WebSocket
Mock 1010 Mandatory Extension Response
The client is terminating the connection because the server did not negotiate one or more expected extensions in the handshake response.
View full reference →1 HTTP Response
HTTP/1.1 1010 Mandatory Extension Content-Type: application/json Date: Tue, 25 Feb 2026 12:00:00 GMT
2 Test with curl
curl -i https://httpbin.org/status/1010
3 Return 1010 Mandatory Extension in Your Framework
django
from django.http import HttpResponse
def my_view(request):
return HttpResponse(status=1010) # Mandatory Extension
flask
from flask import Flask
app = Flask(__name__)
@app.route("/endpoint")
def my_endpoint():
return "", 1010 # Mandatory Extension
fastapi
from fastapi import FastAPI
from fastapi.responses import Response
app = FastAPI()
@app.get("/endpoint")
def my_endpoint():
return Response(status_code=1010) # Mandatory Extension
express.js
// Express.js
app.get('/endpoint', (req, res) => {
res.sendStatus(1010); // Mandatory Extension
});
spring boot
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
@RestController
public class MyController {
@GetMapping("/endpoint")
public ResponseEntity<Void> myEndpoint() {
return ResponseEntity
.status(1010) // Mandatory Extension
.build();
}
}
go net/http
package main
import "net/http"
func myHandler(w http.ResponseWriter, r *http.Request) {
w.WriteHeader(1010) // Mandatory Extension
}
ruby on rails
class MyController < ApplicationController
def my_action
head :mandatory_extension
end
end
asp.net core
// ASP.NET Core Minimal API
app.MapGet("/endpoint", () =>
Results.StatusCode(1010) // Mandatory Extension
);