A picture is worth more than a thousand words. Images are integral to a visually engaging website, whether showcasing products, promoting destinations, or crafting banners.
However, unoptimized images can be a significant roadblock for high-performing websites. Since images contribute over 60% of a page’s weight, unoptimized images can drag downloading speeds, increase bounce rates, hurt SEO rankings, and affect user experience (UX). For WordPress site managers and developers, image optimization isn’t an option – it’s a must.
Fortunately, image optimization is not a complex task. In this guide, we’ll examine why image optimization is critical, how to convert and compress images old-age image formats such as PNG and JPEG to WebP and AVIf effectively, and leverage plugins and best practices for effective image optimization.
Table of Contents
Importance of Image Optimization for WordPress Performance
Website visitors are impatient. According to the Forbes Advisor survey, people will wait an average of eight seconds for a website to load in 2024. If your web pages load too slowly or are unresponsive, you risk frustrating searchers, impacting your rankings, and potentially losing traffic to competitors. Every second matters—and Google has been telling this since 2010—to load a website within 2 seconds.
How Images Impact Website Speed
According to the HTTP org study on page weight, images are the most significant contributor to webpage size, 1,026 KB for desktop and 811 KB for mobile. That’s more than HTML (31 KB), CSS (72 KB), and JavaScript (509KB) combined.
Images are typically one of the biggest and often overlooked performance issues for slow websites. While high-resolution pictures, photo widgets, and image sliders look great, if they are unoptimized, they can impact your loading time and harm your Largest Contentful Paint (LCP) score, one of the Core Web Vitals metrics.
What Is Image Optimization?
Image optimization compresses and delivers images in the smallest possible file size without reducing overall image quality. Effectively optimized images can be up to 80% smaller than the original without losing quality. This can be achieved through image compression, that maybe either ‘lossy’ or ‘lossless.’ Lossless compression reduces the overall file size without impacting image quality. In lossy compression, there may be a minor loss in quality, but won’t be noticeable to website visitors.
Given the significant performance impact of images, choosing the right format becomes critical. Vector formats are ideally suited for images with less complex geometric shapes, such as logos, text, or icons, but they are unsuitable for picture images. Traditional raster formats like PNG and JPEG are widely supported but lack the efficiency of modern formats like WebP and AVIF.
Benefits of Image Optimization
Improved Page Speed: Smaller images reduce file transfer time, allowing pages to load faster.
Better SEO Rankings: Faster loading helps improve your site visibility in search results as page speed directly impacts SEO.
Enhanced User Experience: Quick-loading and responsive visuals improve engagement.
Reduced bandwidth costs: Smaller image sizes consume less data, helps users and servers.
Lower Storage Needs: Optimized images take up less server space, making backups faster and cost-effective.
| Format | Transparency | Animation | Compression Efficiency | Browser Support | |
| PNG | Yes | Limited | Low | Universal | |
| JPEG | No | No | Moderate | Universal | |
| WebP | Yes | Yes | High | Modern Browsers | |
| AVIF | Yes | Yes | Very High | Growing (93%+ browsers) |
Understanding Modern Image Formats: AVIF, WebP, and More
Traditional image formats, PNG and JPEG, have long been the backbone of web imagery, but they fall short in balancing quality and size. Modern image formats such as AVIF and WebP are designed to overcome these limitations, offering better compression, faster loading times, and advanced features.
What Is AVIF?
AVIF (AV1 Image File Format) is an open-source image compression format developed by the Alliance for Open Media (AOMedia). Based on the AV1 video codec, AVIF leverages advanced compression techniques, such as chroma subsampling and adaptive quantization, to deliver high-quality visuals at a fraction of the size of traditional image formats.
Advantages:
Superior compression efficiency: AVIF images are often 50% smaller than comparable JPEG files.
High-quality images: supports high-quality imaging, including HDR, wide color gamut, and transparency.
Cost-effective: AVIFs are royalty-free, making them accessible and cost-effective for developers, and content creators.
Wide compatibility and support: AVIF is supported by modern web browsers, image editing tools and CDNs.
