Why you keep ending up with WebP files
WebP is Google's image format, and since about 2020 most websites serve it because it produces noticeably smaller files than JPEG at the same quality. Save a picture off a web page and a .webp file is what you get.
The trouble starts when you try to use it. Plenty of software still will not open one: older versions of Photoshop, most print shops' upload forms, a lot of accounting and job-management software, some email clients, and almost anything that predates 2021. You have a perfectly good picture in a format the thing you need it for refuses to read.
Converting it to JPG solves that, because JPG has been universally supported since the 1990s and there is essentially nothing that cannot open one.
What you lose
Two things, and they are worth knowing about before you convert everything.
Size. JPG files are typically 25 to 35 per cent larger than the WebP they came from at comparable quality. That is the whole reason WebP exists. If the file is going on a website, converting it to JPG is a step backwards.
Transparency. WebP can have a transparent background. JPG cannot, at all. Any transparent area has to become a solid colour, and without one specified it comes out black, because an unfilled image is transparent black underneath. That is how logos end up on black squares. Here you pick the colour and it defaults to white.
There is also a second, quieter loss: WebP files are often already lossy, and re-encoding to JPG compresses a second time. Generation loss on a single hop is hard to see at quality 90, but it is real, and it stacks if you keep converting back and forth.
When to convert and when not to
Convert when something you need cannot read WebP: a print shop, an older program, a client who says "it won't open". Convert when you are sending a photo to somebody and have no idea what they will open it with.
Do not convert when the image is going onto a website. You would be making it bigger and slower for no benefit, since every current browser reads WebP perfectly well. And do not convert a logo or an icon with a transparent background unless you have somewhere sensible for that background to go: PNG is the right target for those.
Every other converter sends your file to a server
Every other converter sends your file to a server. Most cap you at a couple of files a day unless you pay, some watermark the output, and nearly all want an email address.
This runs on the page, in your browser. There is no upload, no limit on how many files, no maximum size, no watermark, no daily quota and no account. You can check the first part yourself: open the network tab and convert something, and nothing goes out.
Server time costs money, which is why other people meter it. This costs us nothing because it runs on your machine, so there is nothing to meter.
Common questions
Why do I keep getting sent WebP files I cannot open?
Because most websites have served WebP since about 2020, since it produces smaller files than JPEG at the same quality, so saving a picture off a web page usually gives you a .webp file. Plenty of software still cannot open one, including older versions of Photoshop, most print shops' upload forms and a lot of accounting and job-management software.
Does converting WebP to JPG make the file bigger?
Yes, typically. JPG files are usually 25 to 35 per cent larger than the WebP they came from at comparable quality, which is the whole reason WebP exists, so converting a WebP meant for a website is a step backwards.
What happens to a transparent background when converting WebP to JPG?
It has to become a solid colour, because JPG cannot store transparency at all. Left unspecified it comes out black, since an unfilled image is transparent black underneath, which is how logos end up on black squares. Here you pick the colour and it defaults to white.
Does converting WebP to JPG lose quality in any other way?
Yes, a quieter loss. WebP files are often already lossy, so re-encoding to JPG compresses the image a second time. That generation loss is hard to see on a single conversion at a high quality setting, but it is real and it stacks if the file is converted back and forth repeatedly.
When should I convert WebP to JPG, and when should I not?
Convert when something you need cannot read WebP, such as a print shop, an older program or a client whose software will not open it. Do not convert an image going onto a website, since every current browser reads WebP perfectly well, and do not convert a logo or icon with a transparent background, since PNG is the right target for those.
Is anything uploaded to convert a WebP file, and are there limits?
No. It runs on the page in your browser, with no upload, no limit on file size or number of files, no daily quota, no watermark and no account. You can check that nothing is sent anywhere by opening your browser's network tab while converting.