Fixes / Zoom · Checked September 30, 2026

Zoom error code 104103: what it means and how to fix it

Short answer

Zoom error code 104103 means the Zoom app could not connect to Zoom's servers. Most of the time a firewall, antivirus program, VPN or proxy is blocking the connection, not a fault in the app. First try a different network, such as a phone hotspot. If Zoom works there, allow Zoom through your firewall and antivirus, or ask your network admin to open Zoom's ports.

What this message means

Zoom says error 104103 means "an issue is preventing a connection between your device and Zoom's servers." It belongs to a group of connection errors (104101 to 104125) that all mean the same thing: the app started, but its connection to Zoom's servers was blocked or timed out. Web pages can still load normally, because Zoom also needs TCP ports 8801 and 8802 and UDP ports 3478, 3479 and 8801 to 8810, which ordinary browsing never uses. So the cause is almost always something between your computer and Zoom, such as a firewall, antivirus, VPN, proxy, or a school or office network filter. The Zoom app itself is rarely the problem.

Common causes

Cause	How to tell
A school, office or public Wi-Fi network (hotel, café, airport) blocks the ports or domains Zoom needs	The error appears on one network but not on another. Zoom connects fine over a phone hotspot or at home, and websites still load normally on the network that fails.
Antivirus or security software is blocking Zoom's connection (Zoom names this as a known cause, for example AVG)	The error started after you installed or updated a security program, and Zoom connects within a minute of turning that program's web or firewall protection off.
A VPN or proxy is sending Zoom traffic through a route that drops it or inspects it with SSL inspection	Zoom connects when you disconnect the VPN. On a work computer, the error only happens while you are connected to the company network or VPN.
Windows Defender Firewall or the macOS firewall is blocking the Zoom app	Zoom is missing or unchecked in the Windows "Allowed apps" list, or macOS Firewall Options is set to "Block all incoming connections" or lists Zoom as blocked.
A router or DNS problem on your own connection, or a regional block by your internet provider	Other devices on the same Wi-Fi also cannot join Zoom, and the error goes away after you restart the router or switch to mobile data.
A Zoom service outage (rare)	status.zoom.us shows an incident for Meetings, and people on other networks get the same error at the same time.

How to fix it

1. Test on another network to find out where the block is

Quit Zoom completely. On Windows, right-click the Zoom icon in the taskbar notification area and choose Exit. On Mac, press Cmd+Q while Zoom is the active app.
Turn off any VPN you have running.
Connect the computer to a different network, such as a phone hotspot.
Open Zoom again and join the meeting.
If it works, your usual network (or its firewall) is the cause, so go to the firewall or network admin fix below. If it still fails, the block is on your computer, so continue with the next fix.
Also check status.zoom.us to rule out a Zoom outage.

2. Temporarily turn off antivirus and allow Zoom through it

Open your antivirus or internet security program (for example Norton, McAfee, AVG, Avast, Bitdefender or ESET).
Turn off its firewall or web protection for 10 to 15 minutes.
Restart Zoom and try the meeting again.
If Zoom connects, turn protection back on and add the Zoom app (Zoom.exe on Windows, zoom.us.app on Mac) to the program's exceptions or trusted list.
If the program has a URL or HTTPS scanning exclusion list, add zoom.us and *.zoom.us so Zoom's traffic is not inspected.

3. Allow Zoom through the Windows or macOS firewall

Windows 10 and 11; macOS 13 Ventura and later (older macOS uses System Preferences > Security & Privacy > Firewall)

Windows: open Windows Security > Firewall & network protection > Allow an app through firewall.
Click Change settings, find Zoom (or Zoom Workplace), and tick both Private and Public. If Zoom isn't in the list, click Allow another app and browse to Zoom.exe.
Mac: open System Settings > Network > Firewall, then click Options.
Make sure "Block all incoming connections" is off and that Zoom is set to "Allow incoming connections."
Restart Zoom and join again.

4. Restart the router and clear the DNS cache

Unplug the modem and router, wait 30 seconds, and plug them back in.
Windows: open Command Prompt and run ipconfig /flushdns.
Mac: open Terminal and run sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder, then type your Mac password when asked.
Restart Zoom and try again.

5. Ask the network admin to open Zoom's required ports and domains

Office, school or managed networks with a firewall or proxy

Send your IT team the Zoom article "Zoom network firewall or proxy server settings".
Ask them to allow the domains *.zoom.us and *.zoom.com.
Ask them to allow outbound TCP 80 and 443, TCP 443, 8801 and 8802, and UDP 443, 3478, 3479 and 8801 to 8810 to Zoom's IP ranges.
Ask them to exclude zoom.us and *.zoom.us from proxy SSL inspection, as Zoom recommends.
Until that's done, join from a phone on mobile data, or use the "Join from your browser" link on the meeting launch page.

6. Update or reinstall Zoom

In the Zoom desktop app, click your profile picture (top right) and choose Check for Updates. Install any update.
If the error continues, uninstall Zoom. On Windows, use Settings > Apps > Installed apps. On Mac, open Zoom, click zoom.us in the menu bar and choose Uninstall Zoom.
Download the current installer from zoom.us/download and install it.
Sign in and join the meeting again.

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Still not fixed?

If Zoom works on another network but not yours, the block is on that network. Ask your IT department (at work or school) or your internet provider to check whether they can reach Zoom, and give them Zoom's firewall and proxy article. If Zoom fails on every network and every device, check status.zoom.us for an outage. If there is none, contact Zoom Support at support.zoom.com. Tell them the error code and whether you use a VPN, proxy or security software, and attach your Zoom logs if they ask for them. Until it's fixed, you can join the meeting from the Zoom phone app on mobile data or with the "Join from your browser" link.

Questions people ask

Is Zoom error 104103 caused by my internet being down?

Usually not. Web pages often keep loading normally, because Zoom needs extra ports (8801 to 8810, 3478 and 3479) that a firewall, VPN or network filter can block while regular browsing still works.

What's the difference between Zoom errors 104101, 104103 and 104114?

They are in the same 104101 to 104125 group, and they all mean the Zoom app couldn't reach Zoom's servers. The fixes are the same: check the firewall, antivirus, proxy or VPN, and your internet provider.

Why does Zoom work on my phone but show 104103 on my laptop?

The phone is probably on mobile data, or it doesn't have the laptop's VPN, antivirus or firewall. Connect the laptop to the phone's hotspot. If Zoom works there, the network or the laptop's security software is the cause.

Can I join the meeting while error 104103 is happening?

Often, yes. The "Join from your browser" link on the meeting launch page or the Zoom mobile app on cellular data can get you in, because they take a different network path.

Will reinstalling Zoom fix error 104103?

Only occasionally. Zoom describes 104103 as a connection problem, so reinstalling helps only when the app is outdated or damaged. Check the network and security software first.

Sources

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