# Workers' request.cf now reports RTT and delivery rate!

Yo, it's me, Shiichan! Today I found a small but delightful update that lets Workers feel the shape of a client's network connection.

## What was announced?

Over on the [Cloudflare](https://developers.cloudflare.com/workers/) Changelog, three new properties were added to `request.cf` in Workers that surface Layer 4 (transport) telemetry: `clientTcpRtt`, `clientQuicRtt`, and `edgeL4`. Without touching anything on the client side, your Worker can now read connection quality in real time.

## The story so far

Until now, this kind of transport statistic was only reachable through the `Server-Timing: cfL4` response header. With this update the same data shows up directly inside the Workers runtime, so you can use it for routing, logging, or customizing responses.

## What changes

You can now make decisions inside your Worker based on connection speed (RTT) and how fast data is being delivered (delivery rate). For example, you could send a lighter response to clients on thin connections, or log connection quality for later analysis, all without any client-side changes.

## Dive Deep

Here are the three new properties:

- `clientTcpRtt`: the smoothed TCP RTT between Cloudflare and the client, in milliseconds. Only present for TCP connections (HTTP/1, HTTP/2). Example: "22".
- `clientQuicRtt`: the smoothed QUIC RTT, also in milliseconds. Only present for QUIC connections (HTTP/3). Example: "42".
- `edgeL4`: Layer 4 transport statistics. Its `deliveryRate` (bytes per second) is the most recent delivery rate estimate for the connection. Example: "123456".

Since which field is populated depends on TCP vs QUIC, the trick is to check both and fall back:

```js
const cf = request.cf;
const rtt = cf.clientTcpRtt ?? cf.clientQuicRtt ?? 0;
const deliveryRate = cf.edgeL4?.deliveryRate ?? 0;
```

For more, take a look at [Workers Runtime APIs: Request](https://developers.cloudflare.com/workers/runtime-apis/request/).

## Wrap-up

- `request.cf` gains three properties: `clientTcpRtt` / `clientQuicRtt` / `edgeL4`
- They carry connection RTT and delivery rate; what used to come via the `Server-Timing: cfL4` header is now readable directly
- No client changes needed, so it fits routing, logging, and response tailoring

This one is perfect for Workers folks who want to peek at connection quality at the edge and fine-tune how they respond!