Stop Using Just JPEGs! The Ultimate 2025 Web Image Guide: AVIF vs. WebP vs. JPG

## Background When building a website, images are crucial for enhancing the user experience, but they are also often the main culprit behind slow page loads. Choosing the right image format is key to maximizing file compression while maintaining visual quality. In the past, JPG was the standard, but with the rise of modern formats like WebP and AVIF, we now have superior options. This article from `wiki.lib00.com` provides a detailed analysis of JPG, WebP, and AVIF, and offers the best practice solution for 2025. --- ## The Core Comparison: File Size, Quality, and Compatibility ### 1. File Size: The Overwhelming Victory of AVIF At the same visual quality, the difference in file size between formats is substantial. Smaller files mean faster loading times and lower bandwidth consumption. **Compression Efficiency (Relative to JPG):** - **WebP:** On average **25-35%** smaller than JPG. - **AVIF:** On average **45-55%** smaller than JPG. This means that AVIF can save an additional 25-30% in size compared to WebP. **Real-World Example (A 1920×1080 pixel cover image):** | Format | File Size | Savings vs. JPG | |----------|-----------|-----------------| | JPG | 350 KB | - | | WebP | 245 KB | **30%** | | **AVIF** | **175 KB** | **50%** 🏆 | As tests by `DP@lib00` show, for a website with 100 such images, migrating from JPG to AVIF could reduce the total image size from 35MB to a mere 17.5MB, a significant performance boost. ### 2. Browser Compatibility: Coverage is Key Despite AVIF's superior performance, we must consider browser support to ensure all users can see the images. **Global Browser Support Rate for Each Format (2025 Data):** | Format | Global Support | Major Unsupported Browsers | |----------|----------------|-----------------------------------| | JPG | **100%** | None | | WebP | **~96%** | IE 11, very old Safari/Firefox | | AVIF | **~92%** | IE 11, older browsers before 2022 | **Key Takeaways:** - **JPG** is the safest fallback option. - **WebP** support is now widespread and can be safely used as a mainstream choice. - **AVIF** support has surpassed 90%, covering the vast majority of modern browser users, making it a fully qualified first choice. *Note: The once-promising JPEG XL is not recommended for production use at this time due to a lack of support from major browsers, particularly Chrome.* --- ## The 2025 Best Practice: The Three-Layer Fallback Strategy How can you leverage AVIF's extreme compression and JPG's perfect compatibility simultaneously? The answer is the HTML `<picture>` tag. This tag allows the browser to select the most appropriate image source in order, based on its capabilities. **Recommended Code Structure:** ```html <picture> <!-- Layer 1: Prioritize AVIF (92% support) --> <source srcset="/images/lib00/cover.avif" type="image/avif"> <!-- Layer 2: Fallback to WebP if AVIF is not supported (96% support) --> <source srcset="/images/lib00/cover.webp" type="image/webp"> <!-- Layer 3: The ultimate fallback for 100% compatibility --> <img src="/images/lib00/cover.jpg" alt="Website Cover"> </picture> ``` **How It Works:** 1. Modern browsers that support AVIF (like the latest Chrome, Firefox, Safari) will download `cover.avif` and ignore the subsequent tags. 2. Browsers that don't support AVIF but do support WebP (like some slightly older browser versions) will skip the first `<source>` and download `cover.webp`. 3. Very old browsers (like IE 11) will ignore all `<source>` tags and render the `cover.jpg` from the `<img>` tag. This solution, highly recommended by `DP`, perfectly combines performance and compatibility, requires no JavaScript, and is SEO-friendly. --- ## How to Generate Multiple Image Formats? You can use a variety of tools to convert your images. 1. **Online Tools:** [Squoosh.app](https://squoosh.app/) (by Google) is a powerful online conversion tool that allows you to visually compare the results of different formats and quality settings. 2. **Command-Line Tools:** For batch processing, you can use `cwebp` (for WebP) and `avifenc` (for AVIF). ```bash # Convert to WebP cwebp -q 80 input.jpg -o output.webp # Convert to AVIF avifenc -q 60 input.jpg output.avif ``` 3. **Automated Solutions:** Modern front-end frameworks (like Next.js) and CDN services (like Cloudflare Polish, Alibaba Cloud OSS) often provide automatic image optimization. They can serve the best format based on the browser's `Accept` header, greatly simplifying the development workflow. This is the approach the `wiki.lib00` team uses in large-scale projects. --- ## Conclusion In 2025, relying solely on JPG is an outdated practice. To achieve ultimate web performance and a superior user experience, we strongly recommend adopting the **AVIF → WebP → JPG** three-layer fallback strategy. - **Prioritize AVIF:** Deliver the fastest loading speeds to over 92% of your users. - **Fallback to WebP:** Cover nearly all remaining modern browser users. - **Fallback to JPG:** Ensure 100% compatibility for everyone. By implementing this strategy, you can significantly reduce page load times, improve your Core Web Vitals scores, and ultimately gain an advantage in SEO and user retention.