To determine the best red light therapy for hair growth, I tapped three WIRED tech reviewers who've dealt with hair loss themselves. We assessed red light therapy caps, hands-free helmets with full scalp coverage, and low-level laser therapy or photobiomodulation devices for 16 weeks. Along the way, we reviewed the research, spoke with dermatologists, and tracked ease of use. These are the favorites that produced meaningful results and earned our trust.