How much do tags actually matter now?
YouTube has said tags play a smaller role than title, description and thumbnail click-through in deciding rankings - but they still help in one specific way: catching misspellings of your main keyword and giving the algorithm a bit more context about your video's topic, especially for newer channels with less watch-time history to go on. The tags field accepts up to 500 characters total, so this tool keeps the list within that budget automatically rather than generating more than YouTube will actually accept.
Why tags generated from both your title and topic keywords together
Combining words from your actual title with your separately-entered niche keywords produces longer-tail tag variants that neither input alone would generate - a title word paired with a topic keyword often matches a more specific search phrase than either the full title or a bare topic keyword would on its own.
Why newer channels benefit from tags more than established ones
YouTube's ranking system leans heavily on actual watch-time and engagement history once a channel has built some of it up - a newer channel with little of that history yet gives the algorithm less to go on, which is exactly the gap tags can help fill a little by providing extra topical context and catching keyword misspellings while that watch-time signal is still thin.
Why copying a competitor's tags directly tends to backfire
Tags only function as topic signals alongside a video that genuinely matches them - pasting tags from an unrelated or only loosely related video doesn't borrow any of that other video's ranking success, and can actively confuse how your own video gets categorized, which is why tags generated from your own actual title and topic are more useful than ones copied from someone else's video.