HTTP 100 Continue vs 422 Unprocessable Content
HTTP 100 (Continue) is a 1xx Informational response, while 422 (Unprocessable Content) 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, 422 means that the server understands the content type and syntax, but was unable to process the contained instructions. Common in API validation errors.
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 understands the content type and syntax, but was unable to process the contained instructions. Common in API validation errors.
When You See It
When form validation fails — correct syntax but invalid data (e.g., email format wrong, date in the past).
How to Fix
Check the response body for specific validation errors and correct the input data.
Key Differences
100 is a 1xx Informational response, while 422 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 422: The server understands the content type and syntax, but was unable to process the contained instructions. Common in API validation errors.
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 422 when when form validation fails — correct syntax but invalid data (e.g., email format wrong, date in the past).
When to Use Which
For 100 (Continue): This is an interim response — no fix needed. The client should continue sending the request body. For 422 (Unprocessable Content): Check the response body for specific validation errors and correct the input data.