Short answer: A browser-based IPv6 test can show whether this browser can reach IPv6 test endpoints while your VPN is connected, and may show the address or network that those endpoints observe. It cannot prove that every app, browser profile, or future connection uses the VPN. This site does not scan your traffic or run an IPv6 leak test.

What an IPv6 check is looking for

IPv6 is a separate IP protocol with 128-bit addresses, defined by the IETF's IPv6 specification. A device or network may have working IPv4, IPv6, both, or neither for a particular connection. VPN products also differ: a client may route IPv6 through a supported VPN server, block IPv6, or handle it differently by platform and configuration. Proton's current IPv6 support notes are one provider-specific example; do not assume another provider behaves the same way.

Run a cautious browser comparison

1. Use a device and network you control. Note the VPN app, platform, selected server, and any IPv6 or leak-protection setting that the provider documents. Do not change protection settings just to make a test pass.
2. With the VPN connected, open a browser IPv6 test such as test-ipv6.com. Review whether its IPv6 connectivity tests succeed and what network information it reports. The test instructs your browser to request test URLs; the destination necessarily receives connection information such as the source IP used for that request.
3. If it is safe for your situation, repeat the same test with the VPN disconnected, then reconnect and repeat once. Compare the results in the same browser, on the same network, without changing other settings. Avoid posting screenshots or copied results publicly: they may contain your IP address or network details.
4. Check your VPN provider's current documentation for what a passing result should look like on your exact app, platform, server, and configuration. Ask provider support if the result conflicts with its documented behavior.

How to interpret the result

• No IPv6 connectivity while connected means those browser test endpoints did not complete an IPv6 connection in that run. Some VPNs intentionally block IPv6; this alone does not prove the VPN is broken or that IPv6 is blocked in every app.
• An IPv6 connection succeeds while connected shows that the browser reached the test over IPv6. It does not by itself establish whether the address belongs to a VPN exit, whether the provider intended IPv6 support, or what unrelated apps do. Compare it with provider documentation and the disconnected result.
• The same address appears in both runs is a reason to investigate, not conclusive proof of a leak. Test sites, browser settings, network changes, relays, and provider behavior can affect what is observed.
• A failed or inconsistent test can reflect the network, browser extensions, content blocking, temporary reachability, or test configuration. A single browser result does not diagnose the whole device.

What this browser check cannot prove

The test covers requests made by that browser at that time. It does not inspect other apps, every browser profile, background traffic, DNS behavior, or connections made after a network or VPN setting changes. It is not a security audit, and it cannot certify anonymity or guarantee that a VPN always routes all traffic correctly.

For address syntax only, use this site's IPv6 validator; it does not connect to the network. For a broader view of ISP, Wi-Fi, VPN, resolver, and website visibility, see the VPN visibility matrix and visibility guide. For IPv4-versus-IPv6 address context, read the public, private, and CGNAT IPv4 guide.

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