How to limit bandwidth rate in cURL

Controlling bandwidth usage prevents congestion and maintains fairness when multiple processes share a link. Rate limiting tests performance under throttled conditions and ensures compliance with bandwidth policies.

cURL can cap transfer speeds with --limit-rate, simulating slow connections or reducing server load. This provides stable, predictable performance and realistic testing scenarios.

Enforcing rate limits helps understand how applications behave under constrained bandwidth, offering insights into performance and user experience.

1. Open a terminal.
2. Use --limit-rate to cap download speed.

   $ curl --limit-rate 100k "https://www.example.com/largefile"

   100k sets a 100 KB/s limit. Adjust as needed.

3. Combine rate limiting with uploads.

   $ curl --limit-rate 50k --upload-file "/path/to/upload.txt" "ftp://ftp.example.com/" --user user:pass

   Rate limiting applies to both downloads and uploads.

4. Experiment with different rates for testing scenarios.

   Use m or g suffixes for MB/s or GB/s.

5. Check transfer times to confirm rate limiting effectiveness.

   $ curl --limit-rate 200k "https://www.example.com/mediumfile" --verbose

   --verbose output reveals the controlled transfer speed.