Microsoft Teams (free) | Google Hangouts (free) | Slack (free) | Slack (paid) | Discord | ||
https://products.office.com/en-us/microsoft-teams/free | https://hangouts.google.com/ | https://slack.com/ | https://slack.com/ | https://discordapp.com/ | https://www.whatsapp.com/ | |
Video | up to 10 people | 1:1 only | up to 15 people | up to 9 people | up to 4 people | |