WebRTC's getStats() API exposes over 200 metrics across 10 stat types. The W3C spec defines them formally. This reference explains what they actually mean - what values to expect, what causes anomalies, and how to act on them.

Each entry links to a detailed KB article with practical interpretation guidance.

Before we begin, it might make sense for you to understand the structure of the results coming from getStats(). Here is a short video explainer:

Inbound RTP Stream Stats

Metrics for media streams you are receiving. This is where you find packet loss, jitter, decoded frames, concealment, and all inbound quality signals.

Core Counters

Metric	What it tells you
packetsReceived	Total RTP packets received for this stream
bytesReceived	Total payload bytes received
headerBytesReceived	RTP header bytes (overhead indicator)
packetsLost	Cumulative packets lost as reported by RTCP
packetsDiscarded	Packets received but dropped (e.g., arrived too late)

Network Quality

Metric	What it tells you
jitter(ms)	Packet arrival time variance - higher means more network instability
jitterBufferDelay	Total time samples/frames spent in the jitter buffer
jitterBufferEmittedCount	Count of samples/frames emitted from jitter buffer
jitterBufferMinimumDelay	Minimum delay the jitter buffer targets
jitterBufferTargetDelay	Current target delay of the jitter buffer
jitterBufferFlushes	Times the jitter buffer was flushed (quality disruptions)

Audio Quality

These metrics only appear for audio channels.

Metric	What it tells you
audioLevel	Current audio level (0.0 silent to 1.0 max)
totalAudioEnergy	Cumulative audio energy - useful for RMS calculation
totalSamplesDuration	Total duration of audio samples received
totalSamplesReceived	Total audio samples received
concealedSamples	Audio samples generated locally to hide packet loss
silentConcealedSamples	Concealed samples that were silence
concealmentEvents	Number of concealment events
insertedSamplesForDeceleration	Samples inserted to slow down playout
removedSamplesForAcceleration	Samples removed to speed up playout

Video Quality

These metrics only appear for video channels.

Metric	What it tells you
framesReceived	Total video frames received
framesDecoded	Total video frames successfully decoded
framesDropped	Frames dropped before rendering (performance issue)
framesRendered	Frames actually rendered to the user
framesPerSecond	Current frame rate
frameWidth	Current decoded frame width
frameHeight	Current decoded frame height
keyFramesDecoded	Total keyframes decoded
framesAssembledFromMultiplePackets	Frames that required multiple packets
qpSum	Sum of QP values - indicates compression level
totalDecodeTime	Total time spent decoding
totalInterFrameDelay	Sum of inter-frame delays
totalSquaredInterFrameDelay	For jitter calculation on frame delivery
totalAssemblyTime	Total time assembling frames from packets
totalProcessingDelay	Total processing delay from receipt to decode
freezeCount	Number of video freezes detected
totalFreezesDuration	Total duration of video freezes
pauseCount	Number of video pauses
totalPausesDuration	Total duration of video pauses
interruptionCount	Stream interruptions detected
totalInterruptionDuration	Total duration of interruptions
minPlayoutDelay	Minimum playout delay set by the application

Error Correction & Retransmission

Metric	What it tells you
fecPacketsReceived	Forward Error Correction packets received
fecPacketsDiscarded	FEC packets that arrived but weren't needed
fecBytesReceived	Bytes from FEC packets
retransmittedPacketsReceived	NACK-triggered retransmissions received
retransmittedBytesReceived	Bytes from retransmitted packets
nackCount	NACKs sent requesting retransmission
firCount	Full Intra Requests sent (keyframe requests)
pliCount	Picture Loss Indications sent

Corruption Measurement

Metric	What it tells you
corruptionMeasurements	Number of corruption measurements taken
totalCorruptionProbability	Cumulative corruption probability
totalSquaredCorruptionProbability	For variance calculation

ECN (Explicit Congestion Notification)

Metric	What it tells you
packetsReceivedWithCE	Packets marked with Congestion Experienced
packetsReceivedWithECT1	Packets with ECN-Capable Transport mark
packetsReportedAsLost	Packets reported as lost in RTCP
packetsReportedAsLostButRecovered	Lost packets that were later recovered

Outbound RTP Stream Stats

Metrics for media streams you are sending. Covers encoding performance, bitrate, retransmissions, and quality limitations.

Core Counters

Metric	What it tells you
packetsSent	Total RTP packets sent
bytesSent	Total payload bytes sent
headerBytesSent	RTP header bytes (overhead indicator)
retransmittedPacketsSent	Packets sent as NACK retransmissions
retransmittedBytesSent	Bytes from retransmitted packets

Encoding & Video

These metrics only appear for video channels.

