Build
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The process of compiling source code into a runnable application or deployable artifact.
A build is the process of transforming source code into something that can actually run, typically automated through CI/CD. For compiled languages, this means compiling code into machine instructions. For web applications, it means bundling JavaScript, compiling TypeScript, processing CSS, and generating static assets.
The build process catches errors that individual files cannot. A file might have valid syntax but reference a function that does not exist in another file. The build step connects all the pieces and fails if something does not fit.
Build times matter more than most teams realize. A 10-minute build that runs 50 times per day costs the team over 8 hours of waiting per day. Fast builds (under 2 minutes) keep developers in flow. Slow builds push developers to batch changes, skip CI, or context-switch while waiting.
Examples
A developer runs the build locally before pushing.
The developer runs npm run build. TypeScript compilation catches a type error: a function expects a string but receives a number. The developer fixes it before pushing. Without the build step, this error would have been caught by CI (slower feedback) or worse, in production.
A build fails in CI but passes locally.
The build passes on the developer's laptop but fails in CI. The cause: the developer has an environment variable set locally that CI does not have. The fix is to add the variable to the CI configuration. The 'works on my machine' problem is exactly what CI prevents.
A team optimizes their build time.
The build takes 8 minutes, mostly due to large dependency installations. The team adds build caching (dependencies only reinstall when package.json changes) and parallel compilation. Build time drops to 90 seconds. Developer productivity improves measurably.
In practice
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Frequently asked questions
What is the difference between a build and a deploy?
A build transforms source code into a runnable artifact (compiled binary, bundled JavaScript, Docker image). A deploy takes that artifact and puts it on servers where users can access it. Build creates the package. Deploy ships the package.
Why do builds fail?
Common causes: type errors (TypeScript finds a mismatch), missing dependencies (a package was not installed), import errors (a file references something that does not exist), and environment issues (a required variable or tool is not available in the build environment).
Related terms
Continuous integration and continuous deployment: automating code testing and delivery to production.
The process of releasing code to servers where users can access it.
Automated analysis of source code to flag programming errors, bugs, and style violations.
An automated test that verifies a small, isolated piece of code behaves correctly.
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