WebP: When It's Worth It, and When It Isn't

WebP does something genuinely useful: it produces noticeably smaller files than JPG or PNG at comparable quality, and unlike JPG it can store transparency. If you run a website, that is a real bandwidth saving for free.

It is also the format that makes people download a converter, because plenty of software still will not open it.

What it actually gives you

One format covering both jobs. JPG is good at photographs and cannot do transparency at all. PNG does transparency and lossless quality but produces large files for photographic content. WebP does both, and does each of them smaller.

For anything served over the web, that is the right trade. Every current browser supports it.

Where it stops being the right answer

Browser support is universal. Support everywhere else is patchy, and that gap is the whole reason the conversion tools exist.

Older desktop software, plenty of print workflows, some image editors, various upload forms, and a good deal of corporate software will reject a .webp outright or show you nothing. If the destination is not a browser, WebP is a gamble.

That is when you convert out of it:

• WebP to JPG for photographs headed anywhere that might be fussy. JPG is the most universally readable image format there is.
• WebP to PNG when the image has transparency you need to keep, or when it is a graphic rather than a photo.

Converting into WebP: the part worth understanding

Going the other direction, the source format decides how much the conversion costs you - and the two conversions are not equivalent.

PNG to WebP takes a lossless source. Every original pixel is still there, so this is the first time the image is compressed with loss. On photographs it is very hard to see. On screenshots, UI captures, text and line art it is more visible, because a lossy encoder spends its bits on photographic detail rather than hard edges. Transparency survives - WebP keeps the alpha channel.

JPG to WebP takes a source that has already been through lossy compression once. This is a second generation, not a first. It cannot recover what the original JPG discarded, and it can add its own artefacts on top, usually around the high-contrast edges the first pass had already softened. And since JPG has no alpha channel, there is no transparency to preserve.

Neither is a reason to avoid converting. Converting once is fine. What visibly degrades an image is round-tripping repeatedly between lossy formats - so keep the file you started from rather than re-converting the output later.

The decision, briefly

• Serving images on your own site? WebP. The saving is real and browsers handle it.
• Sending a file to another person or another system? JPG if it is a photo, PNG if it needs transparency or has sharp edges. Compatibility beats file size the moment you lose control of what opens it.
• Archiving originals? Keep whatever you shot or exported. Do not convert an archive to save space - that is what the trade costs you and you cannot undo it.
• Screenshots, logos, line art? Stay on PNG unless size genuinely matters. The edges are exactly what lossy compression handles worst.

If size is the actual problem

Worth separating two different goals, because people reach for a format conversion when they wanted compression.

If your file is simply too big for an upload limit, changing format is an indirect fix. Compress Image re-encodes at a lower quality and keeps the format, which is usually what you meant. It offers three real quality levels rather than vague labels, and shows the estimated output size before you commit.

If the image is also the wrong dimensions - a 12-megapixel phone photo going into a 400-pixel avatar slot - Resize Image will do far more for the file size than any format change. Resizing then compressing beats converting almost every time.

The short version

WebP is the right format for images you serve and the wrong one for images you send. Convert into it for your own site, convert out of it when something refuses to open the file, and remember that a JPG source starts from further behind than a PNG one.

Images are capped at 20 MB and 8000 by 8000 pixels, and everything is deleted from our servers an hour later.