Limitations:
Decoding is slightly slower on older devices and has limited browser support. It is also less effective in compressing non-photographic images compared to PNG or lossless WebP.
What Is WebP?
WebP, developed by Google, is a next-generation image format that provides better lossless and lossy compression than traditional formats like JPEG, PNG, and GIF. WebP images can be up to 35% smaller in size compared to JPEG images while maintaining similar visual quality.
Advantages of WebP
Broad Compatibility: Supported by modern browsers
Improved UX: Maintains high image quality while minimizing load times.
Flexibility: Ideal for a variety of content types, from e-commerce product images to blog illustrations.
Limitations of WebP
Less advanced than AVIF for preserving intricate details in high-fidelity images.
Older Browser Compatibility: Requires fallback mechanisms for legacy browsers.
How to Convert and Compress Images for Faster WordPress Sites
There are multiple ways to optimize images, such as resizing, compressing, and choosing the proper image format.
How to Use AVIF on WordPress Sites
Starting with WordPress version 6.5, you can use AVIF images directly into your website, similar to a JPEG or PNG images.
Verify Hosting Support
Ensure your hosting provider supports AVIF, as this facility is unavailable with all hosting providers. Without hosting support, AVIF files may not display correctly on your site. Alternatively, you may need to configure server settings manually or switch to a modern hosting platform like InstaWP Live, which provides built-in support for AVIF and WebP. InstaWP Live’s infrastructure includes updated PHP versions and essential libraries like libavif and libwebp. This ensures compatibility and efficient processing of AVIF and WebP images.
Install an AVIF-Compatible Plugin
Use WordPress plugins like ShortPixel or Optimole to automatically convert uploaded images into AVIF format and serve them efficiently.
Test Compatibility
Use a staging environment such as InstaWP sandbox’s portable WordPress staging environment for testing. To test AVIF image compatibility with themes, plugins, or browsers. Confirm images display correctly across devices before deploying changes. With InstaWP, development teams can quickly launch WordPress sandbox environments, making it easier to test various scenarios before moving to the production stage.
Converting Images to WebP for WordPress
Convert Your Images to WebP Format: You should convert images into WebP before uploading them to your WordPress website. You can use plugins and free to convert the images. `
Upload WebP Images: Once you have WebP images, go to your WordPress dashboard > Media > Add New and upload them. You can also drag and drop them directly into the library and insert them into your posts and pages.
Testing and Compatibility: Once you have made the changes and published, open the website content on different browsers and devices to confirm that WebP images are displayed properly.
Tools to Convert and Compress Images for WordPress
If you already have existing images on your website in other formats, you can convert them to WebP using various tools and plugins.
1. ShortPixel Image Optimizer
ShortPixel supports AVIF and WebP conversions while offering powerful compression options. It provides bulk optimization for existing media libraries and automatically converts uploaded images into AVIF or WebP formats.
2. Imagify
Imagify simplifies image optimization with its intuitive interface and automatic compression. It converts and compresses images to WebP format automatically without noticeable quality loss.
Source: Imagify
3. Optimole
Optimole combines image optimization with CDN integration. It supports AVIF and WebP delivery and automatically resizes and compresses images based on user devices.
4. Smush Pro
Smush Pro provides lazy loading and bulk compression without reducing visual quality.
5. EWWW Image Optimizer
EWWW Image Optimizer excels at server-side image compression and supports modern formats. It provides bulk optimization of media library and theme images.
6. Squoosh.app (Online Tool)
Squoosh is a browser-based tool by Google that offers quick image conversion and compression. It supports multiple formats, including WebP.
7. Kraken.io
Kraken.io is a web-based tool with a dedicated WordPress plugin for easy integration. The tool provides advanced lossy and lossless compression and also supports bulk image optimization.
