-
Notifications
You must be signed in to change notification settings - Fork 22.4k
/
index.md
79 lines (55 loc) · 2.99 KB
/
index.md
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
---
title: "PerformanceResourceTiming: secureConnectionStart property"
short-title: secureConnectionStart
slug: Web/API/PerformanceResourceTiming/secureConnectionStart
page-type: web-api-instance-property
browser-compat: api.PerformanceResourceTiming.secureConnectionStart
---
{{APIRef("Performance API")}}
The **`secureConnectionStart`** read-only property returns a {{domxref("DOMHighResTimeStamp","timestamp")}} immediately before the browser starts the handshake process to secure the current connection. If a secure connection is not used, the property returns zero.
## Value
The `secureConnectionStart` property can have the following values:
- A {{domxref("DOMHighResTimeStamp")}} indicating the time immediately before the browser starts the handshake process to secure the current connection if the resource is fetched over a secure connection.
- `0` if no secure connection is used.
- `0` if the resource was instantaneously retrieved from a cache.
- `0` if the resource is a cross-origin request and no {{HTTPHeader("Timing-Allow-Origin")}} HTTP response header is used.
## Examples
### Measuring TLS negotiation time
The `secureConnectionStart` and {{domxref("PerformanceResourceTiming.requestStart", "requestStart")}} properties can be used to measure how long it takes for the TLS negotiation to happen.
```js
const tls = entry.requestStart - entry.secureConnectionStart;
```
Example using a {{domxref("PerformanceObserver")}}, which notifies of new `resource` performance entries as they are recorded in the browser's performance timeline. Use the `buffered` option to access entries from before the observer creation.
```js
const observer = new PerformanceObserver((list) => {
list.getEntries().forEach((entry) => {
const tls = entry.requestStart - entry.secureConnectionStart;
if (tls > 0) {
console.log(`${entry.name}: TLS negotiation duration: ${tls}ms`);
}
});
});
observer.observe({ type: "resource", buffered: true });
```
Example using {{domxref("Performance.getEntriesByType()")}}, which only shows `resource` performance entries present in the browser's performance timeline at the time you call this method:
```js
const resources = performance.getEntriesByType("resource");
resources.forEach((entry) => {
const tls = entry.requestStart - entry.secureConnectionStart;
if (tls > 0) {
console.log(`${entry.name}: TLS negotiation duration: ${tls}ms`);
}
});
```
### Cross-origin timing information
If the value of the `secureConnectionStart` property is `0`, the resource is either not using a secure connection or it is a cross-origin request. To allow seeing cross-origin timing information, the {{HTTPHeader("Timing-Allow-Origin")}} HTTP response header needs to be set.
For example, to allow `https://developer.mozilla.org` to see timing resources, the cross-origin resource should send:
```http
Timing-Allow-Origin: https://developer.mozilla.org
```
## Specifications
{{Specifications}}
## Browser compatibility
{{Compat}}
## See also
- {{HTTPHeader("Timing-Allow-Origin")}}