Why WebP Images Fail to Open in KakaoTalk — Browser Support Isn't App Support
"This image looks fine in my browser, but the preview breaks when I send it over KakaoTalk" — anyone who's worked with WebP images has probably run into this at some point. This guide explains why "a format the browser supports" and "a format a messaging app can actually handle" aren't the same thing, and where that gap comes from.
1. What WebP is, and why it's so widely used
WebP is an image format Google introduced in 2010 that can produce noticeably smaller file sizes than JPEG or PNG at comparable visual quality, which is why it's so widely used for web performance optimization. Every major modern browser today — Chrome, Firefox, Safari, Edge — fully supports WebP. That's exactly where the problem starts: the fact that "browsers support it" doesn't mean "every piece of software supports it."
2. Browser support ≠ app support: decoders are separate per piece of software
Displaying an image on screen requires code capable of interpreting (decoding) that format. Browsers ship with their own built-in WebP decoder, but messaging apps like KakaoTalk, or an OS's own photo gallery app, often rely on an entirely separate image-processing library from the browser's. In other words, "WebP has been a standard on the web for a long time" and "did this specific version of this specific app already include a WebP decoder at that point in time" are two different questions. And for an app that pre-generates and caches thumbnails/previews server-side, if that server-side pipeline itself was never updated to handle WebP, previews can break regardless of whether the client supports the format.
3. Where it actually broke: older iOS, and some older Android
Apple's system-level support for WebP was incomplete on versions of iOS before iOS 14. Because of this, there were reported cases on iOS versions prior to that point where saving a WebP image to the Photos app, or sharing it via apps like KakaoTalk, produced a broken preview or an outright failed save. Some older Android devices and OS versions had similar issues. Exactly when this was fully resolved varies by device, OS, and app version combination, so it's safer to treat this as a risk that can still exist in some environments, rather than assuming "everything after a certain version is 100% safe."
4. Why this is never fully resolved — an inherent side effect of a fragmented ecosystem
Mobile OS and app ecosystems have no way to force every user onto the latest version automatically. There's always some share of older devices, users who delay updates, and devices with OS updates restricted by corporate policy. That's why even a format that became a standard long ago can't be guaranteed to work across 100% of the actual installed user base — that's simply a characteristic of the mobile ecosystem. This isn't unique to WebP; it's a pattern that recurs every time a new codec or format tries to gain adoption.
5. The practical fix
If your target device or app is uncertain, or you need to account for older environments, converting WebP to JPEG before sharing is the safest option. JPEG has been the default supported format for essentially every piece of image-processing software since the 1990s, so it carries virtually no compatibility risk. Conversely, if the image is only ever used in a modern-browser web context (say, uploaded to your own website), keeping it as WebP is the better choice for file size. In short, the format you should pick depends on where the image is going.
FAQ
Q. If I have the latest version of KakaoTalk, is WebP fully safe?
A. The KakaoTalk app itself handles WebP better in newer versions, but the issue depends not just on the app version but also on the recipient's device OS version (particularly older iOS/Android). If you can't control the recipient's environment, converting to JPEG is safer.
Q. Do other apps like Instagram or Facebook have the same problem?
A. The same underlying principle applies, though to varying degrees. Large platforms often re-encode uploaded images into their own format on the server side, which tends to reduce issues compared to KakaoTalk, but there have still been reported cases of problems on older devices in specific situations.
Q. Does converting WebP to JPG reduce image quality?
A. That depends on the quality setting used for the conversion. Set the quality high enough (90 or above, for example) and the visible difference is minimal. Keep in mind, though, that JPG doesn't support WebP's transparency — transparent areas get filled with a background color instead. If you need to preserve transparency, convert to PNG instead.
Q. Why didn't every app support WebP from the start?
A. When WebP was introduced in 2010, an enormous installed base of devices and software was already locked into the JPEG/PNG ecosystem, and it's simply not realistic to roll a new codec out to every piece of software instantly. Browsers adopted it first, and support spread from there — mobile OS and app ecosystems tend to catch up later.