Conversion from an Already Compressed Format: If the original image was already in a compressed format like JPEG, and it was highly compressed, converting it to WebP without allowing for some quality loss can result in a larger file.

Simpliar images: If images that are more graphic with fewer colors and simple shapes often compress better in WebP, sometimes even better than other formats like PNG or GIF, which are also known for handling such images well. This can lead to significant savings in file size with WebP for these simpler images.

Smaller File Sizes: WebP images are typically 25-34% smaller in file size compared to JPEGs and PNGs while retaining the same quality, leading to faster page load times.

Improved Performance: Smaller image file sizes result in quicker downloads and reduced bandwidth usage, which can improve the overall performance of your website, particularly on mobile devices with slower internet connections.

Enhanced User Experience: Faster page loads contribute to a smoother and more enjoyable user experience, potentially reducing bounce rates and increasing time on site.

Transparency Support: Like PNG, WebP also supports transparency (alpha channel), allowing for the creation of images with transparent backgrounds that can be used over various backgrounds on a website.

Animation Support: WebP can be used for animations as an alternative to the GIF format, providing better compression and quality.

SEO Benefits: Improved page load times and site performance can positively impact search engine rankings, as speed is a ranking factor for search engines like Google.

Reduced Server Load: Smaller file sizes mean that your server will have to deal with less data transfer, which could reduce hosting bandwidth requirements and costs.

Future-Proofing: As internet standards evolve and the adoption of WebP grows, using the format may help future-proof your website for upcoming technological advancements and standards.