WebP is lossy or lossless depending on the encoder, with alpha and animation. GIF is a palette of at most 256 colours, all-or-nothing transparency, and animation. ImageMagick sits between the two, and this page says exactly what happens to a WEBP file on the way to becoming a GIF one.
What runs when a WEBP file becomes GIF
ImageMagick 6.9.12, on a machine we rent and watch. Your WEBP file is uploaded once, ImageMagick runs once, the GIF comes back, and neither file is kept. WEBP to GIF is one of the 3649 pairs that engine was probed on with a real file, which is why it has a page here and why the pairs the probe could not prove do not.
What survives from the WEBP into the GIF
The pixel dimensions of your WEBP file. The GIF comes out the size the WEBP went in, because nothing on this path resizes anything.
What WEBP to GIF costs you
Colour depth. GIF holds 256 colours at most, so a photographic WEBP gets quantised and its gradients band.
If a model is going to read the GIF
A GIF file is pixels, and pixels are expensive for a model to read. Handed this GIF, an assistant spends its budget looking at the picture rather than reading it, and it will paraphrase what it thinks it saw. If your WEBP is mostly words, the useful move is to pull the text out of it, not to change which picture format holds it.
WEBP to GIF, measured rather than promised
Running WEBP to GIF against the real engine with a real file, ImageMagick wrote 4,744 bytes of GIF in 0.1 seconds, machine otherwise idle. That is one WEBP file on one day and not an average, which is why the number is given together with the file that produced it.
The WEBP to GIF verdict was reached by a format signature, meaning at least four bytes unique to the format were found at the right offset. Which check was used matters, because they do not all prove the same thing, and a status code of 200 proves nothing whatsoever about whether the GIF file has anything inside it.
The same WEBP file, sent somewhere else
Other outputs the probe measured out of a WEBP file, so the cost of choosing GIF can be read against something. Sizes do not compare across engines, because each family was probed with its own WEBP witness file.
WEBP to PDF: 94,782 bytes in under a tenth of a second, verified by a format signature.
WEBP to JPG: 2,340 bytes in under a tenth of a second, verified by a format signature.
WEBP to PNG: 4,003 bytes in under a tenth of a second, verified by a format signature.
WEBP to TIFF: 72,264 bytes in under a tenth of a second, verified by a format signature.
Other ways into GIF, and what they measured
Among the published routes into GIF, WEBP is the number 11 largest output of the 19 measured. The witness files differ, so this ranks the probe run and not your document.
PDF to GIF: 9,463 bytes in 0.1 seconds.
JPG to GIF: 3,487 bytes in 0.1 seconds.
3GP to GIF: 164,004 bytes in 0.1 seconds.
AVI to GIF: 173,720 bytes in 0.2 seconds.
BMP to GIF: 3,799 bytes in 0.1 seconds.
What we will not pretend about WEBP to GIF
A WEBP file over 25 MB is refused before the upload finishes rather than after it, so you do not wait for a rejection.
A WEBP to GIF run that passes 30 seconds is killed, and the ImageMagick process is killed with it. A run left behind would sit on one of the machine's two cores until somebody noticed.
No text is read out of the WEBP anywhere on this path. Converting a picture to GIF never turns it into words, whatever the picture happens to contain.
ImageMagick was not saturated at sixteen simultaneous conversions: it held 47.5 a second while latency moved from 0.22 s to 0.34 s, and the service memory did not move off 51 MB. That is the measured headroom behind WEBP to GIF, not a marketing number.
One WEBP file at a time, chosen in the browser. There is nothing else to set up and nothing else on offer.
WEBP to GIF: what people ask
What actually converts my WEBP file to GIF?
ImageMagick does it, 6.9.12, on a machine we rent and watch. Not a browser trick and not somebody else service: the WEBP file is uploaded once, ImageMagick runs once, the GIF comes back, and neither file is kept afterwards.
How long does WEBP to GIF take?
On the file the probe used, ImageMagick took 0.1 seconds and wrote 4,744 bytes of GIF. That is one real measurement on one real WEBP file, not an average and not a promise about yours: a larger WEBP takes longer, and past 30 seconds the run is stopped.
What do I lose going from WEBP to GIF?
The one to know about first: Colour depth. GIF holds 256 colours at most, so a photographic WEBP gets quantised and its gradients band.
Does the GIF come out the same size as the WEBP?
The same pixel size, yes: nothing on this path resizes anything, so the GIF is as wide and as tall as the WEBP was. The number of bytes is a different question and usually moves a long way, which is normally the reason for doing this at all.
Is WEBP to GIF free?
There is a free allowance every month, and one WEBP to GIF conversion costs half a credit against it. When the allowance runs out the tool says so and stops, rather than quietly handing you a worse GIF.