Integration of LINE App’s Multi-party Chat Features

LINE is consolidating its two multi-person chat types—temporary “Rooms” and long-term “Groups”—into a single Group Chat model. The change aims to simplify the user experience, make all chat features available everywhere, and reduce duplicated server and client resources. A gradual migration strategy is being used to avoid disruption.

Two Original Chat Models

• Rooms were designed for temporary conversations:
  • No room name was required.
  • Invited friends joined immediately without approval.
  • Features such as albums and notes were unavailable.
• Groups were designed for long-term communities:
  • They had names and supported features such as group albums and notes.
  • Invitees had to accept or reject invitations before joining.
• Users often created Rooms without realizing their limitations, then created a new Group later when they needed additional features.

Reasons for Unification

• Users found the distinction between Rooms and Groups difficult to understand.
• Existing conversations could not be converted from Rooms into Groups, forcing users to abandon their conversation history.
• Users frequently created multiple chats with the same members, causing:
  • Cluttered conversation lists.
  • Unnecessary data accumulation on servers.
  • Increased client and server resource usage.
• The unified model standardizes behavior and features while retaining flexibility in how invitations work.

Migrating Groups to Group Chats

• LINE introduced new Group Chat APIs and used dual reads to maintain compatibility with existing Group APIs and storage.
• The migration proceeded gradually:
  1. The new API initially read Group data through a routing layer.
  2. The number of Group Chats was progressively increased.
  3. Eventually, only Group Chats were created.
• Batch processing migrated all existing Group data.
• After migration, LINE stopped dual reads and relied exclusively on the Group Chat model.

Differences Between Rooms and Groups

Invitation Mechanisms

• Groups required invitees to explicitly accept or reject an invitation.
• Rooms added people immediately when they were invited.
• The unified creation flow lets users choose whether invitees should join immediately or confirm participation first.

Feature Availability

• Rooms lacked many Group features because they were intended to be temporary.
• The new model is based on the Group architecture, so all newly created conversations support the full feature set, including future features.

Improving Conversation Discovery

• Users often created a new chat with the same participants instead of finding an older, inactive conversation in a long chat list.
• The new creation workflow displays a hint when an equivalent existing conversation is found.
• Users can then return to the existing conversation, reducing duplicate rooms and improving navigation.

Migration Plans for Existing Rooms

• Conversations created in current LINE versions are already Group Chats.
• Groups created with older app versions are being converted server-side.
• The remaining objective is to migrate existing Rooms so their participants can use the complete set of Group Chat features.

The project is a long-term effort designed to minimize disruption while improving consistency and efficiency. Duplicate conversations with identical participants fell from 15% for Rooms to 0.78% for invitation-free Group Chats, demonstrating the practical impact of the consolidation.