If you’re using multiple CDNs or leveraging mid-stream switching in your video delivery — whether it’s to ensure coverage for the different regions you serve, provide reliability during high traffic events, or just have a fallback CDN if technical issues arise — you need reliable data to understand and measure the efficacy of your multi-CDN workflow.
That’s why we’re launching enhanced multi-CDN tracking in Mux Data to track each video CDN over the course of a video playback session. Now you can see which networks delivered your content and in what order. This unlocks better insights into CDN performance, more precise troubleshooting, and clearer understanding of how network switches impact viewer experience.
Introducing CDN Trace dimension
CDN Trace captures the sequential order of every CDN used during a view. If the CDN switches during playback, all CDN values will be registered in the CDN Trace dimension. Our existing CDN dimension gets an upgrade too. When CDN switches occur, it will now show the final CDN used in the view rather than 'multiple'.
For example, if a view starts on cdna and switches to cdnb during playback, you'll see:
- CDN: cdnb (last CDN value)
- CDN Trace: cdna > cdnb
The CDN Trace dimension is available as a filter and breakdown value in our Mux Data Metrics API. The CDN Trace dimension will is available in CSV and Streaming Exports for versions 14+
Flexible filtering options
CDN Trace comes with filtering capabilities to help you analyze CDN performance patterns, identify optimal switching scenarios, and troubleshoot issues that occur during specific network transitions.
- Includes: Find all views where a specific CDN was involved in video delivery at any point during playback. Filter for "includes cdna" to see every view that used cdna, whether it was the primary CDN or part of a switch.
- Excludes: Remove any views where the specified CDN is present.
- Matches: Find exact CDN transition patterns. Use "matches" 'cdna > cdnb' to identify all views that follow that exact CDN pattern.
CDN Change Events: See exactly when CDN changes occurred
We’re also launching a new CDN change event to help you pinpoint exactly when a CDN change occurs during a monitored view. CDN change events are created when CDNs are detected via response headers in all supported SDKs except Roku where CDN detection is not supported. CDN change events can be created manually in the Roku SDK since CDN detection is not supported.
CDN change events will be included in CSV and Streaming View Exports. CDN change events are supported in several web SDKs including video.js, hls.js, HTML5 video element, dash.js, and Shaka player. CDN change events are also supported in AVPlayer, AndroidX Media3, and Roku SDKs.
Enhanced Monitoring Stream
Our Monitoring Stream is being enhanced to report mid-stream CDN switches in Monitoring samples. When CDN switches occur during the 30-second sample window, a new previous_source option will be added to the monitoring sample output. The previous_source field will include both host_name and host_id for the previous CDN. The updated protobuf definition for the Monitoring Stream is available in the mux-protobuf repository.
[
{
"partitionID": 1,
"offset": 1,
"timestamp": 1752787090177,
"compression": "uncompressed",
"isTransactional": false,
"headers": [],
"key": {
"payload": "fc6b5d5e-6314-41df-9d76-46ae66ed2415",
"encoding": "text"
},
"value": {
"payload": {
"samples": [
{
"records": [
{
"duration": 20008,
"metrics": [
{
"type": "WATCH_DURATION_MS",
"value": 19958
}
],
"start": "2025-07-17T21:17:29Z"
}
],
"source": {
"hostname": "localhost:3000",
"host_id": "cdnb"
},
"view_id": "b795188d-7d4c-4c28-8880-46991a3f9b3e",
"ip": "24.xxx.xx.xxx",
"asn": 12271,
"viewer_os_family": "macOS",
"viewer_os_version": "10.15.7",
"player_name": "VideoJS HLS Player",
"viewer_device_category": "desktop",
"previous_source": {
"hostname": "localhost:3000",
"host_id": "cdna"
}
}
]
},
"encoding": "json"
}
}
]Start tracking your complete CDN data today
Ready to get deeper insights into your CDN performance? The new CDN Trace dimension and enhanced CDN tracking are now live for all Mux Data customers. If you use mid-stream CDN switching in your video stack, you’ll see these changes immediately. If you’re just getting started, check out our guide on how to set up automatic CDN detection at your CDN or configure your SDK integration to track in CDN metadata.
