Why you have a WebP in the first place
WebP is Google's image format, and it is genuinely good: at the same visual quality it is usually a quarter to a third smaller than the equivalent JPEG, which is why so many sites now serve it. Every current browser displays it without complaint.
The trouble starts once the file leaves the browser. Save an image
from a web page and you get a .webp, and then discover
that the program you wanted to use it in has never heard of the
format — older Photoshop versions, Word and PowerPoint on some
builds, print shops, a surprising number of phone gallery apps and
most things that upload a profile picture. Converting to JPEG trades
the file-size advantage for something everything can read.
How the conversion works
Every file is decoded to raw pixels and then compressed again as a JPEG. That is a real conversion rather than a rename, and it has to be: WebP and JPEG are different codecs with different maths behind them, so there is no way to reuse the existing compressed data.
Because it is a re-encode, quality is a choice rather than a guarantee, and the slider is always shown. The default of 92% is high enough that the difference is hard to see side by side. Dropping to around 80% is a reasonable trade for a much smaller file; below 70% you start to see the usual JPEG artefacts — soft blocks in flat colour, halos along hard edges.
Do not be surprised if the JPEG comes out larger than the WebP you started with. That is the format difference working against you, and it is normal. The results list shows both sizes so you can see exactly what the conversion cost.
Transparency and animation
WebP supports both; JPEG supports neither. Transparent areas are filled with white before encoding, which is what an image editor does when you save a transparent image as a JPEG. If keeping transparency matters, JPEG is the wrong destination — PNG is the format you actually want.
An animated WebP becomes a single still frame, because a JPEG file cannot hold more than one. There is no setting that changes this; it is a property of the format.
Where your files go
Nowhere. The decode and re-encode both happen in your browser using the file you selected, and this page has no upload endpoint to send anything to. You can load the page, turn off your connection, and it will still convert.
Re-encoding also strips most metadata as a side effect, so camera details and any embedded location generally do not survive the trip. That is usually welcome when you are about to share a photograph, and worth knowing if you were relying on it being there.
Edge cases
A WebP file that fails to decode — genuinely corrupted, or an
unusually old WebP variant a particular browser's decoder does not
support — is reported as unreadable and skipped rather than producing
a broken JPG. Because format sniffing reads the actual file contents,
a file with a .webp extension that is not really WebP
data (a mislabelled JPEG, for instance) is still handled: it is
identified correctly and converted along the normal path for
whatever it actually is, as long as it is one of the accepted image
types.
Common mistakes
Converting a WebP to JPG "to preserve quality" is backwards — every conversion here re-encodes, so quality can only stay the same or drop, never improve. If the goal really is to avoid any further quality loss, keep the WebP and only convert the copy you need elsewhere. The other common surprise is expecting the JPG to be smaller: WebP is usually the more efficient format at a given visual quality, so converting to JPEG typically costs some file size even at the default 92% setting, which is the opposite of what most format conversions do.
If your source file is JFIF or an ordinary JPEG rather than WebP, use JFIF to JPG instead — it can copy the JPEG bytes through unchanged rather than re-encoding them. If the picture is a HEIC photo from an iPhone, start at HEIC to JPG. And if you need a lossless output rather than JPEG, PNG is the format that keeps every pixel — see JFIF to PNG, which also accepts WebP as an input.
Limits
Thirty files and 25 MB each per batch, checked before the conversion starts. Every file is held in memory while it is decoded, so a phone will reach its limit well before a laptop does. Large images take a moment; the progress appears against each file rather than as a single bar, so you can see which one is being worked on.
PNG, JPEG, GIF and BMP are accepted as well, and are converted the same way — decoded, then written out as JPEG. Files that are not images are rejected as they are added, with the reason given, rather than failing partway through a batch. Converting several files in one batch offers a single ZIP download once at least two results are ready, alongside each file's individual download link.