A VPN can make video calls lag, because it sends your audio and video through an extra server before they reach the meeting service. How much depends on where that server is, how busy it is and how the tunnel carries traffic. To find out on your connection, run the same check with the VPN on and off. If the VPN belongs to your employer, keep it on and ask IT about split tunnelling.
The guide to calls that lag on fast internet explains latency, jitter and throughput. This one deals only with what a VPN changes and how to measure it.
Where a VPN adds delay
Microsoft’s Teams network guidance recommends a path for Teams traffic that bypasses the VPN and lists the reasons. Zoom’s network configuration guide warns of significant audio and video degradation when meeting media goes through a VPN. Between them, the causes are:
| Cause | What happens | What you notice |
|---|---|---|
| A longer route | Traffic travels to the VPN server first. Microsoft notes it may then reach a Teams entry point further from you. | Higher latency: people talk over each other |
| A busy VPN server | Calls from many remote workers share the same VPN equipment. Zoom warns that meeting media puts a heavy load on it. | Jitter and frozen video at busy times |
| No UDP in the tunnel | Teams needs UDP for media, and Microsoft notes that some VPNs do not support it. Zoom says falling back to TCP adds overhead that can hurt audio and video. | Choppy or delayed audio |
| Double encryption | Microsoft points out that a VPN encrypts media that the meeting service already encrypts. | Extra processing for every packet of the call |
The same applies to personal VPN apps. OpenVPN, for example, uses UDP for performance and offers TCP mainly for networks that block UDP. A server on another continent adds round-trip time to every packet in a call.
Compare the same check with the VPN on and off
One measurement tells you little. Two measurements a minute apart, on the same PC and network, show what the VPN changes.
- Sit where you will take the call, on the same Wi-Fi band or cable. Pause cloud sync and large downloads.
- Connect the VPN and run a connection check. Write down latency, jitter and upload.
- If you are allowed to, disconnect the VPN and run the same check straight away. Write down the same numbers.
- Repeat both runs once more. A single slow result can be a coincidence.
- Confirm in the meeting app itself. The guide to Teams test calls and Zoom test meetings shows where to find them.
| With the VPN on | Likely cause | Next step |
|---|---|---|
| Latency much higher, jitter similar | A distant VPN server | Choose a server location closer to you, if you can |
| Jitter higher, especially at busy hours | A loaded VPN server or a TCP-based tunnel | Try another server or protocol in a personal VPN; report it to IT for a work VPN |
| Upload much lower | The VPN limits throughput | Same as above; compare at another time of day |
| Little difference | The VPN is not the main problem | Look at Wi-Fi, upload and other devices, as in the pre-call internet check |
What CallReady measures with a VPN connected
CallReady runs its connection check from your PC. It times a series of small web requests to Cloudflare’s speed-test service and runs a short, capped download and upload, then shows latency, jitter and throughput next to the camera and microphone results. Those requests leave the PC like ordinary web traffic, so when the VPN carries your web traffic, the result includes the VPN; when it is disconnected, it does not.
Know its limits before you act on the numbers:
- It measures the route to Cloudflare over HTTPS, not the media path to a Teams or Zoom server.
- It does not measure packet loss.
- If IT has set up split tunnelling, your meeting app may bypass the VPN while CallReady’s requests still go through it. A poor VPN-on result then describes the VPN, not your calls. Use the meeting app’s own test for those.
For a personal VPN: try a nearer server
If you use a VPN app for privacy or on public Wi-Fi, choose a server location near you, reconnect and run the check again. If the app lets you choose a protocol, compare a UDP-based option with the one you use now. Pick the setup with the lowest jitter, not the highest download speed.
Disconnecting for a call is a trade-off only you can make. On a network you do not trust, such as hotel or café Wi-Fi, the VPN protects the rest of your traffic. Keep it on there and accept a slower call, or move to a network you trust.
For a work VPN: ask IT about split tunnelling
Do not disconnect a VPN your employer requires. Split tunnelling is the documented fix: call traffic goes directly to the meeting service while everything else stays in the VPN. Microsoft recommends it for Teams and says bypassing the VPN improves Teams quality. Zoom recommends split tunnelling for UDP ports 8801 to 8810 and TCP 443 to its own servers.
Give IT something specific: which meeting app you use, whether you join from the desktop app or a browser, when the lag happens, and your latency and jitter with the VPN on and, if you were allowed to test it, off. Microsoft notes that split tunnelling for Teams in a browser has caveats, so the browser detail matters.
Online proctored exams have their own rules. Pearson VUE lists VPNs among prohibited technology for OnVUE exams; read your exam’s rules before test day. The proctored exam tech check covers the rest of the setup.
Frequently asked questions
Does a VPN always make video calls worse?
Should I turn off my work VPN before a call?
Does CallReady’s connection check go through my VPN?
Can I use a VPN during an online proctored exam?
Run CallReady’s check with the VPN on and off, then confirm the result in your meeting app’s own test.
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