Progressive JPEG
A JPEG encoding method that renders the entire image in progressively sharper passes, allowing users to see a low-resolution preview before full loading completes.
Progressive JPEG encodes image data in multiple scans (passes). Unlike baseline JPEG which renders top-to-bottom line by line, progressive mode displays a blurry preview of the entire image first, sharpening with each subsequent scan.
On slow connections or mobile networks, users perceive faster loading since the overall composition is visible early. File sizes are comparable to baseline JPEG, often slightly smaller for images over 10 KB. However, decoding requires holding the entire image in memory, increasing memory consumption.
The image compression tool offers progressive output options as part of image optimization workflows. Google's PageSpeed Insights recommends progressive JPEG for improved perceived performance.