Invert the colours of an image
Flip every colour to its opposite. Nothing leaves your device.
What to know
Each colour channel is replaced with its opposite, so white becomes black and red becomes cyan. Transparency is left untouched.
Inverting twice returns the original exactly, because the operation is its own reverse.
Questions
Is anything uploaded to a server?
No. Every tool on this site runs inside your browser using standard web APIs. There is no upload, no account, no logging and no server holding your data afterwards. You can confirm it by opening your browser's developer tools and watching the network tab stay empty while you work.