How to Build an Online Community From Scratch in 2025

By Zach Schleien

I built 18percent to 18,000 members. Here's the step-by-step playbook for building a thriving online community from zero.

I built 18percent from zero to 18,000+ members and nearly 2 million messages. It partnered with Crisis Text Line, the National Suicide Prevention Lifeline, and the National Eating Disorders Association.

Here's the playbook for building a thriving online community from scratch.

Step 1: Define the Purpose (Be Specific)

"A community for entrepreneurs" won't work. It's too broad. People need a reason to join that's more specific than a category.

When I built 18percent, the purpose was specific: a safe Slack community for people dealing with mental health challenges - focused on peer support, not therapy.

The specificity attracted the right people and repelled the wrong ones. Every community needs a clear answer to: "Why would I join THIS community instead of any other?"

Good examples:

• "A community for bootstrapped SaaS founders doing $10K-$100K MRR"
• "A community for women in fintech who are building their first product"
• "A community for remote workers dealing with isolation"

Step 2: Choose the Right Platform

The platform matters less than you think. What matters is where your audience already hangs out.

Slack - Best for professional communities. High engagement, threaded conversations, integrations. (What I used for 18percent) Discord - Best for gaming, crypto, and creator communities. Rich media support, voice channels. Circle - Best for course-based or paid communities. Clean interface, content library built-in. Facebook Groups - Best for non-technical audiences. Easy to join, familiar interface. Geneva - Best for mobile-first communities. Clean, modern, good for local groups.

My recommendation: start with Slack or Discord (free), then migrate to Circle only if you're monetizing.

Step 3: Seed the Community (First 100 Members)

The hardest part is going from 0 to 100. Here's how:

1. Personal invitations. Message 50 people individually. Not a mass blast - genuine, personalized invitations. "I'm building [community name] for [specific purpose]. I think you'd be a great fit because [specific reason]."

2. Cross-pollinate. Share in communities where your target members already are. Not spammy promotion - genuine contribution with a soft mention. "I wrote about this topic in our community - here's the link if anyone wants to go deeper."

3. Content as a magnet. Write about the community's topic and mention the community at the end. I wrote about mental health on LinkedIn and Medium, and every piece drove members to 18percent.

4. Launch with value. Don't launch an empty community and hope people show up. Pre-populate with 5-10 great discussion threads, a welcome guide, and a clear structure.

Step 4: Establish Culture Early

Culture is set by the first 50 members. If those 50 are engaged, thoughtful, and supportive, every new member mirrors that energy.

My rules for 18percent:

• No self-promotion (this was a support space, not a marketing channel)
• No unsolicited advice (listen first, share second)
• No judgment (every story is valid)
• Active moderation (I was in the community daily for the first 6 months)

Your community's rules will be different, but the principle is the same: define the behavior you want, model it, and enforce it consistently.

Step 5: Drive Engagement

Members join for value. They stay for connection. Drive both:

Rituals - Weekly threads, monthly challenges, AMAs with experts. Predictable events give members a reason to come back.

Recognition - Highlight active members. "Member spotlight" posts make people feel seen and encourage participation.

Prompts - Don't wait for organic conversation. Post daily prompts: "What's one thing you're working on this week?" "What's the best advice you've received this year?"

Events - Virtual meetups, workshops, or casual hangouts. I ran Clubhouse rooms that drove engagement and new members simultaneously.

Step 6: Scale Without Losing Soul

The hardest part of community building is scaling without diluting the culture. What worked for me:

Empower moderators. You can't moderate a 10,000-person community alone. Find your most engaged members and give them moderator roles. They already model the culture.

Create sub-groups. As the community grows, create channels or sub-groups for specific interests. This maintains intimacy at scale.

Don't chase growth. It's tempting to optimize for member count. Resist. A 500-person community with 40% daily active rate is more valuable than a 50,000-person community with 2% engagement.

Monetization (Optional)

Community monetization options:

1. Paid membership ($10-50/month for premium access)
2. Sponsored events (brands pay to host workshops or AMAs)
3. Courses/products (sell educational content to your community)
4. Job board (charge companies to post positions to your audience)

I never monetized 18percent directly - the value was in the impact and the network effects it created for everything else I built. Sometimes the community IS the product.

Community building is one of the most rewarding things I've done as a founder. If you're building a community - or a business - and need help with growth strategy, book a free strategy call.