Metric	What it tells you
framesEncoded	Total video frames encoded
framesSent	Total video frames sent
framesPerSecond	Current outbound frame rate
frameWidth	Current encoded frame width
frameHeight	Current encoded frame height
hugeFramesSent	Frames much larger than average (spike indicator)
qpSum	Sum of QP values - tracks compression aggressiveness
totalEncodeTime	Total time spent encoding
totalEncodedBytesTarget	Target bytes the encoder aimed for
totalPacketSendDelay	Time packets waited before being sent

Bitrate & Bandwidth

Metric	What it tells you
targetBitrate	Current encoder target bitrate
qualityLimitationDurations	Time spent limited by CPU, bandwidth, or other factors

Feedback Received

Metric	What it tells you
nackCount	NACKs received from the remote side
firCount	FIR requests received
pliCount	PLI requests received

ECN

Metric	What it tells you
packetsSentWithECT1	Packets sent with ECN marking

Remote Inbound RTP Stats

Metrics reported by the remote peer about streams you sent. This is your view into how the other side is receiving your media - their packet loss, jitter, and round-trip time.

Metric	What it tells you
packetsReceived	Packets the remote received from you
packetsLost	Packets the remote reports as lost
jitter(ms)	Jitter as measured by the remote receiver
roundTripTime(ms)	Current round-trip time to the remote peer
totalRoundTripTime	Cumulative RTT for averaging
roundTripTimeMeasurements	Number of RTT measurements taken
fractionLost	Fraction of packets lost in the last reporting interval

ECN (Remote Side)

Metric	What it tells you
packetsReceivedWithCE	Congestion-marked packets at remote
packetsReceivedWithECT1	ECN-capable packets at remote
packetsReportedAsLost	Packets reported lost by remote
packetsReportedAsLostButRecovered	Lost packets recovered at remote
packetsWithBleachedECT1Marking	ECN marks stripped by the network

Remote Outbound RTP Stats

Metrics reported by the remote peer about streams they are sending to you. Gives you insight into the sender's perspective.

Metric	What it tells you
packetsSent	Packets the remote has sent
bytesSent	Bytes the remote has sent
reportsSent	RTCP Sender Reports received
roundTripTime(ms)	RTT calculated from Sender Reports
totalRoundTripTime	Cumulative RTT for averaging
roundTripTimeMeasurements	Number of RTT measurements

ICE Candidate Pair Stats

Metrics for the network path between you and the remote peer. Covers bandwidth estimation, round-trip time, and packet flow at the transport level.

Bandwidth & Throughput

Metric	What it tells you
availableOutgoingBitrate	Estimated available bandwidth for sending
availableIncomingBitrate	Estimated available bandwidth for receiving
bytesSent	Total bytes sent on this pair
bytesReceived	Total bytes received on this pair
bytesDiscardedOnSend	Bytes dropped before sending

Connectivity

Metric	What it tells you
currentRoundTripTime(ms)	Latest measured RTT on this path
totalRoundTripTime	Cumulative RTT for averaging
responsesReceived	STUN connectivity check responses received
requestsSent	STUN connectivity check requests sent
requestsReceived	STUN connectivity check requests received
responsesReceived	Responses to STUN requests
responsesSent	Responses sent to STUN requests
consentRequestsSent	STUN consent freshness requests

Packet Flow

Metric	What it tells you
packetsSent	Total packets sent on this pair
packetsReceived	Total packets received on this pair
packetsDiscardedOnSend	Packets dropped before sending

Timestamps

Metric	What it tells you
lastPacketSentTimestamp	When the last packet was sent
lastPacketReceivedTimestamp	When the last packet was received

ICE Candidate Stats

Details about individual local and remote ICE candidates - the network addresses and paths available for the connection.

Local Candidate

Metric	What it tells you
address	Local IP address (may be redacted for privacy)
port	Local port number
protocol	Transport protocol (UDP/TCP)
candidateType	How the address was obtained (host/srflx/prflx/relay)
priority	ICE priority for pair ordering
url	STUN/TURN server URL used to gather this candidate
relayProtocol	Protocol used to reach the TURN server (udp/tcp/tls)

Remote Candidate

Metric	What it tells you
address	Remote peer's IP address
port	Remote peer's port number
protocol	Transport protocol (UDP/TCP)
candidateType	How the remote address was obtained

Transport Stats

Aggregate metrics at the DTLS/ICE transport layer - the encrypted tunnel that carries all media and data.

