What Is Moon Phase Compatibility?

I’ve never been much of a TikTok girlie, but every so often, I get sucked down the rabbit hole. During this summer’s annual deep dive, I found myself both amused and absolutely entranced with the vision of two moons approaching each other from opposite ends of the screen, meeting in the middle to form one moon. This was the Moon Phase Compatibility Test trend. Good on the algorithm for knowing this would be irresistible to my astrologer eye. I watched video after video by creators testing their compatibility with their crush, their partner, and even—especially after the popularity of Barbie—their mom. 

What’s so interesting about this trend is that it strays from pop astrology’s usual focus on personality traits, and instead focuses on the visual appearance of the moon. This excites me as an astrologer as it gets back to astrology’s roots of looking up at the night sky. With this trend, people aren’t fixated on the moon’s sign, but on the moon’s phase (which is an important indicator of the energy that one brings to life). While it thrills me as an astrologer to see people engaging with their moon phase, does that automatically mean this trend is legit? Here’s the breakdown of what the Moon Phase Compatibility Test is, and what the results can tell you about other people and yourself.

The Moon Phase Compatibility Test is a TikTok trend in which you use one of many apps to compare the moon phase you were born under to the natal moon phase of your crush, lover, bestie, etc. to see if it's a match. There are eight different moon phases one can be born under: New, Waxing Crescent, First Quarter, Waxing Gibbous, Full, Waning Gibbous, Last Quarter, and Waning Crescent. Each of these moon phases brings a particular energy to life. 

The general consensus on TikTok is that moon phases “match” when they come together and form a Full Moon. So for example someone born at a New Moon (when there is no light in the sky) would always match with someone born at a Full Moon (when the moon is completely lit up); someone born at a Waxing Crescent (when the moon is visible as a sliver in the evening sky) would always match with a Waning Gibbous (when the moon is losing light but still very visible throughout the night). According to the trend, the combinations that form a Full Moon are thought of as “Soulmates,” whereas anyone born under the same moon phase is a “Twin Flame.” Some sites and apps (like this one) include a percentage ranking with each phase combination.

Some have taken the categorization even further, pointing out phases that speak to “temporary soulmates,” “psychic connection,” or someone “on a completely different path.”