WebP is a modern image format developed by Google that produces smaller files than JPG and PNG at equivalent visual quality. For websites, where images are typically the largest assets on a page, switching to WebP is one of the most straightforward improvements available — smaller files load faster, which improves user experience and contributes to better Core Web Vitals scores.
This guide covers what WebP offers, where it fits well, where it doesn't, and how to use it practically.
What WebP actually does
WebP uses more sophisticated compression algorithms than JPG, achieving roughly 25–35% smaller file sizes at comparable visual quality for photographs. It supports both lossy and lossless compression — lossy for photographs and complex images, lossless for graphics, logos, and images where exact pixel values matter. It also supports transparency, which PNG handles but JPG doesn't, making WebP a single format that covers use cases previously requiring two separate formats.
The compression improvement is real and consistent. A page that loads several large JPGs will load measurably faster with the same images in WebP. For mobile users on slower connections, the difference is more pronounced. Google's PageSpeed Insights and Lighthouse tools specifically flag JPG and PNG images as candidates for WebP conversion when the savings are significant.
SEO and Core Web Vitals
Google's Core Web Vitals include Largest Contentful Paint (LCP), which measures how quickly the largest visible element on a page loads. For most pages, the largest element is an image — typically a hero image or a large content image above the fold. A slower LCP score affects search ranking. Converting large images to WebP directly reduces the time it takes for that element to load, which improves LCP without any other changes to the page.
The relationship between image format and SEO is specific: it's through page speed metrics, not through any direct signal from the format itself. WebP doesn't rank higher because it's WebP — it ranks higher because the page loads faster.
When WebP isn't the right choice
WebP is well-suited for web use but has limitations worth knowing:
Archival and professional editing workflows. WebP is not a good archival format. If you're storing original image files for future editing, use TIFF or a lossless format that's widely supported by professional editing software. Keep originals in a non-lossy format and export to WebP for web publishing.
Images used outside a web context. WebP isn't universally supported in non-browser software. Some email clients, image viewers, and older design tools don't handle WebP natively. For images that will be shared as standalone files, sent by email, or used in contexts where WebP support is uncertain, JPG is the more compatible format.
Legacy browser support. Internet Explorer doesn't support WebP. Very old versions of Safari didn't support it either, though Safari has had full WebP support since version 14. If your analytics show significant traffic from very old browsers, the <picture> element fallback pattern handles this:
<picture>
<source srcset="image.webp" type="image/webp">
<img src="image.jpg" alt="Description of the image">
</picture>Converting to WebP
Portimg's image converter converts JPG, PNG, and other formats to WebP in the browser without any software installation. Upload your image, select WebP as the output, and download. Batch uploads are supported for converting multiple images at once. No account required, files deleted after processing.
For higher-volume or automated workflows, a few options scale better than browser-based tools. WordPress plugins like ShortPixel and EWWW Image Optimizer convert images to WebP automatically on upload. Static site generators like Next.js and Nuxt have built-in image optimisation that handles WebP conversion and serving. CDNs with image optimisation — Cloudflare, Bunny.net — convert and serve WebP automatically based on browser support without changing your upload workflow.
Implementation tips
Add loading="lazy" to image tags below the fold to defer loading until the user scrolls toward them. This reduces initial page load time without affecting images the user sees immediately on arrival.
Resize images to their actual display dimensions before converting. A 4000px-wide image served in an 800px column downloads four times more pixels than the browser uses — resizing first and then converting to WebP compounds the savings from both steps.
Compress after resizing and converting. WebP's default compression settings are reasonable, but if the tool allows quality adjustment, 75–85% quality is generally indistinguishable from higher settings at screen sizes and produces meaningfully smaller files.