I would like to use my phone for leisure on chol hamoed. I know tying is permitted-but what about, say, browsing the Internet or watching videos? Thanks.
it would have the same halachic significance as using computers which is permitted.
R. Cohen writes:
R’ Moshe Feinstein (Hilchos Chol Hamoed Zichron Shlomo p78) held that typing cannot be considered ma'aseh uman and providing it was of relevance to Yom Tov, would be permissible. R’ Shlomo Zalman Auerbach (Shemiras Shabbos Kehilchasa 66:n209) compares it to using stamps which the Eshel Avraham allows. While storing data to a disc is improving the disc, and therefore tantamount to boneh, providing the work was necessary for Yom Tov (or would cause a significant loss, etc.), it would be muttar. In a letter to R’ Avraham Avraham (Nishmas Avraham OC 4:340:4) R’ Shlomo Zalman explained that displaying letters isn’t problematic, as it merely shows light. R’ Ovadia Yosef (Yabia Omer OC 8:48) paskens leniently, too for the same reason.
While the Acharonim don’t discuss playing computer games, it seems that it should be muttar as, like driving to an outing, it can be considered relevant to the Chag and no Issur is involved.