static.crates.io is the recommended upstream download
path. This avoids "403 Forbidden" rate limiting results
when trying to download crates too fast. This also
seems to improve download speeds/latency.
As per https://crates.io/data-access#crate-content,
Crates can be downloaded directly from the crates.io CDN
[...]
No rate limits apply to static.crates.io at present.
And as per https://crates.io/data-access#api,
you are welcome to use the crates.io API provided you abide by the following limits:
- A maximum of 1 request per second, and
- A user-agent header that identifies your application.