Gemini Watermark Remover: Clean the Visible Sparkle on WatermarkUndo

Use WatermarkUndo to remove the visible Gemini sparkle watermark from an image and download the cleaned result as PNG. Drop your image onto the page or tap to choose it. Processing runs in your browser, with no server upload, no registration, and no daily usage limit.

The tool currently handles images. Video is not supported.

Add your image and check the watermark’s position

Choose an image your browser can decode. The homepage lists PNG, JPG, WebP, AVIF, and GIF as examples.

WatermarkUndo targets the visible Gemini sparkle at Gemini’s standard placements. If the mark sits somewhere else, use the nudge sliders to adjust the cleanup position.

A mark outside the usual placement calls for the documented nudge controls before you judge the cleanup result.

Understand what the tool changes

WatermarkUndo reverses the blend between the image and the semi-transparent white sparkle. It uses the watermark’s alpha map and the formula published on its homepage:

original = (watermarked − alpha × 255) / (1 − alpha)

This formula describes the cleanup method, not an accuracy percentage.

The homepage states that pixels outside the watermark box remain untouched. Image dimensions stay unchanged, and the surrounding image’s pixel values are preserved in the PNG output.

The download is always PNG, so saving the cleaned result does not introduce another round of lossy compression.

Inspect the downloaded result

Keep the original beside the downloaded PNG so you can judge the marked area without losing sight of the surrounding picture.

As a practical review, inspect whether the sparkle remains visible, whether its former location looks acceptable, and whether the surrounding picture still matches the original. These are suggested acceptance checks, rather than a built-in quality test.

On WatermarkUndo, a cleaned download means a PNG with the visible Gemini sparkle addressed; it does not mean SynthID has been removed.

SynthID and other invisible or steganographic watermarks are outside this tool’s scope.

Set the watermark size, position, and removal strength

The homepage’s tool panel contains these labels and instructions:

Watermark size
Auto — detect from image dimensions
96 × 96 px
48 × 48 px
Auto follows Gemini's own placement: 96 px with a 64 px margin on images larger than 1024 px on both sides, otherwise 48 px with a 32 px margin.
Nudge horizontally 0 px
Nudge vertically 0 px
Removal strength 1.00×
Scales the watermark's opacity before the reverse blend. Lower it if a dark halo appears, raise it if a faint ghost of the sparkle is left behind.
Show the watermark box on the result

Let Auto choose the size from both image dimensions

Auto uses the 96 × 96 px watermark with a 64 px margin when both the image width and height are greater than 1024 px. Otherwise, it uses the 48 × 48 px watermark with a 32 px margin.

Both dimensions matter. If either side is 1024 px or smaller, the stated Auto rule selects the smaller watermark. The size menu also provides the two explicit size options shown above.

Correct placement with the horizontal and vertical controls

If the sparkle is away from its standard placement, use Nudge horizontally and Nudge vertically to adjust the cleanup position along the corresponding axis. Their displayed starting values are 0 px.

Use Show the watermark box on the result to inspect the cleanup region while checking its alignment with the sparkle.

Adjust strength to match the remaining artifact

The panel displays Removal strength 1.00×. This control scales the watermark’s opacity before the reverse blend.

Follow the panel’s direction: lower the strength if a dark halo appears; raise it if a faint ghost of the sparkle remains. These symptoms call for opposite adjustments, so increasing strength is not the answer to every imperfect result.

My practical recommendation is to consider manual retouching if correcting the placement and following the documented strength guidance still leaves an unacceptable result. That is an editorial stopping recommendation, not an additional rule stated by the tool.

Judge the saved picture by the area you needed to fix. Accept the result when that area is suitable for your intended use.