How does the YouTube algorithm determine the freshness of video content?

YouTube's algorithm considers several factors to determine the freshness of video content:

1. **Upload Date:** The most straightforward indicator of freshness is the upload date. Newer videos are generally considered fresher than older ones.

2. **View Velocity:** YouTube measures how quickly a video gains views after being uploaded. Videos that attract a lot of views shortly after being published are often considered fresher and may be more prominently featured in search results and recommendations.

3. **Engagement Metrics:** Metrics like likes, comments, shares, and watch time are important indicators of viewer engagement. Videos that receive high levels of engagement shortly after being uploaded are likely considered fresher and may be promoted more by the algorithm.

4. **Topic Relevance:** If a video is on a trending or current topic, it may be considered fresher even if it's not brand new. YouTube may prioritize showing such content to users interested in that topic.

5. **User Behavior:** YouTube tracks user behavior to understand what kinds of content users find fresh and engaging. For example, if a user frequently watches new videos from a particular creator or on a specific topic, YouTube may prioritize showing them fresh content in those categories.

6. **Session Time:** YouTube may prioritize showing fresh content to keep users on the platform longer. If users are more likely to continue watching after viewing a fresh video, the algorithm may boost the visibility of fresh content.

7. **Relevance to Search Queries:** Freshness can also be determined by how well a video matches current search queries. If a video is relevant to trending or current events, it may be considered fresher in search results.

Overall, the YouTube algorithm aims to surface content that is not only recent but also engaging and relevant to users' interests and search queries.