Serve Images In Next Gen Formats: How to Fix This Technical SEO Issue

Understanding Next-Gen Image Formats

What are next-gen image formats?

Next-generation image formats represent a significant leap forward from traditional formats like JPEG and PNG. The term "next-gen" refers to modern image file types designed to achieve smaller file sizes while providing advanced visual features, making them ideal for both web performance and design ^[2]. Currently, the two most widely supported next-gen formats are WebP and AVIF.

WebP, developed by Google, is a modern, royalty-free format that supports both lossy and lossless compression, alpha channels, ICC profiles, and animation—all in a single container ^[2]. AVIF (AV1 Image File Format), released in 2019 by the Alliance for Open Media, builds on the advanced AV1 video codec and offers even higher compression efficiency ^[3]. Despite these advanced options being available, 74% of all websites still use JPEGs as their primary image format ^[4].

The WebP format is gaining traction and now appears on approximately 16. 8% of websites globally—a number that's climbing fast as more developers prioritize performance ^[4].

Benefits of using modern image formats

The performance benefits of switching to next-gen formats are substantial. WebP images deliver a file size reduction of roughly 25-35% compared to JPEGs of similar quality ^[2]. AVIF takes this even further, producing files that are approximately 50% smaller than equivalent JPEG images ^[5].

These file size reductions translate directly into faster page loads. Websites with properly optimized images experience up to 25% faster loading times ^[6]. Perhaps more importantly, slow-loading images increase bounce rates by up to 32% and lower conversions ^[1].

On the flip side, websites that load in under 2 seconds enjoy a 15% higher conversion rate ^[6]. Modern compression algorithms can reduce file sizes by 60-80% with minimal or no perceptible quality loss ^[7]. This means you can maintain visual quality while dramatically reducing the data your visitors need to download.

Comparison of AVIF and WebP

When choosing between AVIF and WebP, understanding their respective strengths helps you make an informed decision for your specific use case. AVIF has a clear advantage when it comes to compression. Generally speaking, AVIF images are 50% smaller than JPEG images, while WebP images are 30% smaller than JPEG ^[5]. At equivalent visual quality, AVIF files are typically 20-50% smaller than WebP files ^[8]. This difference becomes critical on pages filled with image-heavy sections, such as portfolios, product galleries, or hero sliders.

AVIF also excels in retaining fine detail and color depth. It supports higher bit depths (up to 10-12 bit color), which means more precise colors and less banding in gradients ^[8]. Additionally, AVIF supports HDR content, while WebP does not ^[3]. However, WebP wins on decoding speed and browser compatibility ^[3]. As of 2025, WebP has 95.

29% browser support compared to 93. 8% for AVIF ^[9]. WebP's faster encoding and decoding can benefit websites with limited server resources or those that need to process images in real-time ^[8]. | Feature | WebP | AVIF | |———|——|——| | Compression vs JPEG | 25-35% smaller | 50% smaller | | Browser Support | 95. 29% | 93.

Implementing Next-Gen Image Formats

Converting existing images to WebP or AVIF

You can convert images using tools like cwebp, avifenc, or GUI tools like Squoosh ^[10]. For those who prefer online solutions, services like Cloudinary offer quick, free, and high-quality conversions with no loss in image clarity ^[11].

For bulk conversions, desktop tools like reaConverter support batch processing, allowing you to convert dozens or even hundreds of files in one go ^[12]. These tools work fully offline and provide fine-tuning options for resolution and quality settings.

When converting your images, keep in mind that WebP performs particularly well for illustrations, icons, and graphics with transparency ^[8]. AVIF is better suited for photography and high-resolution media where you need top-notch quality ^[8].

Automating image conversion with plugins

For WordPress users, automation is straightforward. The Converter for Media plugin automatically converts new images added to the Media Library without modifying your original images ^[13].

By replacing files in standard JPEG, PNG, and GIF formats with WebP and AVIF formats, you can save over half of the page weight without losing quality ^[13]. Images converted to AVIF format weigh about 50% less than images converted only to WebP format, while maintaining better image quality ^[13].

If any visitor has an older browser, these plugins automatically fall back to WebP or the original format. Other popular options include EWWW Image Optimizer and ShortPixel, which offer similar automatic conversion capabilities along with additional optimization features.

Serving next-gen formats with HTML picture element

The HTML “ element is the most reliable way to serve next-gen formats while maintaining compatibility with all browsers. This element acts as a wrapper for an `` tag and optional “ tags ^[14]. Here’s how it works: “`html <source srcset="image.

avif” type=”image/avif”> “` The order of the “ and `` elements is essential as the browser will load the first supported format starting from the top ^[15].

Browsers that support the “ tag start going through tags, choosing the first resource in a format they support. Browsers that don’t support “ tags simply skip them and only see the `` tag ^[14]. This approach ensures you serve AVIF to browsers that support it, WebP as a fallback, and JPEG as the final safety net—maximizing savings without breaking compatibility ^[16].

Optimizing Performance with Next-Gen Formats

Reducing page weight and load times

Images are the most common LCP (Largest Contentful Paint) element, accounting for roughly 80% of all LCP resources ^[17]. This makes image optimization one of the most impactful changes you can make for page speed.

By implementing the AVIF + WebP + JPEG stack, you can achieve 40-50% size reductions and superior visual quality ^[7]. Using modern formats combined with proper compression, you can reduce your image payload by 50-80% ^[18].

