The WebP Problem: Why the File Will Not Open, and the Fix

Why did that image download as a .webp?

Because your browser asked for it. Not you, and not really the website either.

Every image request your browser makes carries an Accept header listing the formats it can display, and modern browsers put WebP on that list. Image CDNs read it and answer with whichever version is smallest. Cloudflare’s own documentation for its image optimiser states the condition exactly: the WebP version is served only when the Accept header from the browser includes WebP, and only when the WebP is significantly smaller than a recompressed original.[2] The site did not decide you wanted a WebP. Your browser said it could take one, so the CDN sent one, and the same URL that gives you a .webp gives someone else a .jpg.

Why anyone bothers is straightforward. Google, which developed the format, puts lossy WebP at 25-34% smaller than comparable JPEG at an equivalent SSIM quality index.[1] Those are the format author’s own numbers, so treat them as the optimistic end. Here is the same trade measured the other way round, on the photograph at the top of our own homepage:

That gap is why the format is everywhere, and it is also the bill you pay when you convert a download back.

Why will it not open, when it displayed perfectly on the page?

Because displaying an image in a browser and opening a file on your desktop are two different pieces of software, and only one of them was updated.

The browser is the best-maintained image viewer on your machine. Everything else

• the operating system’s own preview, the editor you have had since 2019, the form on a website that accepts uploads - is a separate decoder with a separate release schedule, and each one added WebP whenever it got round to it, if it ever did.

On Windows, WebP support is an optional download. Microsoft’s own list of imaging codecs marks BMP, DDS, DNG, GIF, HD Photo, ICO, JPEG, JPEG XR, PNG and TIFF as native to Windows, while WebP appears as an extension codec you install from the Microsoft Store.[3] That single line explains why the same file opens on your colleague’s laptop and not on yours: one of you has the Store extension and one of you does not.

On macOS the split runs down the middle of the machine. The system frameworks read WebP perfectly well: the built-in sips tool identifies a WebP as format: webp and converts one to JPEG without complaint. Writing one is a different answer entirely:

$ sips -s format webp photo.jpg --out photo.webp
Error: Can't write format: org.webmproject.webp

Which is consistent with what Apple documents for the app most people would reach for: the formats Preview can convert an image to are HEIC, JPEG, JPEG 2000, OpenEXR, PDF, PNG and TIFF.[4] WebP is not on that list. Your Mac can read the file and will not write one.

Upload forms reject it on the extension alone. This is the failure with the least helpful error message, and the example worth naming is Google’s own: its ad platform accepts an uploaded image ad as GIF, JPG or PNG only.[9] WebP is Google’s format and Google Ads will not take one. Any form whose allowed list was written before 2020 behaves the same way, which is most of them.

Does renaming .webp to .jpg fix it?

No. It is the most repeated advice on this topic and it has never worked, so here it is in bytes rather than as an assertion.

A file’s name is not part of the file. WebP’s container specification puts the ASCII characters RIFF, a 32-bit size, then the ASCII characters WEBP at the very start of every WebP file.[5] Copy one to photo.jpg and those twelve bytes are exactly where they were:

$ cp test.webp photo.jpg
$ xxd -l 16 photo.jpg
00000000: 5249 4646 f406 0000 5745 4250 5650 3820  RIFF....WEBPVP8
$ sips --getProperty format photo.jpg
  format: webp

Renaming a file changes its name. The first twelve bytes still say WEBP.

The myth survives because renaming appears to work about half the time. Software that identifies a file by its contents opens the renamed file happily, since it was never reading the extension in the first place. Software that trusts the extension - the upload form, the print shop’s intake, the old editor - accepts it and then fails somewhere deeper, where the message is worse. You have not converted anything. You have removed the one clue that would have told you what went wrong.

Why does “Save image as…” not let you pick a format?

Because it does not convert anything. Save image as… writes the bytes the server sent, under a name you choose. There is no encoder behind that menu item and there never was, which is why it offers no format list on any browser. The file type was decided by the exchange described at the top of this article, several seconds before you right-clicked.

Everything below is a way of adding the conversion step that menu item does not have.

What are the ways to actually get a JPG or PNG?

Five, and they are genuinely different rather than five brands of the same thing.

Route 1: convert it as you save it

A browser extension can add the missing step, because the browser already contains an encoder. Chromium’s canvas encoder accepts exactly three types - image/jpeg, image/png and image/webp (MIMETypeRegistry::IsSupportedImageMIMETypeForEncoding())

• and two of those three are the formats you are trying to get to.[6] The conversion is a decode and a re-encode on your own machine, with no server involved.

With Save Image As Type that is a right-click on the image, then Save Image As Type, then the format. The two format-specific walkthroughs go into what changes in each direction: saving a WebP as JPG covers the white background that replaces transparency and the quality setting, and saving one as PNG covers when lossless is worth the size. Ours is not the only extension that does this; we compare four of them, including our own, and say where a competitor is ahead.

