# How builds work

A build turns source code into a container image that Koo can deploy. Builds run for two source kinds: deploys [from Git](/docs/deploy/deploy-from-git) and archives uploaded with [koo up](/docs/deploy/koo-up). [Container deploys](/docs/deploy/deploy-a-container) bring their own image and skip the builder — nothing else on this page applies to them.

## Where builds sit in the pipeline

A [deployment](/docs/deploy/deployments-and-rollback) that starts from source moves `queued` → `building` → `built` → `applied`. A deploy that ships an existing image — a container deploy, or a rollback — skips the two build statuses and goes from `queued` straight to being applied.

A failed build fails the deployment before anything reaches your service: the running version keeps running, and the build error is recorded on the deployment.

## How the image gets made

If your project has a `Dockerfile` at its root, Koo builds with it — the same image a local `docker build` would produce. Without one, Koo detects your language and framework and prepares the build itself; when detection isn't enough, it generates a Dockerfile with AI and builds from that. Either way the result is a normal container image, rolled out like any other deploy.

A Git deploy that resolves to a commit Koo has already built reuses that image instead of building it again.

## Build logs

Build output lands on the deployment: open the service's **Deployments** tab and select the version to read its build log, streaming live while the build runs and kept afterwards. The [Deployments API](/api/deployments) exposes the same log on the deployment's build-logs endpoint. Image deploys have no build, so they carry no build log.

## When builds won't start

A deploy is refused — with the reason in the error — while your account is still being provisioned, and while it is suspended. There is no per-hour cap on builds: plan limits apply to what you run, not how often you ship — see [usage and limits](/docs/account/usage-and-limits) for your plan's ceilings.