Properties and Constraints

Properties and Constraints — CometChat documentation.

This page lists the properties and constraints applicable to various CometChat systems.

API Keys

Property	Constraints
API key value	System-generated, 40-character hexadecimal string
API key name	Max 100 characters, UTF8mb4 (supports all languages and emojis; one emoji = 2 characters)
API key scope	authOnly — can only create auth tokens for users. Referred to as “Auth Key” in the dashboard and docs. fullAccess — can perform all REST API operations (create/update/delete users, groups, messages, etc.). Referred to as “REST API Key” in the dashboard and docs.
Maximum API keys per app	25

Users and Groups

Property	Constraints
Maximum members per group (all features enabled)	300 (with delivery/read receipts and typing indicators)
Maximum members per group (without receipts and typing indicators)	100,000
Maximum groups per user	2,000
Maximum friends per user	1,000
Maximum auth tokens per user	100 active (rolling retention — oldest tokens archived when limit exceeded)
Maximum groups per app	No limit
Maximum unread messages per user	No limit
Maximum users per app	No limit
Maximum bot users per app	25
User/Group ID (uid, guid)	Max 100 characters, alpha-dash (a-z, 0-9, -, _), no spaces. Automatically lowercased.
User/Group name	Max 100 characters, UTF8mb4 (supports all languages and emojis)
User/Group avatar	Must be a valid URL, max 3,000 characters. Image is not stored by CometChat — URL must remain accessible.
User profile link	Must be a valid URL, max 3,000 characters
User/Group metadata	Max 5 KB (within the 10 KB POST request body limit)
User/Group tags	Max 25 tags, each up to 100 characters, UTF8mb4
Group password	Max 100 characters
Group description	Max 255 characters, UTF8mb4
Presence subscriptions	Active for up to 1,000 concurrent online users per app. Beyond 1,000, presence notifications are not sent. Applies across friends, role-based, and all-user subscriptions.
Typing indicators (groups)	Sent for groups with up to 1,000 online members
Unread message counts (groups)	Not updated for groups with more than 300 members
Delivery/read receipts (groups)	Sent for groups with up to 300 online members

Roles

Property	Constraints
Maximum roles per app	25
Role ID	Max 100 characters, alpha-dash (a-z, 0-9, -, _), no spaces. Automatically lowercased.
Role name	Max 100 characters, UTF8mb4 (supports all languages and emojis)
Role description	Max 255 characters, UTF8mb4
Role metadata	No limit

Messages

Property	Constraints
Maximum file upload size	100 MB per message (includes file + entire POST body)
Maximum message size (including metadata)	65,536 characters (~65 KB). Applies to the message JSON payload, not file uploads.
Message data object	Arbitrary JSON, UTF8mb4. Reserved keys: text, attachments, custom_data, metadata. Max 10 KB for the data object. Attachment file size is counted separately.
Message tags	Max 25 tags, each up to 100 characters, UTF8mb4
Conversation tags	Max 25 tags, each up to 100 characters, UTF8mb4
Soft-deleted messages retained	Yes
Permanently deleted messages (via API) retained	No

Calling

Property	Constraints
Maximum users per call	50
Default video frame rate	30 FPS
Video resolution	Min 180p, max 720p (varies by layout and user bandwidth)
Media encryption	SRTP
Audio codec	OPUS
Video codec	H.264