HTTP 100 — Continue
HTTP 100 is an interim response telling the client to keep going: the request headers have been received and look fine, and the server is now waiting for the body. It only appears when the client asked for it by sending an Expect: 100-continue header.
When 100 shows up
- Large uploads: a client sends headers first and waits for 100 before streaming megabytes of payload.
- Clients that probe before committing an expensive or long request body.
Mocking a 100 response
A response with this status can be faked end to end with a local mock rule — no backend changes needed. The configuration below mirrors the rule fields the ApiSimul editor uses (method, path, status, delay in milliseconds, response body):
{
"method": "GET",
"path": "/api/upload",
"status": 100,
"delay": 120,
"enabled": true,
"body": null
}Dynamic placeholders such as {{random.name}}, {{string.uuid}} or {{number.int 1 100}} can appear inside the body to vary each response, which keeps client-side list rendering and retry logic honest during development.
Frequently asked questions
What does HTTP 100 mean?
It means the initial part of the request was accepted and the client should send the rest. On its own it never carries a body and is never the final answer to a request.
How can I test a 100 response without a real backend?
Define a mock rule with the method and path your client requests and set the status to 100. The example configuration above returns this response after the listed delay, so the client exercises its 100 handling exactly as it would against a live server.
Related status codes
Need the response in your own project? Spin up rules for any status with the ApiSimul mock server, or browse every status code page.