The question looks like it’s asking which planets are considered the best candidates for alien life. The short answer is: we do not know of any planet that definitely has aliens, but scientists have identified a small set of promising worlds in the habitable zone where liquid water could exist.

Promising candidates

Recent reports highlight about 45 rocky exoplanets as strong candidates for potential habitability, with a more conservative estimate lowering that to 24.

Some of the best-known examples are:

  • Proxima Centauri b.
  • TRAPPIST-1 d, e, f, and g.
  • Kepler-186f.
  • LHS 1140 b.
  • Kepler-442b.

What “possible” means

These planets are not confirmed to host life. They are only considered promising because they sit in or near the “habitable zone,” where temperatures might allow liquid water under the right atmospheric conditions.

Bottom line

So, if you mean “the only planets aliens might live on,” the honest answer is: none are confirmed, but a few dozen exoplanets are the main candidates scientists watch most closely.

TL;DR: no confirmed alien planets yet, but Proxima Centauri b and the TRAPPIST-1 planets are among the leading candidates.