solana-system-interface is used at run time in 133 crates (of which 13 optionally). It is a direct run-time dependency in 33 crates. It's used only as a dev dependency in 19 crates (of which 6 directly).

Depender (with downloads and own rev deps) solana-system-interface version
519K 80 spl-token-2022 ^1.0.0
360K 619 solana-program ^1.0
180K 2 spl-elgamal-registry ^1.0.0
166K 15 solana-config-program ^1.0
144K 135 solana-transaction-status ^1.0
139K 3 solana-thin-client ^1.0
130K 8 solana-stake-interface ^1.0
122K 2 solana-example-mocks ^1.0
94K 5 solana-client-traits ^1.0
90K 12 solana-system-transaction ^1.0
61K 20 solana-address-lookup-table-program ^1.0
142K 26 solana-perf optional ^1.0
134K 5 solana-vote-interface optional ^1.0
133K 45 solana-message optional ^1.0
126K 4 solana-feature-gate-interface optional ^1.0
124K 9 solana-loader-v3-interface optional ^1.0
124K 6 solana-loader-v4-interface optional ^1.0
39K 22 solana-bpf-loader-program ^1.0
38K 10 solana-system-program ^1.0
35K 11 solana-faucet ^1.0
100K 40 solana-transaction optional ^1.0
30K 5 solana-cost-model ^1.0
15K 27 solana-cli-output ^1.0
2.7K 4 litesvm ^1
1.8K 3 solana-cli ^1.0
330 1 spherenet-stake-interface ^1.0
270 litesvm-token ^1
120 spherenet-program ^1.0
230K 14 solana-cpi dev ^1.0
227K 15 solana-bincode dev ^1.0
139K 3 solana-rpc-client-nonce-utils dev ^1.0
104K 47 solana-clap-utils dev ^1.0
95K 29 solana-transaction-context dev ^1.0
23K 12 solana-svm-transaction dev ^1.0
21K 3 agave-transaction-view dev ^1.0
21K 12 solana-runtime-transaction dev ^1.0
16K 10 solana-clap-v3-utils dev ^1.0
13K 6 solana-compute-budget-instruction dev ^1.0
1.7K 6 mollusk-svm dev ^1.0