HTTP 100 Continue vs 406 Not Acceptable
HTTP 100 (Continue) is a 1xx Informational response, while 406 (Not Acceptable) 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, 406 means that the server cannot produce a response matching the Accept headers sent by the client.
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 server cannot produce a response matching the Accept headers sent by the client.
When You See It
When requesting a content type the server doesn't support (e.g., Accept: application/xml when only JSON is available).
How to Fix
Adjust the Accept header to a format the server supports.
Key Differences
100 is a 1xx Informational response, while 406 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 406: The server cannot produce a response matching the Accept headers sent by the client.
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 406 when when requesting a content type the server doesn't support (e.g., Accept: application/xml when only JSON is available).
When to Use Which
For 100 (Continue): This is an interim response — no fix needed. The client should continue sending the request body. For 406 (Not Acceptable): Adjust the Accept header to a format the server supports.