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About this tool
Compare working space gamuts, see what assigning the wrong profile does to each primary, and learn when to convert instead.
An ICC profile is the label that says what a file's RGB numbers actually mean, and this explainer makes that concrete. It computes each working space's gamut as the area of the triangle its primaries span in CIE 1931 xy — sRGB covers 0.1121, Adobe RGB 0.1512 and ProPhoto RGB 0.2770 — then shows exactly where each primary lands when a file is read under the wrong profile, and spells out the difference between assigning and converting.
Open ICC Profile Explainer on AltFTool — it loads instantly in your browser.
Upload or drag in the file you want to work with.
Adjust the settings and preview the result.
Download the finished file to your device.
Areas are computed from the published primaries, not quoted from memory.
Each primary's authored and displayed chromaticity is listed side by side.
One states what changes the numbers and what changes the appearance.
Assigning leaves every pixel value untouched and changes only the label that says what those numbers mean, so the appearance changes. Converting recalculates the pixel values so the colour looks the same in the new space, so the numbers change and the appearance does not.
Usually the file is Adobe RGB or Display P3 but is untagged, so the browser falls back to sRGB. Adobe RGB's green primary sits at x 0.21, y 0.71 against sRGB's 0.30, 0.60, so greens and cyans collapse toward neutral while red and blue, which share the same primaries, look unchanged.
Use sRGB for anything delivered to the web or a general audience, because untagged files are assumed to be sRGB anyway. Adobe RGB is worth it when the file is going to CMYK print, where its extra cyan-green coverage survives the conversion — and it should be edited at 16-bit.
Yes once the space is meaningfully larger than sRGB. ProPhoto RGB covers about 2.5 times the chromaticity area of sRGB, so 8-bit spreads the same 256 codes per channel over that wider range and gradients band visibly.