When Google Gemini generates an image, it applies two distinct watermarking mechanisms. Most people are only aware of one — the visible star icon. But there's a second, hidden layer that works very differently.
The visible watermark: the sparkle icon
The visible watermark is a four-pointed star (✦) placed in the bottom-right corner of every Gemini-generated image. It's semi-transparent and consistent in size across all images.
Because it's a visual overlay on top of the image pixels, it can be reversed mathematically. Tools like Lumina Watermark use the known blend formula to reconstruct the original pixel values underneath.
SynthID: the invisible watermark
SynthID is Google DeepMind's imperceptible watermarking technology. It encodes a signal directly into the image's pixel values in a way that is invisible to the human eye but detectable by specific algorithms.
SynthID survives common modifications like cropping, compression, and color adjustments. It cannot be removed by visual processing tools — including Lumina.
Quick comparison
- check_circleVisible star icon — removable with Lumina Watermark
- check_circleSynthID invisible signal — cannot be removed by any visual tool
- check_circleBoth are applied automatically to all Gemini image outputs
Why does this matter?
If you only need to clean up the visible mark for design or presentation purposes, Lumina handles that completely. If you need the SynthID signal removed — that is not possible without Google's own system.