Bytes & Packets

Metric	What it tells you
bytesSent	Total bytes sent at the transport layer
bytesReceived	Total bytes received at the transport layer
packetsSent	Total packets sent at the transport layer
packetsReceived	Total packets received at the transport layer

Security

Metric	What it tells you
dtlsState	DTLS handshake state (new/connecting/connected/closed/failed)
dtlsCipher	Negotiated DTLS cipher suite
tlsVersion	TLS version used for DTLS
srtpCipher	SRTP cipher protecting the media

ICE State

Metric	What it tells you
iceState	ICE connectivity state
selectedCandidatePairId	Currently active candidate pair
selectedCandidatePairChanges	Number of path switches during the session

Codec Stats

Details about the audio and video codecs negotiated for each stream.

Metric	What it tells you
payloadType	RTP payload type number
mimeType	Codec identifier (e.g., video/VP8, audio/opus)
clockRate	Codec clock rate in Hz
channels	Audio channel count (mono/stereo)
sdpFmtpLine	Codec-specific SDP parameters

Media Source Stats

Metrics from the local media source before encoding - the raw camera/microphone input.

Audio Source

Metric	What it tells you
audioLevel	Current microphone audio level
totalAudioEnergy	Cumulative audio energy from the source
totalSamplesDuration	Duration of audio samples captured
echoReturnLoss	Echo cancellation effectiveness
echoReturnLossEnhancement	Additional echo suppression

Video Source

Metric	What it tells you
width	Camera capture width
height	Camera capture height
frames	Total frames from the camera
framesPerSecond	Current camera frame rate

Media Playout Stats

Metrics about audio playout to the speakers/headphones.

Metric	What it tells you
totalPlayoutDelay	Cumulative delay from jitter buffer to speaker
totalSamplesCount	Total samples played out
totalSamplesDuration	Total duration of played audio

Certificate Stats

Details about the DTLS certificates used to secure the connection.

Metric	What it tells you
fingerprint	Certificate fingerprint for DTLS verification
fingerprintAlgorithm	Hash algorithm used (typically sha-256)

Peer Connection Stats

Session-level metrics about the RTCPeerConnection itself.

Metric	What it tells you
dataChannelsOpened	Total data channels opened during the session
dataChannelsClosed	Total data channels closed during the session

Data Channel Stats

Metrics for individual RTCDataChannels - the non-media data pathway.

Metric	What it tells you
bytesSent	Bytes sent through this data channel
bytesReceived	Bytes received on this data channel
messagesSent	Messages sent
messagesReceived	Messages received

Calculated Metrics

rtcStats computes additional derived metrics that aren't in the raw getStats() output but are essential for understanding quality.

Bitrate (bits/s)

Metric	What it tells you
inbound-rtp.bytesReceived(bits/s)	Inbound media bitrate
outbound-rtp.bytesSent(bits/s)	Outbound media bitrate
candidate-pair.bytesSent(bits/s)	Transport-level send bitrate
candidate-pair.bytesReceived(bits/s)	Transport-level receive bitrate

Packet Loss

Metric	What it tells you
inbound-rtp.packetsLost(%)	Inbound packet loss percentage
remote-inbound-rtp.packetsLost(%)	Remote-side packet loss percentage

Latency

Metric	What it tells you
candidate-pair.totalRoundTripTime/responsesReceived	Average RTT
remote-inbound-rtp.totalRoundTripTime/roundTripTimeMeasurements	Average RTT from RTCP
inbound-rtp.jitterBufferDelay/jitterBufferEmittedCount(ms)	Average jitter buffer delay
media-playout.totalPlayoutDelay/totalSamplesCount(ms)	Average playout delay

MOS Score

Metric	What it tells you
MOS	Estimated Mean Opinion Score (1-5) for voice and quality

Frame & Sample Rates

Metric	What it tells you
inbound-rtp.framesDecoded(/s)	Decoded frame rate
inbound-rtp.framesReceived(/s)	Received frame rate
outbound-rtp.framesEncoded(/s)	Encoded frame rate
outbound-rtp.framesSent(/s)	Sent frame rate

Observations

Beyond raw metrics, rtcStats automatically detects 100+ behavioral patterns and anomalies - from symmetric NAT detection to CPU-limited encoding, from buffer bloat to echo feedback loops. Browse the full observations library.

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This reference covers all metrics defined in the W3C WebRTC Statistics API plus rtcStats calculated metrics. Each entry links to a detailed KB article with interpretation guidance, anomaly causes, and related metrics.

Built and maintained by rtcStats - WebRTC session quality, decoded.