Video tutorial on Youtube:

These are the websites used to increase subscribers, views and likes (or increase watch time) for the YouTube channel that I have stumbled across and tested. The video above has been tested on link 01 and link 02. The remaining links you try to research to see how the results.

(Update) Some links have the function to increase the number of followers, likes, … for Facebook, Website, Twitter, …

1) Sites used to increase subscribers, views and likes:
Link 01: https://www.subpals.com/
Link 02: https://www.ytpals.com/
Link 03: https://www.submenow.com/
Link 04: https://www.like4like.org/
Link 05: https://ytbpals.com/
Link 06: https://traffup.net/
=> Website: https://traffup.net/
=> Twitter: https://traffup.net/twitter/
=> Retweets: https://traffup.net/retweets/
=> Facebook: https://traffup.net/likes/
=> Instagram: https://traffup.net/instagram/
=> Youtube: https://traffup.net/youtube/
=> Pinterest: https://traffup.net/pinterest/
=> SoundCloud: https://traffup.net/soundcloud/
Link 07: https://onlywire.com/page/youtube
Link 08: https://www.ytmonster.net/
Link 09: https://www.instafollowers.co/
=> Instagram: https://www.instafollowers.co/free-instagram-followers
=> Facebook: https://www.instafollowers.co/free-facebook-followers
=> YouTube: https://www.instafollowers.co/free-youtube-subscribers
=> SoundCloud: https://www.instafollowers.co/free-soundcloud-likes
=> Pinterest: https://www.instafollowers.co/free-pinterest-followers
Link 10: https://www.sonuker.com/
Link 11: https://www.qqtube.com/en/
Link 12: https://kingviews.net/
(Will update if found)
Link of Vietnam: https://hoatube.com/

2) Web increased hours of viewing (the current site is no longer active):

Link : The website above in the video is closed. No new links have been found to increase watch time.

PS:
All the above links are for testing only and it is important not to abuse. Finally wish you quickly achieve 1000 subscribers and 4,000 hours of viewing for Youtube to consider making money.