Every image format tutorial eventually lands on the same three-way comparison — JPEG, PNG, WebP — usually accompanied by a simple rule like "use JPEG for photos, PNG for graphics." That rule is a reasonable starting heuristic, but it skips over why the distinction exists in the first place, which makes it hard to know what to do with the genuinely common cases that don't fit neatly into "obviously a photo" or "obviously a graphic."
The core distinction: lossy versus lossless compression
The real difference underlying the whole "photos vs graphics" heuristic is that JPEG uses lossy compression — it deliberately discards some image information to achieve a smaller file size, information that can't be recovered once it's gone — while PNG uses lossless compression, which shrinks the file size without discarding any actual image data at all. This single distinction explains almost everything else about when to use which format.
JPEG's lossy compression is specifically tuned to discard the kind of information human vision is least sensitive to noticing, which works remarkably well for photographs because photos are full of gradual color transitions and fine detail where a small amount of loss is genuinely difficult to perceive. That same compression approach works poorly on sharp-edged graphics — text, logos, icons, flat-color illustrations — because JPEG's compression technique introduces visible artifacts specifically around sharp edges and abrupt color transitions, the exact features that dominate graphic-style images rather than photos.
Why PNG handles graphics well but photos poorly (in terms of file size)
PNG's lossless approach means it never introduces the edge artifacts that make JPEG look bad on sharp graphics, which is exactly why logos, screenshots, icons, and any image with large flat color areas or text look noticeably cleaner as PNG. The tradeoff shows up in file size: because PNG can't discard any information, compressing a genuinely complex photograph — full of subtle gradients and fine texture that don't compress well without loss — often produces a dramatically larger file than the same image saved as JPEG at a quality level where the loss is essentially invisible to the eye.
PNG's other major advantage, transparency support through an alpha channel, is a separate feature from its lossless compression, but the two commonly get bundled together in people's mental model of the format since PNG is the traditional go-to when you need both.
Where WebP fits into this
WebP is a more modern format that supports both lossy and lossless compression modes within the same format, generally achieving smaller file sizes than JPEG at equivalent visual quality for photos, and smaller file sizes than PNG at equivalent quality for graphics with transparency. In principle, WebP can replace both JPEG and PNG for most practical purposes, and browser support has become nearly universal on the modern web, which is why many sites have shifted to serving WebP as their default image format with a JPEG or PNG fallback for older or more limited contexts.
The reason WebP hasn't fully displaced the older formats despite its technical advantages comes down to ecosystem inertia rather than any real limitation — some older tools, some specific workflows, and some contexts outside the web (certain print or professional editing pipelines) still expect JPEG or PNG specifically, so the older formats remain relevant even where WebP would technically produce a better result.
The genuinely ambiguous middle cases
The simple "photo versus graphic" rule breaks down for images that are genuinely a mix of both — a product photo with sharp graphic text overlaid, a screenshot of a photo-rich webpage, a scanned document with both photographic imagery and crisp text. In these mixed cases, there often isn't a single objectively correct answer; it comes down to which artifact type is more acceptable for your specific use — do you care more about the photo areas looking clean (favoring JPEG or lossy WebP) or the text and sharp edges staying crisp (favoring PNG or lossless WebP)? Testing both and comparing at your actual target file size or quality level is often more reliable than trying to reason it out from the format's general characteristics alone.
A practical decision framework
For a genuine photograph with no transparency or sharp overlaid graphics, JPEG (or lossy WebP if your context supports it) is usually the right call for file size efficiency. For a logo, icon, screenshot, or any image dominated by flat color and sharp edges, PNG (or lossless WebP) avoids the visible compression artifacts JPEG would introduce. For anything that needs transparency, PNG or WebP — never JPEG, which has no transparency support at all. And whenever your target platform supports it, WebP is usually a reasonable default over either older format, given its generally better compression efficiency at equivalent visual quality.
Converting between formats
Our image format converter converts between JPEG, PNG, and WebP directly in your browser, which is useful for testing how a specific image actually looks and compresses in each format before committing to one for your final use case, rather than reasoning about it purely in the abstract.