# Pre-match - sing-box
The universal proxy platform.
Author: nekohasekai

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# Pre-match

Changes in sing-box 1.13.0

bypass

Pre-match is rule matching that runs before the connection is established.

### How it works

When TUN receives a connection request, the connection has not yet been established, so no connection data can be read. In this phase, sing-box runs the routing rules in pre-match mode.

Since connection data is unavailable, only actions that do not require connection data can be executed. When a rule matches an action that requires an established connection, pre-match stops at that rule.

### Supported actions

#### reject

Reject with TCP RST / ICMP unreachable.

See reject for details.

#### route

Route ICMP connections to the specified outbound for direct reply.

See route for details.

#### bypass

Since sing-box 1.13.0

Only supported on Linux with `auto_redirect` enabled.

Bypass sing-box and connect directly at kernel level.

If `outbound` is not specified, the rule only matches in pre-match from auto redirect, and will be skipped in other contexts.

For all other contexts, bypass with `outbound` behaves like `route` action.

See bypass for details.