Pure white backgrounds, and why yours is not white

"White background" on a marketplace guideline usually means one exact colour: RGB 255,255,255. A sheet of white paper photographed under normal light comes out somewhere around 235 — light grey, not white — which is why photos that look perfectly clean on your screen still fail the check.

What the camera does to white

A camera meters for an average scene, so a frame that is mostly white is read as over-exposed and pulled down towards grey. Add a colour cast from the light — warm from a bulb, cool from a window, green from a fluorescent tube — and the background is not only darker than white but tinted. On its own each effect is small. Together they put a typical phone photo of a product on white paper somewhere in the 225–240 range with a visible tint, and every pixel of it fails a pure-white test. This is not a skill problem; it is what correct exposure looks like when the subject is white.

Lifting to true white without wrecking the product

The instinct is to raise brightness until the background reads 255. That works, and it also blows out the light edges of your product — the white label, the chrome trim, the reflection along the top of a bottle — because the whole frame moves together. The reliable route is the opposite: separate the product from the background first, then put the product on a background that is *generated* as 255 rather than photographed. That way the background is exactly white by construction and the product keeps every tone it had. It is what this app does, and it is why the background step comes before the framing step.

Checking rather than trusting your eyes

A screen cannot be trusted for this. Two monitors show the same near-white differently, and both look white to a person who is not comparing them side by side. The measurable check is to sample the pixels near the frame edge and read the actual values, which the app does automatically: a background is reported as pure only when the sampled median is exactly 255,255,255, and the audit warns rather than passes when a preset demands pure white and the measurement disagrees. If you are working in another tool, any editor's colour picker on the corner pixel tells you the same thing in two seconds.

The trap: white measured, background not removed

There is a failure mode that looks like success. If the original background could not be separated — a patterned rug, a wooden table with grain, a busy shelf — but the frame is padded out to the marketplace's aspect ratio with white, then the *edges* of the frame really are 255 and a naive check reports pure white. The middle of the frame is still the rug. The audit here calls that out separately for exactly this reason: measuring the edge ring is not the same as removing the background, and a green tick that only measured the ring would be lying to you.