Each chatbot wears a name and an avatar that its users design for it.
It can even have a backstory, personality traits and interests selected by its creator.
Now the avatars are set to become even more realistic - and will be able to hold video calls with their creators.
"We’re moving to very realistic avatars, to a much more premium and high-quality experience with the avatars in Replika, and augmented reality, mixed reality, and virtual reality experiences, as well as multimodality," founder and CEO Eugenia Kuyda told The Verge.
"There will be a much better voice experience, with the ability to have true video calls, like how you and I are talking right now, where you can see me and I will be able to see you.
"That will be the same with Replika, where Replika would be able to see you if you wanted to turn on your camera on a video call."
The digital companion is fairly sophisticated in that it can come up with a human-sounding reply to its users' questions.
Replika has a team of roughly 50 people, mostly engineers but also psychologists, who make sure the AI can hold a good conversation.
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"Replika, from the very beginning, was all about AI friendship or AI companionship and building relationships," Kuyda explained.
"Some of these relationships were so powerful that they evolved into love and romance, but people didn’t come into it with the idea that it would be their girlfriend."
People mostly text with their avatars, but Kuyda said that an increasing number of users are using voice mode to converse with these 'virtual beings'.
It appears there's a growing appetite from users to have even more intimate relationships with their avatars.
"For some people, it means marriage, it means romance, and that’s fine," added Kuyda. "That’s just the flavor that they like."
She continued: "But in reality, that’s the same thing as being a friend with an AI.
"It’s achieving the same goals for them: it’s helping them feel connected, they’re happier, they’re having conversations about things that are happening in their lives, about their emotions, about their feelings."