Build once.
Reuse everywhere.

Once gives every action explicit inputs, outputs, and environment, so results are content-addressed, cached, and reusable across developers, coding agents, continuous integration, and machines. Build it once, and never build it again.

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$ once build apps/ios/App
target     apple_application
cache key  9f21c4…
result     hit
duration   0.8s

$ once build apps/android/App
target     android_binary
cache key  1c8ea7…
result     miss
duration   41s

$ once build crates/engine
target     rust_binary
cache key  b3f9d0…
result     hit
duration   0.1s

$ once build zig/app
target     zig_binary
cache key  77aa02…
result     hit
duration   0.3s

Build once

Give every action explicit inputs, outputs, and environment. Results are content-addressed, so a build only ever runs when something actually changed.

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Reuse everywhere

Restore outputs instantly from a local or shared cache across developers, coding agents, CI, and machines. Same inputs, same result, no rebuild.

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Run anywhere

Send only the declared inputs to a fresh local or hosted sandbox, run the action, and retrieve just the declared outputs.

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Works with your stack

Natively supported languages and ecosystems

Cache and reuse builds and tests across the tools your teams already ship with.

Swift Apple Kotlin Android Rust Go C / C++ Elixir Ruby JavaScript Zig React Native

Build once.Reuse everywhere.

Natively supported languages and ecosystems

Build once.
Reuse everywhere.