Zwift Live ANT+ Log Viewer

Drop Zwift log here.

You can use the log of an in progress ride and it will auto-update.


Only tested in Chrome and Firefox.

Avg. fails

This is the average rx fails of a device. It is calculated across the whole time of the log so if you pair or unpair a device mid-ride its average will be affected.

Channel 0 in wrong state

I'm not entirely sure what this means but I think it might have something to do with background searching having to be restarted. This could mean that it takes longer to find and pair devices.

Data rate

Most ANT+ devices transmit at 4Hz but some have the option to transmit at 8Hz. There's no good way to tell the difference in the Zwift log so we have to guess from the number of rx fails seen per second. The problem with this method is if an 8Hz device has a very good signal strength it will appear as 4Hz and have double the rx fails percentage it should have.

Heart rate, speed, and cadence devices are always 4Hz. Speed + cadence devices are always 8Hz. Power meters can be 4Hz or 8Hz but most seem to be 8Hz. Trainers seem to be a mix of 4Hz and 8Hz. If you see "[PowerMeter]" lines in your Zwift log then the device which is sending those is 8Hz.

Devices paired

A device was paired. If this appears outside of the Zwift pairing screen then it probably indicates a problem.

Devices unpaired

A device was unpaired. If this appears outside of the Zwift pairing screen then it probably indicates a problem.

Rx fails

An rx fail is when a page from an ANT+ device arrives later than expected and officially is caused only by interference. However I suspect it might also be made worse by slow processors and firmware in most trainers and power meters failing to keep up.

When there are two seconds of solid rx fails (i.e. 8 straight rx fails at 4Hz or 16 at 8Hz) a drop out occurs. Unfortunately the Zwift logs aren't accurate enough to determine exactly when this happens.

Since we can't determine exact signal quality and the fails are grouped into 10 second bins then the colours are actually pretty arbitrary. Green is 39% and under, orange is 40% to 65%, and red is 66% and above. They were chosen based on my experience of when drop outs start to occur with green being no drop outs, orange being possible drop outs, and red being almost certain drop outs.

It seems to be normal for trainers and power meters to have 2-5x the rx fails of heart rate and cadence devices.

Sometimes even different ANT+ profiles broadcasted by the same device have different failure rates (this is why I suspect processors/firmware are partly responsible as well).

If you see no rx fails but you are getting sensor readings then your environment is very very good. If you see no rx fails and you're not getting sensor readings then the device isn't connected.

Starting ANT+ search

Zwift started a search for new devices. If this appears outside of the Zwift pairing screen then it probably indicates a problem. If you use the pairing screen as a brake in Zwift then you might see a few of these mid-ride.

Stopping ANT+ search

Zwift should follow every started search with a stopped search but sometimes gets itself into a buggy state where it spams stopped search and never starts new searches. If that happens then you will need to keep replugging the USB dongle or restart Zwift. Even though this is orange on the graph if you see it getting spammed hundreds of times then it's equivalent to "USB dongle failed".

Too many rx fails

This is a drop out after two seconds of solid rx fails. It may or may not align with an increase in rx fails on one of the device graphs.

In a healthy environment devices will often reconnect immediately and you won't even notice a drop out in Zwift. If you get drop outs and lose sensor readings in game then try cleaning up your environment or getting an ANTUSB-m (Dynastream, Garmin, or Zwift branded) dongle which supports High Duty Search and can pair much quicker. Keep the extension cable <=2 metres and buy a good brand like Lindy (in my experience all 3 metre cables made things no better or worse and Amazon Basics branded cables made no difference).

These also appear when a device has been idle for too long and in those cases is completely normal.

USB dongle failed

Something is wrong with the USB dongle. Zwift will see the dongle but won't be able to find any devices. Sometimes replugging it will fix the issue but other times you have to restart Zwift.

USB dongle not found

You started Zwift without the dongle plugged in. This is only displayed so that something shows up for Bluetooth logs instead of a confusing blank graph.

USB dongle plugged in

There should be only one of these at the start. If you see more then you might have a loose connection or an underpowered USB port.