Edit Captive Portal Check

So 9. Feb 2025, 14:45

The Captive Portal Check on Android devices verifies whether a Wi-Fi network has an internet connection or requires a login portal (e.g., in hotels or cafés). Upon connecting, Android sends a request to a server (by default, http://connectivitycheck.volla.tech). If the server returns a specific response (HTTP 204), Android recognizes a direct internet connection. If redirected to a login page instead, Android opens it in the browser so the user can log in. This ensures the system confirms you are actually online or can log in.
It’s like an automatic test to check if the Wi-Fi connects directly to the internet or if you need to log in on a webpage first.

The Captive Portal Check can affect your home Wi-Fi or mobile data connection if the default server is temporarily unreachable

Home Wi-Fi:
Android checks whether the Wi-Fi has internet access upon connection. If the server doesn’t respond, Android might mistakenly assume there’s no internet connection and display a warning symbol (e.g., “!”). In some cases, if “Automatic Switch” is enabled, the device may switch to mobile data even though the Wi-Fi is functional. The connection often remains usable, as the check only affects the display.

Mobile Data:
The check has less impact here, as mobile data is usually directly connected to the internet. However, an unreachable server could cause Android to mark the connection as limited, which might, in rare cases, disrupt the use of certain apps.

Simply put:
If the test server doesn’t respond, your phone might think your Wi-Fi or mobile data isn’t working, even if it is. You can usually keep browsing, but you might see annoying warnings or the phone might switch to mobile data.

Does the use of a VPN have an impact on the issue?

The use of a VPN can, under certain circumstances, have a problem-solving impact on the temporary unavailability of the Connectivity Test Server on Android devices, but it is not a guarantee and depends on the cause of the issue. Here is a concise analysis:
Possible positive effects of a VPN:
Bypassing network restrictions:
A VPN can help if the Connectivity Test Server (e.g., connectivitycheck.gstatic.com) is unreachable due to local network restrictions, firewalls, or ISP blocks (e.g., in restrictive countries), as traffic is routed through a different server.

Encryption and routing through a VPN server can circumvent such blocks.

Stable connection in unreliable networks:
In unstable or heavily monitored networks (e.g., public Wi-Fi), a VPN can stabilize the connection by tunneling traffic through a reliable server.

Switching to a different VPN server or protocol (e.g., OpenVPN instead of WireGuard) can reduce connection drops.

Bypassing DNS issues:
If the Connectivity Test Server is unreachable due to faulty ISP DNS settings, a VPN with its own DNS servers (e.g., VPN-specific DNS instead of ISP DNS) can resolve the issue.

Limitations and potential issues:
VPN as a cause of connectivity issues:
An unstable VPN server or incorrect settings (e.g., blocked ports, wrong protocol) can itself cause connectivity issues, including the unavailability of the Test Server.

Android sometimes sends connectivity checks outside the VPN tunnel, which, according to Google, is intentional but can affect reachability.

Server dependency:
If the Connectivity Test Server itself is down (e.g., Google server issues), a VPN won’t help, as the issue is not network-related.

Performance drawbacks:
A VPN can slow down the connection or cause instability, especially with high encryption (e.g., AES 256-bit). Switching to lower encryption (e.g., AES 128-bit) or a different server may help.

Practical steps:
Test different VPN servers: Switch to a server in another country to bypass local blocks.

Switch protocols: Use OpenVPN or Lightway (if available) for unstable networks.

Check DNS settings: Use VPN-specific DNS servers or public ones like Google DNS (8.8.8.8).

Disable VPN: Test if the issue persists without a VPN to rule out the VPN service as the cause.

Check Always-On VPN: Ensure Android’s Always-On VPN is properly configured for automatic connections.

Conclusion:
A VPN can resolve the unavailability of the Connectivity Test Server if the issue is caused by network restrictions, DNS errors, or unstable connections. However, it is not a universal solution, as VPNs can also cause issues. Test different servers, protocols, and settings to find the optimal configuration. If the problem persists, it may be due to the server itself or other device settings.

Thanks to:
@Silver
and our diligent Marcus and Rüdiger from our Telegram Community
for the guides already written in posts/PDFs, which I slightly adapted.

If the Captive Portal Check fails (i.e., the Captive Portal Check Server defined in VollaOS is unreachable), there are two ways to fix this issue:

Option 1: Using a PC and the terminal.
Option 2: Using apps from the F-Droid store.

Option 1

Requirements
PC and phone are connected via a data cable.

Admin rights on the PC.

Developer settings, including USB Debugging, are enabled on the phone.

Steps
Set up ADB Tools on the PC

a) Windows: Install ADB on the PC
This article was very helpful: https://www.nextpit.de/adb-treiber-android-windows
Download the Platform Tools to the PC (e.g., for Windows: https://dl.google.com/android/repositor ... indows.zip).

Extract the Platform Tools zip file somewhere, e.g., to C:.

Optional: Test ADB by opening the “adb.exe” file in the Platform Tools folder with Shift + right-click in the terminal and running the adb command. This lists all available ADB commands and other details.
IMPORTANT: In Windows, the command must be .\adb, as Windows will otherwise look elsewhere.

b) Linux: ADB Tools should already be preinstalled.
If not, run in the terminal: