HTTP 100 Continue vs 407 Proxy Authentication Required
HTTP 100 (Continue) is a 1xx Informational response, while 407 (Proxy Authentication Required) is a 4xx Client Error response. 100 indicates that the server has received the request headers and the client should proceed to send the request body. This lets the client know it can continue with the request or abort if the headers were rejected. In contrast, 407 means that the client must first authenticate itself with the proxy.
Description
The server has received the request headers and the client should proceed to send the request body. This lets the client know it can continue with the request or abort if the headers were rejected.
When You See It
When a client sends an Expect: 100-continue header, the server responds with 100 before the client sends the body.
How to Fix
This is an interim response — no fix needed. The client should continue sending the request body.
Description
The client must first authenticate itself with the proxy.
When You See It
When accessing the internet through a corporate proxy that requires authentication.
How to Fix
Configure proxy credentials in your HTTP client or browser settings.
Key Differences
100 is a 1xx Informational response, while 407 is a 4xx Client Error response.
HTTP 100: The server has received the request headers and the client should proceed to send the request body. This lets the client know it can continue with the request or abort if the headers were rejected.
HTTP 407: The client must first authenticate itself with the proxy.
You encounter 100 when when a client sends an Expect: 100-continue header, the server responds with 100 before the client sends the body.
You encounter 407 when when accessing the internet through a corporate proxy that requires authentication.
When to Use Which
For 100 (Continue): This is an interim response — no fix needed. The client should continue sending the request body. For 407 (Proxy Authentication Required): Configure proxy credentials in your HTTP client or browser settings.