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I've got a question about the Chrome Developer Tools - Network Tab - "Content Download" part in the waterfall column. What exactly does this mean? Is latency somehow relevant to this?

Network "Content Download" Tab

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Hosted by SWU TeleNet GmbH (Ulm) [517.69 km]: 19.686 ms
Testing download speed................................................................................
Download: 1384.14 Mbit/s
Testing upload speed................................................................................................
Upload: 217.22 Mbit/s

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Hosted by DNS:NET Internet Service GmbH (Berlin) [2.30 km]: 17.918 ms
Testing download speed................................................................................
Download: 2455.88 Mbit/s
Testing upload speed................................................................................................
Upload: 684.83 Mbit/s
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  • Latency is super relevant for transfers over TCP. Check out TCP window scaling and the bandwidth-delay product.
    – Daniel B
    Commented Jul 16, 2023 at 8:22

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When you request something from a web server, you (generally1) send an HTTP request. How long it takes to send the request is measured in the "Request sent" field.

"Waiting (TTFB)" is the time between the end of the request and the start of the response form the web server. (TTFB stands for Time To First Byte.)

"Content Download" measures how long it took to download the response to the HTTP request after the latency is over.

There is more information available in the documentation.

I've seen two definitions for latency:

  1. The time between the request and the response. (This would be "Waiting (TTFB)")
  2. The amount of time it takes a packet to travel from the source to the destination. (This would affect "Content Download".)

1 I say "generally" because there are also other protocols in use on the web that aren't HTTP, but HTTP requests are what you're going to see most often in loading websites and activity from JavaScript requests.

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  • Thanks for your answers. You say: >The amount of time it takes a packet to travel from the source to the destination. (This would affect "Content Download".) I was wondering because I had to tests prepared with two VM instances. Both instances had an NGINX webserver configured serving one static picture. Depending on the distance to my VM, 2km or 520km, the test results differ by at least 150ms. Bandwidth doesn't seem to be the only factor here, since both VMs have enough bandwidth to transfer the 290k file within less then 1ms in theory.
    – mr.szop
    Commented Jul 22, 2019 at 9:50
  • @mr.szop Anything along the route from source to destination can affect your latency. It could be a delay on the server, a piece of the network infrastructure or on the host OS. If the server is located half way around the world, the packets will also take longer to travel.
    – Worthwelle
    Commented Jul 22, 2019 at 12:45

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