Chat, for GitHub
Ranked in these QuestionsQuestion Ranking
Pro Unlimited public rooms for free
Pro Has apps for OSX, iOS and Chrome
Pro Has full Markdown support
Pro Free for small teams
If you have a small team, or you are a startup that doesn't need more than 25 per private room, you don't need money to pay for Gitter.
Pro Has many developer-friendly integrations
Integrations for Trello, Jenkins, Travis CI, Heroku, Sentry, BitBucket, HuBoard, Logentries, Pagerduty & Sprintly are available.
Pro Has many developer-friendly integrations and support for custom webhooks
Trello, Jenkins, Travis CI, Heroku, Sentry, BitBucket, HuBoard, Logentries, Pagerduty & Sprintly
Pro Has an IRC bridge
Pro Has a Windows 8 app
Con Non-free / Propritary Software
It cannot be self-hosted, you have no ownership over the data, and if the company behind Gitter dies, you are screwed.
Con GitHub only
A GitHub account is required to use Gitter.