Platform guards

System libraries only exist on their platform. Guard examples and tests before opening an OS-specific module.

if (process.platform !== 'darwin') {
  console.log('This example uses Security.framework and only runs on macOS.')
  process.exit(0)
}

For tests, use a skip guard:

const run = process.platform === 'linux' ? test : test.skip

Runtime requirements

• Bun and Deno ship native FFI.
• Node uses node:ffi where available, otherwise koffi.
• Deno scripts that load libraries need --allow-ffi; examples that read overrides also need --allow-env.
• None of these bindings run in the browser.

Library path overrides

Every shipped module accepts a direct override and an environment override:

await using libc = await openLibc('/lib/x86_64-linux-gnu/libc.so.6')

UNFFI_LIBC_PATH=/lib/x86_64-linux-gnu/libc.so.6 bun app.ts

macOS system libraries may live in the dyld shared cache. UnFFI accepts canonical framework paths such as /System/Library/Frameworks/CoreFoundation.framework/CoreFoundation even when they are not visible as ordinary files.