01

What the switch controls

The IPv6 switch in Clash settings decides whether the core handles IPv6 traffic and resolves AAAA records. With it off the core drops IPv6 connections and the system falls back to IPv4, which is more predictable for most people.

The situations that genuinely need it are narrow: your nodes only offer IPv6 addresses, you need to reach IPv6-only resources, or an application explicitly requires a direct IPv6 connection. Outside those cases, leaving it off is a reasonable default.

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02

Three things to check when enabling it

  1. 1

    Enable and reload

    Turn IPv6 on in Clash settings and save. The core reloads its configuration automatically.

  2. 2

    Make sure DNS returns AAAA

    Many configs block AAAA queries while IPv6 is disabled. After enabling the switch, go back to the dns section and confirm AAAA is not being filtered out, otherwise you still never receive an IPv6 address.

  3. 3

    Check the TUN adapter if you use it

    In your network adapter properties, confirm IPv6 is enabled on the TUN adapter. If the adapter has no IPv6 address it cannot carry that traffic.

03

Testing and backing out

Open an IPv6 test page and check both reachability and which exit address it reports. If some sites become slower or stop loading after you enable IPv6, the likely causes are a poor IPv6 path on the node or DNS returning an unreachable AAAA record, leaving the system to wait for a timeout before falling back. Turning the switch off again is the fastest cure.

  • Intermittent slowness is a classic IPv6 fallback symptom
  • Disabling IPv6 does not affect IPv4 nodes in any way
  • Flush the browser DNS cache before retesting
04

Common questions

IPv6 is on but the test site still reports IPv4 only.

Then your connection or your node has no IPv6 available. The switch permits the core to handle IPv6; it cannot create a path that does not exist.

Could leaving IPv6 off cause a leak instead?

It can. If the core ignores IPv6 while the system has native IPv6, some applications will simply go out over IPv6 directly. Pick one of two consistent setups: disable IPv6 in the client so the core drops it, or enable TUN so the virtual adapter carries IPv6 as well.