Fitness YouTube is the best free coaching that has ever existed and also an advertising business. Both things are true at once, and the useful approach is to sort channels by what they are specifically reliable for rather than ranking them overall.
For evidence-led lifting
Jeff Nippard. The default recommendation, and deservedly. Reviews the literature, states effect sizes rather than just directions, and is comfortable concluding that something does not matter much. Sells programs, and is reasonably upfront about it.
Renaissance Periodization. Mike Israetel has genuine academic credentials and the volume and hypertrophy frameworks here are the most widely adopted in the space. The delivery is deliberately provocative, which is a style question rather than an accuracy one.
House of Hypertrophy and Flow High Performance. Smaller, drier, and arguably more careful than either of the above. No charisma budget, which is exactly why they are worth your time.
For technique
Alan Thrall. Barbell technique explained without theatre. Squat, bench, deadlift, press, and an unusual willingness to say when something is a matter of preference rather than correctness.
Squat University. Movement mechanics and the rehab-adjacent end of lifting. Strongest on why a position hurts; weaker when it drifts into broader health claims.
Athlean-X. Genuinely useful on technique and on working around niggles, from someone with real credentials. Discount the certainty: a great deal of the catalogue is framed as exercises you should never do, and that framing is more confident than the evidence.
For running and endurance
The Running Channel for approachable coverage of the questions beginners actually have.
Global Cycling Network and Global Triathlon Network for their sports, with the same caveat every large channel carries: the sponsored content is clearly a business.
Endurance content in general is more prone to gear-review-as-content than lifting is, so it is worth being deliberate about whether you are watching training advice or a shopping channel.
How to judge a channel yourself
Have they ever changed their mind in public? A channel that has never revised a position across years of output is not being careful, it is being consistent, and those are different things.
Do they cite specifics you could check? “Studies show” is not a citation. A named study with a stated effect size is.
Does the conclusion require their product? Advice that always terminates in a program purchase or a supplement code is advertising with a research section.
Do they say when something does not matter? This is the strongest single signal. Most training variables are minor, and a channel that treats everything as critical is optimising for watch time.
The audio version of this list is the best health and fitness podcasts, and the written one is the best strength training books.