How it actually works
Your photo never leaves your browser, we don't upload it to any server, and no external AI processes it. All the analysis happens on your own phone or computer: we read the pixel colour from the central area of the photo (where the water usually is, not the edge or the tiles) and calculate its hue, saturation and lightness to classify it into one of 4 categories.
Why it's a rough guide, not an exact diagnosis
The colour in a photo depends on the light at the time, whether there's shade, the type of camera and even the phone's own filter. A blue pool photographed in heavy shade can come out darker than it really is. So if the result doesn't match what you see with your own eyes, trust your eyes, and if you have real doubts, the reliable way to know for sure is still measuring the water parameters with test strips.