Unlike a web button, a CTA inside a video is delivered by **voice, captions or graphics**: a line like "please like and subscribe," an animated subscribe button in the corner, an arrow graphic in the captions.
**Timing** decides its effect. Asking right at the start burdens viewers who have not received value yet; asking only at the end misses the many who already left. A common approach is **one short ask** right after the viewer got value (after the key information) and another on the end screen (→ end-screen).
Ask for one thing at a time. "Subscribe, like, comment, bell, share" all at once converts none of them. Giving a reason ("so you don't miss the next one") helps.
When to use
Use it when designing conversion moments in channel-growth videos, ads and promos. Limit it to one or two asks per video.