What does "Use recommended preprompts" do on BetterWaifu?

If you check “Use recommended prepompts” in the BetterWaifu generator‘s Advanced Settings, then the following line is added at the beginning of every prompt:

score_9, score_8_up, score_7_up,

And the following line is added at the beginning of every negative prompt:

score_4, score_3, score_2, score_1, worst quality, bad hands, bad feet,

What do these lines mean and why do we use them?

The “score” tags came as a result of a quirk that the AI models were trained. Not all AI models have this characteristic – only ones based upon Pony Diffusion V6 do.

By putting higher scores in the positive prompt, you’re associated the generation with higher quality images.

Likewise, by putting lower scores in the negative prompt, we’re saying we don’t want association with lower quality images.

The end of the negative prompt, “worst quality, bad hands, bad feet,” is not a part of this scoring system. We’ve simply added this because it’s a solid general purpose negative prompt that improves all generations.

Here’s an example of the difference the preprompt makes: