solana-system-interface is used at run time in 151 crates (of which 10 optionally). It is a direct run-time dependency in 27 crates. It's used only as a dev dependency in 37 crates (of which 6 directly).

Depender (with downloads and own rev deps) solana-system-interface version
285K 594 solana-program ^1.0
114K 15 solana-config-program ^1.0
107K 3 solana-thin-client ^1.0
103K 114 solana-transaction-status ^1.0
57K 6 solana-stake-interface ^1.0
53K 21 solana-address-lookup-table-program ^1.0
38K 21 solana-bpf-loader-program ^1.0
36K 9 solana-system-program ^1.0
106K 25 solana-perf optional ^1.0
33K 10 solana-faucet ^1.0
31K 5 solana-cost-model ^1.0
25K 1 solana-example-mocks ^1.0
21K 5 solana-client-traits ^1.0
20K 12 solana-system-transaction ^1.0
17K 27 solana-cli-output ^1.0
26K 35 solana-message optional ^1.0
26K 3 solana-feature-gate-interface optional ^1.0
25K 4 solana-loader-v3-interface optional ^1.0
25K 4 solana-loader-v4-interface optional ^1.0
26K 4 solana-vote-interface optional ^1.0
22K 32 solana-transaction optional ^1.0
1.5K 2 solana-cli ^1.0
107K 3 solana-rpc-client-nonce-utils dev ^1.0
95K 14 solana-bincode dev ^1.0
96K 9 solana-cpi dev ^1.0
81K 47 solana-clap-utils dev ^1.0
22K 17 solana-transaction-context dev ^1.0
17K 12 solana-runtime-transaction dev ^1.0
16K 3 agave-transaction-view dev ^1.0
16K 12 solana-svm-transaction dev ^1.0
14K 10 solana-clap-v3-utils dev ^1.0
650 5 mollusk-svm dev ^1.0
650 5 solana-compute-budget-instruction dev ^1.0