Alternate universes change the setting, but the best AUs keep the soul of the character. Headcanons help you find what stays the same when everything else shifts—and what new details emerge.
Find the core first
Before you drop your character into a coffee shop or a space station, run them through the Character Headcanon Generator in canon. Ask for habits, internal logic, or "how they react under stress." Those traits often translate across AUs: the control freak in canon might still need to organize the spice rack in a modern AU. Start from the AI Headcanon Generator homepage and build a small "core" list.
Then twist for the AU
Use the same generator with a different focus—or the Random Headcanon Generator for "what if they were in X situation?" You'll get ideas that feel like them but fit the new world. For ship dynamics in the AU, the Relationship Headcanon Generator can show how the same two people would act in a different context. Everything is linked from the homepage.
Test the voice
Does your medieval knight still sound like themselves in a college AU? Run them through the Incorrect Quotes Generator with the new setting in mind. If the dialogue feels off, you might need to adjust the headcanons. The main site lets you switch between all four tools without losing your place.
Whether you're writing a canon divergence or a full AU, the AI Headcanon Generator gives you the tools to keep your characters recognizable—and discover what changes when the world does.