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Groups

Groups let multiple people chat together. Unlike channels, any member can post messages.

Groups list

Groups vs Other Conversation Types

Feature Direct Message Group Channel
Participants 2 people Multiple members Unlimited subscribers
Who can post Both Any member Owner only
Join method Add contact Invite (private) or join (public) Subscribe
Encryption Yes Yes Yes
Best for Private 1:1 Team chats, friends Announcements

Types of Groups

Private Groups

  • Invite-only - Members must be invited by an admin
  • Hidden - Don't appear in public discovery
  • Secure - Group key shared only via encrypted invites

Public Groups

  • Open - Anyone can join by knowing the group ID
  • Discoverable - Can appear in group announcements
  • Convenient - Easier to share, less secure

Creating a Group

Step by Step

  1. Open Mycel and go to the Chats tab
  2. Tap the Groups sub-tab
  3. Tap the + (floating action button)
  4. Enter a Group Name (required)
  5. Optionally add a Description
  6. Choose Private or Public:
  7. Private: Members must be invited
  8. Public: Anyone can join with the group ID
  9. Tap Create Group

You're now the group's admin and can start inviting members.

What Happens Behind the Scenes

When you create a group:

  1. A unique group ID is generated
  2. A 256-bit encryption key is created for the group
  3. You become the admin (only admins can invite/remove members in private groups)
  4. The group is ready to use immediately

Inviting Members

To a Private Group

As the admin:

  1. Open the group chat
  2. Tap the group name/header to view group info
  3. Tap Invite Members or Add Member
  4. Select contacts from your contact list
  5. Tap Send Invite

The invite is encrypted specifically for each recipient. When they accept:

  • They receive the group key
  • They're added to the member list
  • They can see group messages and post

To a Public Group

For public groups, you can:

  • Share the group ID directly (they can join themselves)
  • Use the invite flow above (works the same way)

Invites work offline

Group invites travel through the mesh like regular messages. Recipients can accept invites even if you're not online at the same time.

Receiving and Accepting Invites

When someone invites you to a group:

  1. You'll receive a notification (if enabled)
  2. The invite appears in your message list
  3. Tap the invite to view group details:
  4. Group name
  5. Who invited you
  6. Current member count
  7. Tap Join Group to accept

After joining:

  • The group appears in your Groups tab
  • You can see message history (from the time of your join)
  • You can post messages

Declining Invites

Simply ignore the invite or dismiss it. You won't be added to the group.

Managing Group Membership

Viewing Members

  1. Open the group chat
  2. Tap the group header
  3. View the member list with roles:
  4. Admin - Can invite/remove members
  5. Member - Can read and post

Adding Members (Admin Only)

  1. Open group info
  2. Tap Add Member or Invite
  3. Select contacts
  4. Send invites

Removing Members (Admin Only)

  1. Open group info
  2. Find the member in the list
  3. Tap their name or the remove option
  4. Confirm removal

Removed members keep old messages

When you remove someone, they lose access to new messages but can still read messages they received before removal. The group key is not rotated.

Promoting to Admin

Admins can promote other members:

  1. Open group info
  2. Tap a member's name
  3. Select Make Admin

Posting in Groups

Posting works like direct messages:

  1. Open the group
  2. Type your message
  3. Tap Send

Your message is:

  1. Encrypted with the group key
  2. Sent to all members via the mesh
  3. Delivered as members come into contact with relays

Message Delivery in Groups

Group messages travel the same way as direct messages - through the mesh. Each member receives the message independently, so delivery times may vary per member.

Status Meaning
Pending Waiting for relay opportunity
Forwarding Traveling through mesh
Delivered Reached at least one member

Leaving a Group

To leave a group:

  1. Open the group chat
  2. Tap the group header
  3. Scroll to the bottom
  4. Tap Leave Group
  5. Confirm

After leaving:

  • You're removed from the member list
  • You won't receive new messages
  • The group remains in your history (archived)
  • You can't rejoin private groups without a new invite

Group Notifications

Muting a Group

To mute notifications for a specific group:

  1. Open the group
  2. Tap the group header
  3. Toggle Mute on
  4. Choose mute duration (1 hour, 8 hours, 1 day, forever)

Muted groups still receive messages, but won't trigger notifications.

Global Group Settings

In Settings > Notifications:

  • Mesh Group notifications - Toggle alerts for the built-in mesh broadcast
  • Popup notifications - Show floating alerts
  • Sound / Vibration - Audio and haptic feedback

Group Sync and CRDT

Groups use a special technology called CRDT (Conflict-free Replicated Data Type) to sync membership across all members, even when they're offline.

How It Works

  • Each member change (add/remove) is recorded with a timestamp
  • When members reconnect, changes are merged automatically
  • The same final state is reached regardless of the order changes are received

What This Means for You

  • Offline-friendly - Membership changes sync whenever devices meet
  • Consistent - Everyone eventually sees the same member list
  • No conflicts - Simultaneous changes are handled automatically

Tips for Groups

For Better Delivery

  • Keep the app running - Background operation helps relay group messages
  • More members = better mesh - Each member can relay to others
  • Be patient - Group messages may take longer than DMs (more recipients)

For Privacy

  • Use private groups for sensitive discussions
  • Verify invites - Make sure you know who invited you
  • Admin carefully - Only promote trusted members to admin

For Organization

  • Use descriptive names - Makes groups easy to find
  • Archive old groups - Swipe left to archive inactive groups
  • Pin important groups - Swipe right to pin frequently used groups

Troubleshooting

"I can't add someone to my group"

  • Are you an admin? Only admins can invite members in private groups
  • Do you have their contact? You can only invite people in your contact list
  • Is the invite stuck? Check Mesh Lab > Queue for pending invites

"I didn't receive a group invite"

  • Check your message list - Invites appear as special messages
  • Is the sender nearby? Invites travel through the mesh like messages
  • Check permissions - Ensure Mycel has notification permission

"Group messages aren't arriving"

  • Check connectivity - Go to Mesh Lab > Nearby to see if you're connected
  • Is the group muted? Check group settings
  • Are other members online? Group messages need relay paths

"I accidentally left a group"

  • Private groups - Ask an admin to send a new invite
  • Public groups - Rejoin using the group ID

Technical Details

For developers and curious users:

Property Value
Encryption AES-256-GCM with shared group key
Key distribution ECIES (X25519 + XChaCha20-Poly1305)
Membership sync 2P-Set CRDT
Max members ~100 (practical limit)
Message TTL 24 hours default

Deep Dive: Private Groups Technical Details

Next: Channels | Mesh Broadcast | Contacts