that might look like:
In this example, all icons (like, comment, share, etc.) are combined into a single icons-sprite.png sprite sheet. The CSS classes (e.g. .like-icon, .comment-icon, .share-icon) use the background-position property to display the correct part of the sprite sheet as the background for each icon.
You can do the same with the help of tools like https://icomoon.io/ that will help you generate the sprite sheet and CSS with the name of the classes you configure.
Benefits:
Instead of loading multiple image files, the web app now loads only one image (icons-sprite.png), which reduces the number of HTTP requests.
The sprite sheet is loaded once and can be cached by the browser, which improves subsequent page loads.
CSS classes control the display of individual icons in the sprite sheet, allowing for fluid hover and scrolling effects without additional loading delays.
This leads to faster, more efficient user experiences with improved loading times.
6. Responsive Image Service
Adaptive Image Serving is a technique used in web development to deliver images optimized for the user's specific device and network conditions. Adaptive Image Serving aims to provide the best possible image quality while minimizing image file size and ensuring optimal performance.
Typically, this service is managed by a CDN or an image server with dynamic resizing capabilities, and implementation details may vary depending on the service you choose. For example, if you prefer to use AWS CloudFront, check out this link for more information on image optimization: AWS Blog: Image Optimization with Amazon CloudFront and AWS Lambda .
7. Remove metadata
Removing metadata from images is an essential step in image optimization. Because image metadata can sometimes take up a significant portion of an image's file size, especially for images captured with digital cameras or phones, by removing the metadata, you can significantly reduce the overall file size of the image, leading to faster loading of the image on web pages. Tools like ImageMagick or other online tools allow you to remove image metadata.
8. Use SVG for icons and logos
SVGs are great for simple icons because they are vector-based and can be scaled without losing quality.
Using SVG for icons provides a lightweight, scalable, and visually appealing solution that improves web page performance, ensures crisp images, and enhances the overall user experience across multiple devices and browsers.
Using SVG can also be useful for logos, but be careful, as a marketing strategy it may be better to use a standard format so that users can download the logo and view and use it without format problems.
9. Image dimensions
Specifying image dimensions in HTML or CSS is essential to avoid layout shifts and improve page rendering speed. By specifying image dimensions in HTML or CSS, you provide the browser with the information needed to allocate the correct space for the image during the initial rendering process.
Benefits
Avoid layout shifts: Specifying dimensions ensures that the browser knows the exact size of the image before loading it, avoiding sudden layout shifts.
Faster page rendering: With the image dimensions known in advance, the browser can render the layout more efficiently, speeding up page load times.
Improved user experience: By eliminating layout shifts, users have a more consistent and enjoyable browsing experience.
To specify the dimensions of the image, you can either include the width and height attributes directly inside the <img> tag or apply a specific style by adding a class attribute to the <img> tag in CSS.
10. Blur
Apart from the techniques mentioned above, you can use Blur techniques like Blurhash which allows automatic image compression with a CDN for faster loading, where the image is initially displayed in low resolution and progressively improves its quality as it loads completely, and progressive loading of images for gradual improvement in quality.
Conclusion
Image optimization is crucial to improving performance and user experience in web applications. Appropriate choice of formats such as WebP and AVIF, implementation of responsive images, lazy loading, use of sprite sheets, responsive image services, removal of metadata, preference for SVG for icons and logos, specification of dimensions, and application of techniques such as Blur are effective strategies to reduce file sizes, speed up loading times, and deliver an improved user experience across various platforms and devices.
Sergio Vergara
Sergio Vergara
December 12, 2023 — 7 minutes reading time
10 Image Optimization Tricks for a Perfect Web Experience
Photo by Alexander Dummer on Unsplash
We will explain effective image optimization techniques effective ireland mobile numbers list that significantly improve your website's performance.
1. Image formats
Choosing the right image format for each type of image can significantly impact the size and quality of the image file. Here is the list of different image formats that you can use for your website.
a. WebP
WebP is an image format developed by Google that offers better compression and smaller file sizes compared to JPEG and PNG. It is supported by most modern browsers (except some versions of Safari and Internet Explorer). To use WebP, you can provide WebP formats and alternative formats such as JPEG or PNG in your HTML.
webP compatibility is:
b. JPG 2000
JPEG 2000 is another high-quality image format with good compression. However, its browser support is limited. Similar to WebP, you can provide a JPEG 2000 version and alternative formats.
JPG 2000 compatibility is:
C. AVIF
AVIF is a newer image format that provides excellent image compression and quality. It is supported by modern browsers such as Chrome and Firefox.
AVIF compatibility is:
While WebP and AVIF are supported by modern browsers, JPEG 2000 has limited support. Therefore, it is essential to test your website or application in different browsers to ensure proper image display for all users.
2. Responsive images
Responsive images allow you to display different images depending on the user's device and screen size. This prevents large images from loading on smaller screens, saving bandwidth. Use the srcset and sizes attributes on the img element to achieve this:
sizes : Informs the browser of the intended display size of the image based on the size. It does not affect which image the browser chooses to download. srcset : Lists multiple image sources with width descriptors (800w). Each width descriptor represents the actual width of the image in pixels. When the browser encounters both attributes ( sizes and srcset ), it follows these steps:
Evaluates the sizes attribute to determine the desired display size of the image based on the width of the device's viewport.
