Async I/O in Zig 0.16, today
Zig 0.16 introduced std.Io, a standard interface for I/O and concurrency, enabling libraries to work with different runtime implementations. While the built-in std.Io.Threaded uses OS threads and faces scalability limits, alternative implementations like zio offer efficient async I/O using system-level event mechanisms. Developers can now use zio to achieve high-concurrency performance without waiting for std.Io.Evented to mature.
- ▪Zig 0.16 includes std.Io, a cross-platform I/O and concurrency interface that supports pluggable implementations.
- ▪The default std.Io.Threaded implementation uses OS threads, which limits scalability due to system thread limits.
- ▪zio provides a full std.Io implementation using async I/O APIs like io_uring, kqueue, and IOCP, enabling efficient handling of tens of thousands of concurrent tasks.
- ▪Applications using zio can achieve true concurrency with minimal overhead, limited mainly by available memory.
- ▪Developers can use zio's io instance with standard Zig APIs such as std.http.Server for building scalable network services.
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Async I/O in Zig 0.16, today Lukáš Lalinský 2026-05-11 Categories programming Tags zignetworkingasync Zig 0.16 shipped last month with std.Io, a cross-platform interface for I/O and concurrency. This is a big step for the ecosystem. Libraries can now be written against a standard I/O abstraction, independent of the runtime, and application developers can plug in whatever implementation they want. The only usable implementation shipped with 0.16 is std.Io.Threaded, which uses a thread pool. When you spawn concurrent tasks, it creates OS threads to run them.
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