You can use hashtags in video titles or descriptions to help viewers find your video when they search for a specific hashtag.

Use hashtags to find videos

Hashtags are an easy way for you to find videos about popular topics. There are two ways to find videos using hashtags:

• Search YouTube for a hashtag.
• Click on a hashtag in a video title, above a video title, or in the video description.

You'll see a results page that shows videos with the hashtag. 

Add hashtags to your videos

Follow the steps to upload a video, then enter the hashtag (#hashtag #example) in the video's title or description. 

• Hashtags in the title and description will be hyperlinked.
• If there are no hashtags in the title, the first three hashtags in the description will show above the video title.

Users can click on hashtags that appear in your video title, above your video title or in the description to go to that hashtag's search results page to see related videos.

Hashtag use policies

Like all content uploaded to YouTube, hashtags must meet our Community Guidelines. Make sure to follow these policies when using hashtags:

• No spaces: Hashtags don’t contain any spaces. If you want to have two words in a hashtag, you can join them together (#TwoWords, #twowords).
• Over-tagging: Don't add too many tags in a single video. The more tags you add to a video, the less relevant they become for users who are searching. If a video has more than 15 hashtags, we'll ignore all hashtags on that video. Over-tagging may result in the removal of your video from your uploads or from search.
• Misleading content: Don't add hashtags that are not directly related to the video. Misleading or unrelated hashtags may result in the removal of your video. Learn more about our Misleading Metadata Policies or watch the .

  Misleading metadata on YouTube video

• Harassment: Don't add a hashtag with the purpose of harassing, humiliating, intimidating, exposing, or threatening an individual or group. Violating this policy will result in the removal of your video. Learn more about our Harassment & Cyber Bullying Policies.
• Hate speech: Don't add any hashtags that promote violence or hatred against individuals or groups. Don't add hashtags that contain racist, sexist, or other slurs. Violating this policy will result in the removal of your video. Learn more about our Hate Speech Policy.
• Sexual content: Adding sexual or explicit hashtags may result in the removal of your video. Remember, if a video is intended to be sexually provocative, it is less likely to be acceptable for YouTube. Learn more about our Sexual Content Policy. 
• Vulgar language: Use of profanity or offensive terms in your hashtags may lead to an age-restriction or removal of your video.
• Non-hashtags: While adding hashtags is allowed, adding ordinary descriptive tags or repetitive sentences in the description is (still) prohibited. Violating this policy will result in the removal of your video or penalties being applied to your video. Learn more about our Misleading Metadata Policies.

* Nguồn: Youtube