Slack is a messaging app for collaboration. It didn't take the tech-savvy SEO community long to create channels and then subgroups built around specific SEO topics, such as link building. Good Slack link building communities include:

Online Geniuses - While free to join, applications have to be manually approved before the application receives an email invitation. Online Geniuses is the most popular community on the list; they have live events and well-known industry professionals as members.

Backlinks - Free to join but applicants must fill out a form and wait for an email invitation. Join the group if you are looking for guest post opportunities. The are more industry‐specific channels as well.

Traffic Think Tank - Traffic Think Tank requires a monthly fee of over $100, however, there are industry experts, private webinars, live events and more to make this community worth the cost.

Marketers Chat - Marketers Chat has a strong focus on affiliate marketing and SEO. It is free to join.

BIGSEO - While BIGSEO is a small community compared to the others on this list, it is work joining. The close community will help you build relationships, which is the best way to get quality backlinks. There is no fee but applicants must fill out a form and wait for an email invitation.

There are a number of online forums where you can exchange link building ideas, but forums typically have people wanting advice, not offering it. Some are littered with individuals selling links from private blog networks and contextual blog post links with reviews of their service from other members.

No matter how much experience you have with link building, you can always learn something new. Slack communities are perfect for finding proven, actionable advice. While you can benefit from members advice, you should also give back and share your own experiences. For more information click here https://www.reddit.com/r/SEO/comments/bjeziq/lookingforseoslackcommunities/.