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Invisible Watermark and the NSFW Checker#


InvokeAI does not apply watermarking to images by default. However, many computer scientists working in the field of generative AI worry that a flood of computer-generated imagery will contaminate the image data sets needed to train future generations of generative models.

InvokeAI offers an optional watermarking mode that writes a small bit of text, InvokeAI, into each image that it generates using an "invisible" watermarking library that spreads the information throughout the image in a way that is not perceptible to the human eye. If you are planning to share your generated images on internet-accessible services, we encourage you to activate the invisible watermark mode in order to help preserve the digital image environment.

The downside of watermarking is that it increases the size of the image moderately, and has been reported by some individuals to degrade image quality. Your mileage may vary.

To read the watermark in an image, activate the InvokeAI virtual environment (called the "developer's console" in the launcher) and run the command:

invisible-watermark -a decode -t bytes -m dwtDct -l 64 /path/to/image.png

The NSFW ("Safety") Checker#

Stable Diffusion 1.5-based image generation models will produce sexual imagery if deliberately prompted, and will occasionally produce such images when this is not intended. Such images are colloquially known as "Not Safe for Work" (NSFW). This behavior is due to the nature of the training set that Stable Diffusion was trained on, which culled millions of "aesthetic" images from the Internet.

You may not wish to be exposed to these images, and in some jurisdictions it may be illegal to publicly distribute such imagery, including mounting a publicly-available server that provides unfiltered images to the public. Furthermore, the Stable Diffusion weights License, and the [Stable Diffusion XL License][] both forbid the models from being used to "exploit any of the vulnerabilities of a specific group of persons."

For these reasons Stable Diffusion offers a "safety checker," a machine learning model trained to recognize potentially disturbing imagery. When a potentially NSFW image is detected, the checker will blur the image and paste a warning icon on top. The checker can be turned on and off in the Web interface under Settings.


There are a number of caveats that you need to be aware of.


The checker is not perfect.It will occasionally flag innocuous images (false positives), and will frequently miss violent and gory imagery (false negatives). It rarely fails to flag sexual imagery, but this has been known to happen. For these reasons, the InvokeAI team prefers to refer to the software as a "NSFW Checker" rather than "safety checker."

Memory Usage and Performance#

The NSFW checker consumes an additional 1.2G of GPU VRAM on top of the 3.4G of VRAM used by Stable Diffusion v1.5 (this is with half-precision arithmetic). This means that the checker will not run successfully on GPU cards with less than 6GB VRAM, and will reduce the size of the images that you can produce.

The checker also introduces a slight performance penalty. Images will take ~1 second longer to generate when the checker is activated. Generally this is not noticeable.

Intermediate Images in the Web UI#

The checker only operates on the final image produced by the Stable Diffusion algorithm. If you are using the Web UI and have enabled the display of intermediate images, you will briefly be exposed to a low-resolution (mosaicized) version of the final image before it is flagged by the checker and replaced by a fully blurred version. You are encouraged to turn off intermediate image rendering when you are using the checker. Future versions of InvokeAI will apply additional blurring to intermediate images when the checker is active.

Last update: July 26, 2023
Created: November 30, 2022