HTTP 100 Continue vs 415 Unsupported Media Type
HTTP 100 (Continue) is a 1xx Informational response, while 415 (Unsupported Media Type) 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, 415 means that the server refuses to accept the request because the Content-Type is not supported.
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 refuses to accept the request because the Content-Type is not supported.
When You See It
When sending JSON to an endpoint that only accepts XML, or missing the Content-Type header.
How to Fix
Set the correct Content-Type header matching the data format you're sending.
Key Differences
100 is a 1xx Informational response, while 415 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 415: The server refuses to accept the request because the Content-Type is not supported.
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 415 when when sending JSON to an endpoint that only accepts XML, or missing the Content-Type header.
When to Use Which
For 100 (Continue): This is an interim response — no fix needed. The client should continue sending the request body. For 415 (Unsupported Media Type): Set the correct Content-Type header matching the data format you're sending.