Observe fixed response delays

Prediction

A larger fixed server delay should increase browser elapsed time, but the two numbers should not be expected to match exactly.

Controlled observation

Choose 0, 250, 1000, or 3000 milliseconds. The response reports the selected fixture while the browser records elapsed time around the complete Fetch.

Explanation

Client-observed elapsed time includes more than application waiting. Connection, TLS, routing, queueing, edge execution, transfer, and browser scheduling can all contribute. This exercise isolates one known component without claiming to measure network latency or server processing independently.

HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
X-Lab-Scenario: delay

{"milliseconds":0,"scenario":"delay"}

'curl' '--include' '--request' 'GET' 'https://lab.httpclarity.com/v1/delay/0'

const response = await fetch("https://lab.httpclarity.com/v1/delay/0", {
  "method": "GET"
});
console.log(response.status, await response.text());

<?php
$options = ['http' => [
    'method' => 'GET',
    'ignore_errors' => true,
]];
$context = stream_context_create($options);
$body = file_get_contents('https://lab.httpclarity.com/v1/delay/0', false, $context);
var_dump($http_response_header, $body);