diff --git a/README.md b/README.md
index ac4f932..cde5553 100644
--- a/README.md
+++ b/README.md
@@ -130,6 +130,7 @@ Proxy Server: AWS US West Oregon (us-west-2)
       "password": "yubiyubi"
     }
   },
+  "prometheus_listen": ":8080", // Prometheus HTTP metrics server listen address (at /metrics)
   "recv_window_conn": 33554432, // QUIC stream receive window
   "recv_window_client": 67108864, // QUIC connection receive window
   "max_conn_client": 4096 // Max concurrent connections per client
@@ -172,6 +173,21 @@ The endpoint must return results with HTTP status code 200 (even if the authenti
 }
 ```
 
+#### Prometheus Metrics
+
+You can make Hysteria expose a Prometheus HTTP client endpoint for monitoring traffic usage with `prometheus_listen`.
+If configured on port 8080, the endpoint would be at `http://example.com:8080/metrics`.
+
+```text
+hysteria_traffic_downlink_bytes_total{auth="55m95auW5oCq"} 122639
+hysteria_traffic_downlink_bytes_total{auth="aGFja2VyISE="} 3.225058e+06
+
+hysteria_traffic_uplink_bytes_total{auth="55m95auW5oCq"} 40710
+hysteria_traffic_uplink_bytes_total{auth="aGFja2VyISE="} 37452
+```
+
+`auth` is the auth payload sent by the clients, encoded in Base64.
+
 ### Client
 
 ```json5
diff --git a/README.zh.md b/README.zh.md
index 1ba74a6..198ed29 100644
--- a/README.zh.md
+++ b/README.zh.md
@@ -160,6 +160,21 @@ Hysteria 是专门针对恶劣网络环境（常见于卫星网络、在中国
 }
 ```
 
+#### Prometheus 流量统计
+
+通过 `prometheus_listen` 选项可以让 Hysteria 暴露一个 Prometheus HTTP 客户端 endpoint 用来统计流量使用情况。
+例如如果配置在 8080 端口，则 API 地址是 `http://example.com:8080/metrics`
+
+```text
+hysteria_traffic_downlink_bytes_total{auth="55m95auW5oCq"} 122639
+hysteria_traffic_downlink_bytes_total{auth="aGFja2VyISE="} 3.225058e+06
+
+hysteria_traffic_uplink_bytes_total{auth="55m95auW5oCq"} 40710
+hysteria_traffic_uplink_bytes_total{auth="aGFja2VyISE="} 37452
+```
+
+`auth` 是客户端发来的验证密钥，经过 Base64 编码。
+
 ### 客户端
 
 ```json5