The description field on YouTube allows 5,000 characters. If you have a 10-minute video, you should be able to fit a good description into this amount of space. However, if you have less than 5,000 characters, you may have to make a few compromises. You can use double quotes around phrases, or use longer descriptions.
Keywords also appear in the metadata of your video. These keywords should be placed near the beginning of your video description.
Creating a descriptive and attractive description is important for YouTube SEO. A good description will persuade viewers to watch your video, which will increase your SEO efforts.
You should also choose tags that are relevant to your video. Having too many tags can negatively affect your rankings.
You can use up to 15 hashtags on YouTube, but you should only use a few. If you use more than fifteen, YouTube will stop working on your video. You will also need to follow the guidelines for hashtags.