Chapter 6 GET POST

sendChatMessage – Send Chat Message

The sendChatMessage endpoint allows you to send a chat message to the public chat of a running meeting via the API. The message appears as a system or custom-named message visible to all participants. This endpoint was introduced in BigBlueButton 3.0.

This endpoint is only available in BigBlueButton 3.0 and later. It is minimally documented in the official API documentation. Details on error codes, rate limiting, and character encoding are not officially specified. undocumented

Endpoint

GET https://api-guide.bbbserver.com/bigbluebutton/api/sendChatMessage?<parameters>&checksum=replace-with-checksum

Required Parameters

Parameter Type Required Default Description
meetingID String Yes — The meeting identifier of the target meeting.
message String Yes — The message content (1 to 500 characters). Special characters are escaped automatically. HTML and Markdown are not supported.

Optional Parameters

Parameter Type Required Default Description
userName String No System The display name of the sender (maximum 255 characters). undocumented

Example Request

https://api-guide.bbbserver.com/bigbluebutton/api/sendChatMessage?meetingID=replace-with-meeting-id&message=Welcome+to+the+conference!&userName=System+Admin&checksum=replace-with-checksum

Example Response

A successful call returns the following XML: 

<response>
  <returncode>SUCCESS</returncode>
  <messageKey></messageKey>
  <message></message>
</response>

Error Responses

messageKey Description
checksumError The checksum is invalid.
missingParamMeetingID The meetingID parameter was not provided.
meetingNotFound The meeting does not exist or is no longer running.
validationError message is missing, empty, or exceeds 500 characters; or userName exceeds 255 characters.
On bbbserver.de, this endpoint is available on all plans running BigBlueButton 3.0 or later. You can call it using your API credentials found in the server management dashboard.

Use Cases

  • Send automatic welcome messages when a meeting starts.
  • Deliver system notifications from external applications (e.g. "Recording will begin in 5 minutes").
  • Build bot integrations that react to events and post messages.
  • Create moderation tools that send announcements to all participants.

Limitations

Be aware of the following restrictions when using this endpoint:

  • Only public chat messages are supported. Sending private messages to individual users is not possible.
  • No Markdown or HTML formatting. The text is rendered as plain text only.
  • Messages are limited to 500 characters.
  • The meeting must be running. Messages cannot be sent to ended meetings.
  • Sending messages to breakout rooms is not supported.

If you need to send longer messages, consider splitting the content into multiple API calls. Keep in mind that rapid successive calls may be subject to rate limiting, although the exact limits are not officially documented.

Frequently Asked Questions

This endpoint was introduced in BigBlueButton 3.0. It is not available in earlier versions such as 2.6 or 2.7.

No. The sendChatMessage endpoint only supports the public chat. There is currently no API endpoint for sending private messages to individual participants.

The API returns a validationError response. The message is not sent. You must shorten the text to 500 characters or fewer before retrying.

No. The message content is treated as plain text. Any HTML tags or Markdown syntax will be displayed literally rather than rendered.

If you do not specify a userName, the message appears with the sender name "System". This is suitable for automated notifications and system alerts.

No. The sendChatMessage endpoint only targets the main meeting room. Sending messages to breakout rooms is not supported by the API.