Build settings
Build settings live under Settings → Build on a project. Leave a field empty to use the default described in Supported apps. Changes apply to the next deployment; they do not restart the running app.
Fields
| Field | What it does | Limit |
|---|---|---|
| Root directory | Folder inside the repository that contains the app's package.json. Relative to the repository root. | 300 characters |
| Install command | Replaces the package manager's default install. Runs inside the root directory. | 500 characters |
| Build command | Replaces the build script or framework default. | 500 characters |
| Start command | Replaces the framework default. Must start a server on port 3000 and keep running. | 500 characters |
| Node version | Recorded with each deployment for reference. Does not change the Node that runs, which is always 22. | 50 characters |
Whitespace-only values are treated as empty.
Root directory rules
- Leading and trailing slashes are removed;
.means the repository root. - Absolute paths and
..segments are rejected. - The folder must exist and contain a
package.json, otherwise the deployment fails at the build step with a message pointing back here.
Commands run in a shell
Each command is executed by sh -c inside the root directory, so you can chain steps:
npm run generate && npm run build
Environment variables you have set on the project are available to all three commands. The build has outbound internet access, so commands may fetch from registries or download tools.
Common overrides
Prisma or another code generator before build.
npx prisma generate && npm run build
A Node backend that compiles to a different entry point.
Start command:
node build/server.js
Skip a heavy install when the lockfile is stale. Set the install command to npm install to allow the lockfile to update. Prefer fixing the lockfile; frozen installs are the reason builds are reproducible.
Locked while deletion is scheduled
When a project is scheduled for deletion, build settings become read-only. Cancel the deletion from project settings to edit them again.
Audit trail
Every change to build settings is recorded in the project's Activity tab with who made it and when.