Improving Core Web Vitals scores

Core Web Vitals performance is critical for SEO success. Only 47% of websites currently meet Google's thresholds, leading to losses of 8-35% in conversions, rankings, and revenue for businesses that fail to pass ^[17]. The CrUX report confirms positive trends, with 62.

3% of mobile page visits and 74. 4% of desktop visits scoring "good" LCP in July 2025 ^[19]. For the mobile sector, this represents an impressive increase of 46.

6% since 2021 ^[19]. According to 2025 industry research, Core Web Vitals account for approximately 10-15% of ranking signals ^[20]. Case studies demonstrate the impact: – Pinterest saw a 40% decrease in perceived wait time, leading to a 15% SEO traffic increase and 15% sign-up conversion increase ^[17] – Vodafone improved LCP by 31%, resulting in an 8% sales increase ^[17] – The Economic Times improved LCP by 80% to 2.

Balancing image quality and file size

Finding the right balance between quality and file size requires understanding your specific use case. For high-resolution photographs, AVIF delivers superior compression while preserving more texture and color fidelity at smaller file sizes ^[8]. For simpler graphics, icons, and images with text, WebP often performs better.

It supports transparency like PNG but yields a much smaller file size ^[8]. Modern image CDNs can help automate this balance. They process images on the fly by resizing, compressing, and converting formats based on the user's device, screen resolution, and connection speed ^[21].

This dynamic approach allows for considerable reductions in bandwidth usage while maintaining exceptional image quality.

Overcoming Challenges in Next-Gen Format Adoption

Browser compatibility considerations

As of 2025, AVIF has achieved excellent browser support, covering approximately 93-95% of global web users ^[22]. All major browsers—Chrome, Firefox, Safari (from version 16 onward), and Edge—now support AVIF ^[22]. WebP has even broader support at approximately 95.

29% ^[9]. AVIF moved from an experimental curiosity in 2023 to a default capability across Chromium, Firefox, and Safari in 2025 ^[22]. However, edge cases remain.

The primary browser requiring a fallback is Safari on older iOS versions. iPhones running iOS versions older than 2022 (iOS 15. 8) will require a fallback ^[18].

Fallback strategies for older browsers

The best practice in 2025 is clear: use AVIF with a WebP fallback for compatibility ^[16]. This ensures fast-loading images for most users and graceful degradation to slightly larger (but still optimized) images for others. The “ element pattern and content negotiation cover long-tail browsers without extra JavaScript ^[16].

For sites that need maximum compatibility, the recommended approach is: 1. Serve AVIF first 2. WebP as the secondary option 3.

JPEG as the final safety net This strategy maximizes savings without breaking compatibility for any user segment ^[16].

Handling dynamic image content

For sites with user-uploaded images, image CDNs offer powerful solutions. Unlike traditional CDNs that simply cache and deliver original files, image CDNs process images on the fly ^[21].

Solutions like Optimole automatically standardize all uploaded images—fixing dimensions, optimizing compression, and ensuring consistent quality sitewide, regardless of who uploaded the content ^[23]. This eliminates layout shifts, significantly reduces bandwidth usage, and improves Core Web Vitals scores without manual intervention.

Services like Cloudinary and ImageKit analyze each incoming request, the viewer's device capabilities, and the original file content in real-time to serve the lightest possible variant ^[24]. For example, if you deliver a JPEG image, these services might generate and deliver WebP, AVIF, or JPEG XL depending on the requesting browser ^[24].

Measuring the Impact of Next-Gen Image Formats

Using Lighthouse to assess image optimization

Google is preparing to overhaul Lighthouse audits by October 2025 ^[25]. Beginning in June and concluding with the full launch in October 2025, the update will restructure many of Lighthouse's core audits.

Image optimization audits will appear together under "Image Delivery Insight" ^[25]. This consolidation makes it easier to identify and address image-related performance issues in one place.

Lighthouse provides specific recommendations for improving your LCP score, including optimizing images, eliminating render-blocking resources, and improving server response times ^[26]. It tells you not only whether an image is optimized but also how much smaller the optimized version should be ^[26].

Tracking performance improvements with analytics

PageSpeed Insights combines Lighthouse data with real-world Chrome User Experience Report (CrUX) data to give you a holistic view of your site's performance ^[26]. This combination of lab and field data helps you understand both potential improvements and actual user experience. Key metrics to track include: – Largest Contentful Paint (LCP) under 2.

5 seconds – Cumulative Layout Shift (CLS) under 0. 1 – Overall page weight reduction – Image-specific load times Real-world data from CrUX analyzing over 10 million sites demonstrates measurable ROI. Improving LCP from 2.

5s to 1. 5s shows significant business results across multiple case studies ^[17].

A/B testing next-gen formats vs. traditional formats

A/B testing has become essential for businesses looking to optimize conversions and maximize revenue ^[27]. While dedicated image format A/B testing tools are limited, you can measure the impact of format changes through broader performance testing. Primary success metrics include conversion rate, click-through rate, revenue per visitor, and average order value ^[27].

Supporting indicators include time on page, bounce rate, pages per session, and user journey patterns. Research shows that 82% of online users make their watch-or-scroll decision almost instantly—often within two seconds ^[28]. This makes image loading speed particularly critical for user engagement.

When implementing A/B tests, ensure rigorous tracking and thorough QA processes to verify that tracking codes fire correctly, variants render properly across all devices, and conversion goals are captured without error ^[27].