typescript strict config

TypeScript Strict Mode Config

Understand when to enable strict mode and how to generate a strict tsconfig starter.

What strict mode buys you

Strict mode catches null handling, implicit any, unsafe class fields, and several categories of bugs before they reach runtime.

Migration advice

For existing projects, turn strict mode on in stages and fix the highest-value modules first. For new projects, start strict and avoid the cleanup cost later.

Strict starter

A strict starter should enable the umbrella `strict` flag and avoid weakening it with broad escape hatches. Add temporary suppressions only where migration work is tracked.

{
  "compilerOptions": {
    "strict": true,
    "noImplicitOverride": true,
    "noUncheckedIndexedAccess": true
  }
}

API boundary priority

Start migration at data boundaries: fetch responses, route params, form payloads, and environment config. These files usually produce the highest reliability gain from strict checks.

Team rollout

For large repositories, use a strict base config for new packages and a migration issue list for older packages. Avoid flipping every app at once without owners.

Before enabling in CI

Run the generated config locally, document remaining suppressions, and make the CI failure message point to the strict-mode migration guide.

Strict mode rollout map

Compiler area	What strict catches	Migration tactic
Null handling	Possibly null or undefined values.	Start with API and form boundaries.
Implicit any	Untyped parameters and weak callbacks.	Add types near public interfaces first.
Class fields	Uninitialized properties.	Prefer explicit constructors or optional fields.
Function types	Unsafe callback assumptions.	Tighten shared utility types gradually.

Use FrameworkKit to generate the starter code, then review the output before shipping it in production.

Generate with tsconfig Builder

tsconfig resources

tsconfig Builder

Generate TypeScript config presets for Next.js, Vite, Node, libraries, and strict mode projects.

tsconfig examples

Compare framework-aware TypeScript config starters before adapting your own project config.

tsconfig for Next.js

Start from a Next.js App Router TypeScript config and preserve generated route/framework types.

moduleResolution bundler vs node16

Choose TypeScript module resolution for bundlers, Node ESM, libraries, and monorepos.

tsconfig Builder vs manual config

Decide when a generated config starter is enough and when a project needs manual compiler options.

FAQ

Should new TypeScript projects use strict mode?

Yes. Strict mode is usually the right default for new TypeScript projects because it prevents avoidable runtime bugs early.

Is strict mode safe for old projects?

It can be safe, but enable it in stages. Start with high-value modules and avoid a single unowned migration PR.

Does strict mode replace runtime validation?

No. Strict mode checks source code, while runtime validation still protects API responses, form payloads, and external data.

Which strict option should I add first?

Use the umbrella `strict` flag for new projects. For legacy projects, start with null handling and implicit any cleanup where risk is highest.

Related comparisons

tsconfig Builder vs Manual Config

Compare generated tsconfig presets with hand-written TypeScript configuration.