howfastly 2026.814.1

measure your connection speed to the fastly network
docs.rs failed to build howfastly-2026.814.1
Please check the build logs for more information.
See Builds for ideas on how to fix a failed build, or Metadata for how to configure docs.rs builds.
If you believe this is docs.rs' fault, open an issue.

HowFastly

Binary Cache:

HowFastly measures your connection speed to the Fastly network, running on Fastly Compute. Unlike fastly-debug.com, which only reports connectivity diagnostics, HowFastly measures throughput and latency, inspired by speed.cloudflare.com.

To install with cargo:

RUSTFLAGS='--cfg reqwest_unstable' cargo install howfastly

Or run without installing:

nix run \
  --substituters 'https://cache.ysun.co' \
  --trusted-public-keys 'cache.ysun.co-1:WxPYwT5g3kt9XhUhHPpNLZKI9HIOsVVAuqSHpok8Qt4=' \
  github:stepbrobd/howfastly#howfastly

See stepbrobd/inc#howfastly for packaging.

Nix users: multiple public binary cache instances like cache.nixos.org and cache.ysun.co are fronted by Fastly, so speedtest results are a fairly accurate representation of how fast binary cache fetches will run on your connection.

Methodology:

  • 25 unloaded latency pings (median, jitter, min, avg)
  • Download transfers from 100 kB to 100 MB, uploads from 100 kB to 50 MB
  • Per size iteration counts (8/8/6/4/2, larger transfers have lower relative variance so fewer repeats)
  • 30s time budget per direction (roughly 640 MB transferred worst case)
  • Reports p90 speed with loaded latency per direction (bufferbloat)
  • Server processing time calculated from samples using Server-Timing header
  • No packet loss measurement (this would requires raw UDP probes, which speed.cloudflare.com sends through a WebRTC TURN server native to the Cloudflare network, Fastly Compute cannot emit raw L3 frames, and Fastly does not have freely usable TURN server)

Sponsorship disclaimer

Not an official Fastly product or project. This project is generously supported by Fastly through the Fast Forward program. The views and content of this project are solely those of the author and do not imply endorsement by Fastly.

License

Apache-2.0