WebP has no progressive mode: converting progressive JPEGs to WebP loses the blurry-to-sharp first paint
Google's WebP FAQ: WebP does not offer progressive or interlaced decoding refresh in the JPEG or PNG sense. A large hero image that used to appear early as a low-quality preview now appears only as it decodes.
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Why it matters
- A progressive JPEG paints a coarse full frame early, then refines it. Converting to WebP makes the file smaller but changes how the image arrives.
- For large above-the-fold images on slow connections, the smaller WebP can still feel slower.
Options
- Keep progressive JPEG for the few large hero images, and use WebP or AVIF elsewhere.
- Or show a tiny inline placeholder (a blurred thumbnail, or a dominant-color background) while the WebP loads.
- Measure on a throttled connection rather than by file size alone.
Conditions
- observed_via
- documentation
- observed
- 2026-10-01
Sources
- WebP FAQ — Does WebP support progressive or interlaced display? WebP does not offer a progressive or interlaced decoding refresh in the JPEG or PNG sense.