What YouTube actually reads from descriptions
Two parts of your description carry the heaviest SEO weight. (1) The first 150 characters — what shows above the 'show more' fold and what YouTube's algorithm weighs most. (2) The first paragraph (first ~250 chars total) — secondary ranking signal.
Everything below that helps for viewer experience (timestamps, links, social) but barely moves rankings. Front-load your keyword + value in the first 150 chars. Don't open with 'Welcome to my channel!' or 'Like and subscribe!' — those waste the ranking real estate.