It then uses this calculated size, along with the width descriptors available in srcset , to decide which image to download. The browser selects the image with the closest width descriptor (closest to the calculated size) from srcset .
3. Lazy loading
Lazy loading is a method that postpones the loading of images until they are about to become visible in the user's viewport. This reduces the initial page load time. It uses the loading="lazy" attribute on the img element (by default, the loading attribute is set to eager)
4. Preloading and caching
Preload critical images to reduce lag when they are really needed. Use the link tag with rel="preload" in the head of your HTML:
Also, consider using service workers to cache images for later visits. The following is a basic example of using a service worker to cache images.
In a React app, you can use the react-helmet package to add the preload link in the HTML head section for critical images.
5. Image Sprites
A sprite sheet is a single image that contains multiple smaller images or icons. It is used to reduce the number of HTTP requests when rendering numerous small images on a web page. By loading a single sprite sheet, you can display specific images by adjusting the position with CSS.
Let's say you're building a social media web app and you want to display various icons for actions like liking a post, commenting, and sharing. Each icon is a small image that is typically used in different parts of the app.
Without Image Sprites:
In a traditional approach, you would include each icon as a separate image file in your HTML or CSS, like this:
With Image Sprites:
By using image sprites, you can combine all of these icons into a single sprite sheet, reducing the number of HTTP requests. Here's an example of what that might look like:
In this example, all icons (like, comment, share, etc.) are combined into a single icons-sprite.png sprite sheet. The CSS classes (e.g. .like-icon, .comment-icon, .share-icon) use the background-position property to display the correct part of the sprite sheet as the background for each icon.
You can do the same with the help of tools like https://icomoon.io/ that will help you generate the sprite sheet and CSS with the name of the classes you configure.
Benefits:
Instead of loading multiple image files, the web app now loads only one image (icons-sprite.png), which reduces the number of HTTP requests.
The sprite sheet is loaded once and can be cached by the browser, which improves subsequent page loads.
CSS classes control the display of individual icons in the sprite sheet, allowing for fluid hover and scrolling effects without additional loading delays.
This leads to faster, more efficient user experiences with improved loading times.
6. Responsive Image Service
Adaptive Image Serving is a technique used in web development to deliver images optimized for the user's specific device and network conditions. Adaptive Image Serving aims to provide the best possible image quality while minimizing image file size and ensuring optimal performance.
Typically, this service is managed by a CDN or an image server with dynamic resizing capabilities, and implementation details may vary depending on the service you choose. For example, if you prefer to use AWS CloudFront, check out this link for more information on image optimization: AWS Blog: Image Optimization with Amazon CloudFront and AWS Lambda .
7. Remove metadata
Removing metadata from images is an essential step in image optimization. Because image metadata can sometimes take up a significant portion of an image's file size, especially for images captured with digital cameras or phones, by removing the metadata, you can significantly reduce the overall file size of the image, leading to faster loading of the image on web pages. Tools like ImageMagick or other online tools allow you to remove image metadata.
8. Use SVG for icons and logos
SVGs are great for simple icons because they are vector-based and can be scaled without losing quality.
Using SVG for icons provides a lightweight, scalable, and visually appealing solution that improves web page performance, ensures crisp images, and enhances the overall user experience across multiple devices and browsers.
Using SVG can also be useful for logos, but be careful, as a marketing strategy it may be better to use a standard format so that users can download the logo and view and use it without format problems.
9. Image dimensions
Specifying image dimensions in HTML or CSS is essential to avoid layout shifts and improve page rendering speed. By specifying image dimensions in HTML or CSS, you provide the browser with the information needed to allocate the correct space for the image during the initial rendering process.
Benefits
Avoid layout shifts: Specifying dimensions ensures that the browser knows the exact size of the image before loading it, avoiding sudden layout shifts.
Faster page rendering: With the image dimensions known in advance, the browser can render the layout more efficiently, speeding up page load times.
Improved user experience: By eliminating layout shifts, users have a more consistent and enjoyable browsing experience.
To specify the dimensions of the image, you can either include the width and height attributes directly inside the <img> tag or apply a specific style by adding a class attribute to the <img> tag in CSS.
10. Blur
Apart from the techniques mentioned above, you can use Blur techniques like Blurhash which allows automatic image compression with a CDN for faster loading, where the image is initially displayed in low resolution and progressively improves its quality as it loads completely, and progressive loading of images for gradual improvement in quality.
Conclusion
Image optimization is crucial to improving performance and user experience in web applications. Appropriate choice of formats such as WebP and AVIF, implementation of responsive images, lazy loading, use of sprite sheets, responsive image services, removal of metadata, preference for SVG for icons and logos, specification of dimensions, and application of techniques such as Blur are effective strategies to reduce file sizes, speed up loading times, and deliver an improved user experience across various platforms and devices.