This route only reaches images that are on a page. A WebP somebody emailed you is not on a page, and no browser extension can help with it.

Route 2: ask the site’s image server for a JPG

Underused, and the fastest fix when it applies. Many sites do not store a WebP at all: they store one original and let an image CDN produce whatever format the request asks for. Those CDNs take the format as a URL parameter, so you can ask for the JPG directly.

• Cloudinary uses f_. A URL containing f_auto is choosing the format from your browser; replace it with f_jpg and the same image arrives as a JPG.[7]
• imgix uses fm. fm=jpg or fm=png names the output format outright.[8]
• Others follow the same shape with different spellings: format=jpg, output=jpg, .jpg appended to a path of transformation segments.

How to spot one: right-click the image, copy the image address, and look for res.cloudinary.com, imgix.net, or a run of short parameters like w_800,q_auto,f_auto. If it is there, edit the format parameter and open the result in a new tab. If the URL is a plain path ending in .webp, this route is not available and the file really is stored as a WebP.

Two honest limits. The server is re-encoding for you, so this is not a way to recover an original that was never JPG. And a site that signs its image URLs will reject an edited one.

Route 3: open it in something that already reads WebP

The file is on your disk, so you need software that reads WebP and writes something else. Most people already have it.

• macOS: Preview opens the file, and File > Export offers JPEG, PNG, TIFF, HEIC and the rest of the list Apple documents. No installation, and nothing leaves the machine.
• Windows: install the WebP extension from the Microsoft Store first, which is what makes the format readable system-wide. Paint then opens it and Save as offers JPEG and PNG. Why Windows needs that package at all, and what it does not fix goes through the Windows side properly, including the machines where the Store is blocked.
• Photoshop: 23.2 and later open, edit and save WebP with no plug-in.[10] On 23.1 and earlier the file simply will not open until you install Google’s WebPShop plug-in, which is the version gap most people run into.

This is the right route for a folder of files rather than one image, and the only one of the five that has no per-image cost once the app is open.

Route 4: an online converter

Upload the file, get a converted one back. It works on any machine, including one where you cannot install anything, and that is a real advantage rather than a consolation.

What it costs is that the image leaves your device. It goes to a server you do not control, is converted there, and is held for a period described in terms you did not read. The free tiers are also metered: CloudConvert’s free plan allows 10 conversion credits a day, which is fine for one screenshot and a wall halfway through a folder.[11]

The privacy question is not the same for every image. A meme is a meme. A photograph of a document, a medical scan, a picture of a child, or anything out of a private album is a decision about who gets a copy, and it deserves the two seconds it takes to make it deliberately. Whether online image converters are safe works through that decision in full, including the sites that hand back a correctly converted file with malware in it.

Route 5: the screenshot, and why it is last

It is the first thing most people try, and it does produce a PNG that opens everywhere. It also throws away more than any other route on this page.

You get the image at the size it happened to be displayed, not its real dimensions, which on a page that scales a 2000px photo into a 600px column means you have kept less than a tenth of the pixels. Transparency becomes whatever was behind it. Any interface that overlapped the image is now part of it. And the capture is a fresh lossy compression of an already-lossy image.

Use it when the image is a diagram you need to paste into a message and nothing about quality matters. It is not a conversion, it is a photograph of your own screen.

What does converting cost you?

Every route above that produces a real JPG or PNG pays the same four costs, because they belong to the formats rather than to any tool.

Size. See the table at the top of this article: JPG roughly doubles it and PNG multiplies it by twelve. You are undoing the thing WebP was serving you for.

A second generation of loss. A lossy WebP has already discarded detail. Every JPG you make from it discards a little more, on top of artefacts that are now part of the picture. PNG stops further loss but cannot undo what already happened - it faithfully preserves the artefacts.

Transparency, if the output is JPG. JPG has no alpha channel, so something has to go behind the image, and in practice that is white. A logo with a transparent background becomes that logo on a white rectangle. PNG keeps the transparency, which is most of the reason to choose it.

Metadata. A canvas-based conversion re-encodes pixels and nothing else, so EXIF is not carried across: no camera, no date, no GPS. That is a loss if you were archiving a photograph and a quiet privacy win if you were about to post one.

Should you convert at all?

Not always, and the question is worth asking before you pick a route.

Keep the WebP when the image is going back onto a website, into an app that displays it in a browser view, or into storage where the size is the point. Converting it there costs you bandwidth and gains you nothing.

Convert it when the file has to be opened by software or by a person you do not control: a colleague on an older machine, an upload form, a print shop, an editor that was last updated years ago. Compatibility is worth more than kilobytes the moment the file leaves your hands.

Keep both when you are unsure. They are the same picture, one for the web and one for everything else, and the second one costs you a right-click.

The rest of this cluster goes deeper on the individual decisions: WebP to JPG for photographs and anything you are sending, WebP to PNG for transparency and screenshots, why the file will not open in Windows Photos if that is the machine you are stuck on, and saving as AVIF for the format that is starting to turn up in downloads the same way WebP did.