A second round of lossy compression
Most WebP images on the web are lossy, and JPG is always lossy. Converting one to the other therefore means decoding the WebP into pixels and compressing those pixels again with a JPG encoder. That second pass is not lossless: the encoder makes its own decisions about which fine detail to drop, on top of whatever the WebP encoder already removed.
In practice, at the default quality of 90 the difference is usually hard to see in a photograph. It becomes noticeable if you push the quality low, or if an image goes through several lossy conversions in a row. Each one shaves off a little more, a problem known as generation loss. The best habit is to convert once, from the best source you have, rather than bouncing a file between formats.
Expect the JPG to be somewhat larger than the WebP it came from. For photos, WebP is often 25–35% smaller than JPG at similar visual quality, so matching the look in JPG generally takes more bytes. That is the cost of a file that opens practically everywhere.
Where JPG beats WebP
WebP displays in every current major browser, but the moment an image travels beyond the browser, JPG is the format almost nothing refuses. Convert to JPG when you need to:
- attach photos to an email or message that the recipient may open in an older app;
- send pictures to a print service or photo lab that does not take WebP;
- insert images into documents and presentations in older versions of Microsoft Office;
- upload to a content management system, marketplace or form that only lists JPG and PNG.
JPG is a poor fit for logos, screenshots with small text, diagrams and line art. Its compression works on small blocks of pixels and tends to leave faint halos and smudges around hard edges. For that kind of image, or anything with a transparent background you want to keep, convert WebP to PNG instead.
Filling transparent areas
JPG has no alpha channel, so it cannot store transparency at all. When a WebP contains transparent pixels, such as a sticker, an icon or a product photo cut out from its background, the converter fills them with a background colour you choose. White is the default.
Pick the colour of wherever the image will end up: white for most documents and emails, or the exact hex colour of a dark web page or slide template. Matching the destination avoids a visible box around the subject. If the image genuinely needs to stay transparent, JPG is the wrong target.
WebP and JPG compared
| WebP | JPG | |
|---|---|---|
| Compression | Lossy or lossless | Lossy only |
| Transparency | Supported | Not supported; filled with a background colour |
| Animation | Supported | Not supported |
| File size for photos | Often 25–35% smaller at similar visual quality | Larger for the same visual quality |
| Web browsers | All current major browsers | All browsers |
| Other software | Some older apps and services reject it | Accepted almost everywhere |
| Typical use | Images on modern websites | Sharing, printing, documents |
Choosing JPG quality and size
The quality slider runs from 1 to 100. As a rule of thumb:
- 88 to 95: photos you want to keep, print or edit later. The default of 90 sits here.
- 75 to 87: pictures for email, chat or web forms, where a smaller file matters more than the last bit of detail.
- Below about 70: the savings continue, but artefacts start to show in skies, skin tones and smooth gradients.
Often the bigger saving comes from dimensions rather than quality. If the JPG will be viewed on a phone or inside an email, use Settings → Size to fit it within a sensible maximum width; the aspect ratio is kept and the image is never enlarged. Finally, EXIF metadata such as GPS location is not carried over to the JPG, which is helpful when you share photos publicly.
Animation, colour and batches
- Animated WebP: JPG cannot hold animation, so only the first frame is converted and the converter warns you. If you need the whole animation, keep the original WebP alongside the JPG.
- Colour: output is converted to sRGB. Images prepared for wide-gamut displays, such as Display P3, may look slightly less saturated afterwards.
- Batches: up to 10 images are converted one after another, which keeps memory use low on phones and older computers. A batch of large photos can therefore take a little while to finish.