Built-in APIs Highlights Summary

Every highlight bullet from the 9 pages in this section, gathered on one page and grouped by the page it came from.

The Node.js Standard Library

• Built-in modules are compiled into the Node binary itself - no install, no node_modules resolution
• Each built-in API carries a documented Stability Index level that governs how freely it can change
• Node has two builtin families: Node-native APIs (fs, http) and adopted Web Platform APIs (fetch, URL)
• TypeScript needs @types/node because builtins are C++-bound, not self-describing

Built-in APIs Basics

• Built-in modules load without npm install
• node: prefix avoids package name collisions
• fs, http, crypto, path cover most service needs
• Prefer promises APIs over callback variants

path and url

• path module handles OS filesystem paths
• url module parses HTTP URLs and file URLs
• import.meta.url resolves ESM module locations
• Use path.posix for S3 keys and URL pathname segments

Timers and Scheduler

• timers/promises integrates with async/await and AbortSignal
• setInterval can overlap if callbacks run long
• scheduler.postTask is limited in Node server contexts
• Use cron/queues for wall-clock schedules in production

fs and fs/promises

• fs/promises is default for async file I/O
• createReadStream for large files
• Avoid readFileSync on request paths
• watch with caution - noisy on macOS

util and diagnostics

• promisify converts callback-last APIs to Promises
• inspect controls depth for safe logging
• debuglog gates verbose logs behind NODE_DEBUG
• styleText and parseEnv aid CLI tooling

crypto

• randomBytes and randomUUID for tokens and IDs
• createHmac for webhook signature verification
• timingSafeEqual compares secrets without timing leaks
• Prefer Web Crypto subtle for some AES-GCM flows

os and process

• os module describes the machine Node runs on
• process.env reads environment configuration
• availableParallelism sizes worker pools
• memoryUsage and cpuUsage aid production debugging

Built-in APIs Best Practices

• Prefer node:fs/promises and pipeline over sync fs
• Use crypto built-ins for tokens and HMAC
• Validate env with schema, not raw process.env spreads
• Add npm dependency only when built-in is insufficient