An AI girlfriend app is a chat interface over a large language model, wrapped in a persistent character and a content filter. That is the entire category. What separates a $10 app from a $20 one is rarely the model — it is how well the other two parts are built.
The three parts
The model generates text. Given everything it can currently see, it predicts a plausible next message. It has no memory of your last conversation and no intentions. Every apparent act of will comes from the next two parts.
The character sheet is a block of text the app sends to the model before your message, every single time: who this character is, how they speak, what they know about you, what happened recently. You never see it. When people say an app "has personality," they usually mean this file is well written.
The filter decides what the character may say. It runs before or after the model, sometimes both. It is the reason a conversation can turn into a polite refusal mid-scene, and the reason "uncensored" is the loudest word in this market — apps like Joi and Secret Desires compete mainly on how that filter is tuned.
Why the context window explains the complaints
The model can only see a fixed amount of text at once. That budget is the context window, and it holds the character sheet, the retrieved facts about you, and the recent conversation — all competing for the same space.
When a chat runs long, the oldest turns fall out of the window. The app has not "lost interest" and has not been downgraded. It simply cannot see that part of the conversation any more. Almost every "it used to be better" post is this, and it is why how memory is implemented matters more than how big the model is.
What the character sheet actually holds
Most apps build it from four things:
- A persona: name, age, backstory, manner of speaking.
- Standing facts about you the app has decided to keep.
- A running summary of your history together, rewritten as it grows.
- Recent messages, verbatim.
The apps that feel like someone is still in the room a week later — the reason Nomi scores where it does — are the ones that manage the middle two well. Nothing about that is visible from a pricing page, which is why it takes weeks rather than an afternoon to judge.
What "AI girlfriend" covers in practice
The label stretches across products that barely resemble each other:
- Companion apps built for a continuing relationship, with journaling and mood tracking. Replika is the oldest example.
- Roleplay apps built for scenes and stories rather than continuity.
- Media-first apps where the chat exists to produce images and voice, and Candy AI sits closest to the middle by doing all three inside one subscription.
Deciding which of the three you actually want removes about half the apps on any list, including ours, before price enters the conversation.
What none of them are
They do not know you between sessions unless they were built to store facts and retrieve them. They do not have continuity of self — the character is recreated from text at the start of every turn. And they are not private by default: the conversation is processed on someone's servers, which is the subject of what these apps know about you.
