Outbound Proxy (Mux, XUDP)

Outbound connections are used to send data. For available protocols, please see Outbound Protocols.

OutboundObject

OutboundObject corresponds to a sub-element of the outbounds item in the configuration file.

TIP

The first element in the list serves as the primary outbound. When a routing match does not exist or fails, traffic is sent via the primary outbound.

{
  "outbounds": [
    {
      "sendThrough": "0.0.0.0",
      "protocol": "protocol_name",
      "settings": {},
      "tag": "identifier",
      "streamSettings": {},
      "proxySettings": {
        "tag": "another-outbound-tag",
        "transportLayer": false
      },
      "mux": {},
      "targetStrategy": "AsIs"
    }
  ]
}

sendThrough: address

The IP address used to send data. This is effective when the host has multiple IP addresses. The default value is "0.0.0.0".

You can enter an IPv6 CIDR block (e.g., 114:514:1919:810::/64), and Xray will use a random IP address from the address block to initiate external connections. You need to correctly configure the network access method, routing table, and kernel parameters to allow Xray to bind to any IP within the address block.

For networks using NDP access, it is not recommended to set a subnet smaller than /120. Otherwise, it may cause issues such as NDP flooding, leading to the router's neighbor cache becoming full.

Special value origin: If this value is used, the request will be sent using the IP address of the local machine that received the connection.

For example, if the machine has a full IPv4 range 11.4.5.0/24 and listens on 0.0.0.0 (all IPv4 and IPv6 on the network interface), if a client connects to the local machine via 11.4.5.14, the outbound request will also be sent via 11.4.5.14. If the client connects via 11.4.5.10, the outbound request will be sent via 11.4.5.10. This also applies to cases where the machine has a full range/multiple IPv6 addresses.

As mentioned in the inbound introduction, because of the connectionless nature of UDP, Xray cannot know the original destination IP where the request entered the core (for example, in the same QUIC connection, it might even change), so this feature cannot take effect for UDP.

protocol: "blackhole" | "dns" | "freedom" | "http" | "loopback" | "shadowsocks" | "socks" | "trojan" | "vless" | "vmess" | "wireguard"

The connection protocol name. For the list of optional protocols, see Outbound Protocols on the left.

settings: OutboundConfigurationObject

Specific configuration content, which varies by protocol. See OutboundConfigurationObject in each protocol for details.

tag: string

The identifier for this outbound connection, used to locate this connection in other configurations.

DANGER

When not empty, its value must be unique among all tags.

streamSettings: StreamSettingsObject

The underlying transport method is the way the current Xray node connects with other nodes.

proxySettings: ProxySettingsObject

Outbound proxy configuration.

mux: MuxObject

Specific configuration related to Mux.

targetStrategy: "AsIs" | "UseIP" | "UseIPv6v4" | "UseIPv6" | "UseIPv4v6" | "UseIPv4" | "ForceIP" | "ForceIPv6v4" | "ForceIPv6" | "ForceIPv4v6" | "ForceIPv4"

If this outbound attempts to send a domain request, this controls whether it is resolved/how it is resolved to an IP before sending.

The default value is AsIs, meaning it is sent to the remote server as is. All parameter meanings are roughly equivalent to domainStrategy in sockopt.

TIP

This controls proxied requests. If the address of the outbound proxy server is a domain name, and you need to select a resolution strategy for the domain name itself, you should configure domainStrategy in sockopt.

ProxySettingsObject

{
  "tag": "another-outbound-tag",
  "transportLayer": false
}

tag: string

When the identifier of another outbound is specified, data sent by this outbound will be forwarded to the specified outbound for transmission.

DANGER

This option conflicts with SockOpt.dialerProxy. Choose one as needed.

By default, this forwarding method does not go through the underlying transport method (REALITY/XHTTP/gRPC...), meaning the streamSettings of this outbound will not take effect.
If you need forwarding that supports underlying transport methods, please use SockOpt.dialerProxy instead or set transportLayer to true.

transportLayer: true | false

true converts this setting to SockOpt.dialerProxy to support forwarding via underlying transport methods. The default is false, meaning no conversion.

MuxObject

The Mux function distributes data from multiple TCP connections over a single TCP connection. For implementation details, see Mux.Cool. Mux is designed to reduce TCP handshake latency, not to increase connection throughput. Using Mux for watching videos, downloading, or speed testing usually has a negative effect. Mux only needs to be enabled on the client side; the server side adapts automatically. The second use of Mux is to distribute multiple UDP connections, i.e., XUDP.

MuxObject corresponds to the mux item in OutboundObject.

{
  "enabled": true,
  "concurrency": 8,
  "xudpConcurrency": 16,
  "xudpProxyUDP443": "reject"
}

enabled: true | false

Whether to enable Mux for forwarding requests. Default is false.

concurrency: number

Maximum concurrent connections. Minimum 1, maximum 128. If omitted or set to 0, it equals 8. Values greater than 128 are treated as 128, because once a connection reaches the maximum reuse count of 128, it will no longer be assigned any new sub-connections.

This value represents the maximum number of sub-connections carried on a single TCP connection. For example, if concurrency=8 is set, when the client issues 8 TCP requests, Xray will only issue one actual TCP connection, and all 8 requests from the client are transmitted over this TCP connection.

When the maximum sub-connection capacity of all Mux connections is fully occupied, the core will initiate new connections to carry sub-connections. If a large number of sub-connections are concurrent in a short time and subsequently decrease, the internal scheduler of the core will tend to distribute requests to 2 connections alternately and leave other connections idle, waiting for all their sub-connections to end naturally before closing them to save resources. If the total number of sub-connections continues to be lower than concurrency for a long time, after one of the connections reaches the maximum reuse count, the core will revert to a single connection state.

TIP

When set to a negative number, such as -1, the Mux module is not used to carry TCP traffic.

xudpConcurrency: number

Use a new XUDP aggregation tunnel (i.e., another Mux connection) to proxy UDP traffic. Fill in the maximum number of concurrent sub-UoT. Minimum 1, maximum 1024. If omitted or set to 0, it will follow the same path as TCP traffic, which is the traditional behavior.

TIP

When set to a negative number, such as -1, the Mux module is not used to carry UDP traffic. The proxy protocol's original UDP transmission method will be used. For example, Shadowsocks will use native UDP, and VLESS will use UoT.

xudpProxyUDP443: string

Controls how Mux handles proxied UDP/443 (QUIC) traffic:

• Default reject: Rejects traffic (browsers typically fall back to TCP HTTP2 automatically).
• allow: Allows traffic to go through the Mux connection.
• skip: Does not use the Mux module to carry UDP 443 traffic. The proxy protocol's original UDP transmission method will be used. For example, Shadowsocks will use native UDP, and VLESS will use UoT.