The RTCRtpTransceiver property direction is a string that indicates the transceiver's preferred directionality.

The directionality indicates whether the transceiver will offer to send and/or receive RTP data, or whether it is inactive or stopped (terminated). When setting the transceiver's direction, the value is not applied immediately. The current direction is indicated by the currentDirection property.

A string with one of the following values:

"sendrecv"

Transceiver offers to send and receive RTP data:

• RTCRtpSender: Offers to send RTP data, and will do so if the remote peer accepts the connection and at least one of the sender's encodings is active.
• RTCRtpReceiver: Offers to receive RTP data, and does so if the remote peer accepts.

"sendonly"

Transceiver offers to send but not receive RTP data:

• RTCRtpSender: Offers to send RTP data, and will do so if the remote peer accepts the connection and at least one of the sender's encodings is active.
• RTCRtpReceiver: Does not offer to receive RTP data and will not do so.

"recvonly"

Transceiver offers to receive but not set RTP data:

• RTCRtpSender: Does not offer to send RTP data, and will not do so.
• RTCRtpReceiver: Offers to receive RTP data, and will do so if the remote peer offers.

"inactive"

Transceiver is inactive:

• RTCRtpSender: Does not offer to send RTP data, and will not do so.
• RTCRtpReceiver: Does not offer to receive RTP data and will not do so.

"stopped"

This is the terminal state of the transceiver. The transceiver is stopped and will not send or receive RTP data or offer to do so. Setting this value when the transceiver is not already stopped raises a TypeError.

• RTCRtpSender: Does not offer to send RTP data, and will not do so.
• RTCRtpReceiver: Does not offer to receive RTP data and will not do so.

When setting the value of direction, the following exception can occur:

InvalidStateError DOMException

The receiver's RTCPeerConnection is closed or the RTCRtpReceiver is stopped.

TypeError

The value is being set to stopped when the current value is anything other than stopped.

The direction property can be used to set or get the transceiver's preferred directionality.

Updating the directionality does not take effect immediately. If the new value of direction is different from the existing value, renegotiation of the connection is required, so a negotiationneeded event is sent to the RTCPeerConnection. A direction value (other than stopped) is then used by RTCPeerConnection.createOffer() or RTCPeerConnection.createAnswer() in order to generate the SDP message created those methods. For example, if the direction is specified as "sendrecv", the corresponding SDP a-line indicates the directionality:

a=sendrecv

The new directionality takes effect once the negotiation process is completed and the new session description is successfully applied.

The transceiver's current direction is indicated by the currentDirection property.

• RTCRtpTransceiver.currentDirection