| Tool | Formats Supported | Compression Type | Integration | Best For |
| ShortPixel | AVIF, WebP | Lossy/Lossless | WordPress Plugin | Advanced format support |
| Imagify | WebP | Lossy/Lossless | WordPress Plugin | User-friendly optimization |
| Optimole | AVIF, WebP | Lossy/Lossless | WordPress + CDN | Dynamic delivery via CDN |
| Smush Pro | WebP | Lossy/Lossless | WordPress Plugin | Lazy loading + optimization |
| EWWW Image Optimizer | WebP | Lossy/Lossless | Server-Side Plugin | Large-scale optimization |
| Squoosh.app | WebP | Lossy/Lossless | Online Tool | Quick manual compression |
| Kraken.io | PNG, JPEG, WebP | Lossy/Lossless | WordPress Plugin | Advanced compression features |
Making Sense of Image Optimization Results
After implementing image optimization, it’s essential to evaluate its impact and make adjustments to ensure optimal performance. Here’s a step-by-step approach:
Analyze Site Performance: You can start by creating a performance baseline to identify the effectiveness and benefits of image optimization efforts. Tools such as GTMetrix, Google Page Speed Insights, or Pingdom help you measure site performance and how much impact is coming from images. Use tools like SEMrush, Ahrefs, or Screaming Frog for SEO audit to find all images stored on your websites, including their size and format.
Run A/B tests using tools such as Google Optimize to create variations of pages with and without optimized images and measure key metrics such as page load times, bounce rates, and conversion rates.
Key Metrics to Monitor:
LCP: Check how quickly the largest visible content (often images) loads.
Total Page Weight: Find out how much of the total page size is occupied by images.
Load Time: Ensure optimized images are contributing to faster page loading speeds.
Step 2: Run Tests on Staging Environments
Before deploying changes to prod, test image optimizations in a staging environment like InstaWP’s sandbox to simulate real-world conditions.
Test images across multiple devices and browsers to ensure compatibility, especially for AVIF and WebP formats.
Check fallback mechanisms by disabling modern formats in one browser and verifying that PNG/JPEG images display properly.
Step 3: Tweak Image Settings for Optimal Performance
Compression Levels: Adjust lossy or lossless compression to balance quality and file size ratio.
Responsive Images: Check if you use <srcset> and <sizes> attributes to serve responsive images for different screen sizes.
CDN Integration: Verify that your Content Delivery Network (e.g., Cloudflare) serves optimized images efficiently.
Best Practices for Compressing and Converting Images in WordPress
Choose the Right Format: Use AVIF for cutting-edge compression and WebP for universal compatibility. PNG: Reserve for images needing transparency but no animation, like logos or icons. JPEG: Use for simpler visuals where compression efficiency isn’t a top priority.
Compress Without Quality Loss: Aim for visual fidelity using tools like Imagify.
Implement Lazy Loading: Images should be loaded when they enter the users’ viewport, reducing initial page load time. You should prioritize above-the-fold images in the initial page load and defer non-critical images using lazy loading.
Enable Responsive Images: WordPress automatically makes images responsive when uploaded in the media library by generating the image markup that includes srcset and size attributes. However, it is good to check if they have been disabled. You can do this by clicking a page, right-clicking, and choosing inspect to check whether the srcset and size attributes are available for all images.
Regularly Update Your Tools. Keep your image optimization tools and plugins that support image formatting periodically updated to provide better compression algorithms and more efficient image handling.
Optimize CSS background images: Implement multiple background-image declarations in your CSS while using WebP for CSS background images.
Conclusion
Optimizing images is essential for WordPress performance, and modern formats like AVIF and WebP are game changers. By leveraging tools, plugins, and hosting solutions like InstaWP Live, you can deliver faster, smoother experiences for your audience. Start optimizing today to unlock your WordPress site’s full potential.
FAQs
What is the benefit of AVIF over WebP?
AVIF offers superior compression and quality but has limited browser support compared to WebP.
How do I automate image optimization in WordPress?
Use plugins like ShortPixel or Imagify for automated compression and format conversion.
Does InstaWP support AVIF and WebP?
Yes, InstaWP Live is fully optimized for these modern image formats.
Can I bulk-compress images in WordPress?
Tools like EWWW Image Optimizer and Smush Pro support bulk image compression.
Do I need advanced hosting for AVIF/WebP?
Hosting optimized for modern formats (like InstaWP Live) simplifies implementation.
How do I optimize images in WordPress without plugins?
Use Online image compression tools to compress your image to the desired size and resolution while maintaining the quality as much as possible.