In Open-source software (OSS) development, developers usually relied on social media platforms to promote and seek for collaborators. Hacker News is one of the social news platforms that most software developers use to share the news and software development. Yet, it is unclear how Hacker News post affects software popularity and productivity. To tackle this question, we use a quasi-experimental framework to estimate the impact of Hacker News appearances on GitHub repository popularity and productivity. We collected 18253 repositories that appeared in Hacker News as treated repositories and other two control repository pools along with Difference-in-Differences (DiD) to estimate the causal effect. We found that a Hacker News post can statistically significantly increase repository popularity (stars and forks) while the effect on productivity (pushes) act as a motivational catalyst for smaller projects rather than established ones. Furthermore, we use Difference-in-Difference-in-Differences (DDD) to analyze the repository characteristics and found that repositories with organizational backing, funding and comprehensive documentation will amplify the project’s engagement with the Hacker News post. These findings reflect to OSS developers to build the strong project credibility before posting to convert temporary visitors into lasting community growth.