The most important TypeScript best practice in 2026 is to enable strict mode and avoid any wherever possible. Lean on precise types, discriminated unions, unknown over any, and utility types to catch bugs at compile time instead of in production. Good types are documentation that never goes stale.
1. Always Use Strict Mode
Strict mode is non-negotiable for serious projects. It enables a family of checks that catch the majority of type bugs. Add noUncheckedIndexedAccess so array and object lookups are typed as possibly undefined, preventing common runtime crashes.
2. Avoid any, Prefer unknown
Using any disables type checking and defeats the purpose of TypeScript. When a value's type is truly unknown, use unknown and narrow it with type guards before use.
3. Model State with Discriminated Unions
Discriminated unions make impossible states impossible. Instead of optional booleans that can contradict each other, use a single status field with literal values like idle, loading, success, and error. The compiler then forces you to handle every case.
4. Use Utility and Derived Types
- Partial, Pick, Omit for shaping objects.
- ReturnType to type function outputs.
- as const to lock literal values.
- satisfies to validate without widening.
5. Validate External Data at Runtime
Types vanish at runtime, so API responses and form data need validation. In 2026, Zod remains the standard for schema validation that also infers TypeScript types automatically, keeping schemas and types in sync.
6. Keep Types Readable and Maintainable
| Do | Avoid |
|---|---|
| Name types clearly (UserProfile) | Cryptic names (T1, Data2) |
| Prefer type for unions | Overusing enum |
| Co-locate types with code | One giant types.ts file |
| Use readonly for immutability | Mutating shared objects |
7. Modern Tooling in 2026
- Use ESLint with typescript-eslint for consistent rules.
- Run tsc --noEmit in CI to block type errors.
- Adopt faster type-aware tools as they mature.
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Frequently Asked Questions
Should I use strict mode in TypeScript?
Yes, always enable strict mode for new projects. It activates checks like strictNullChecks and noImplicitAny that catch most type bugs before runtime. For existing codebases, migrate gradually by enabling strict flags one at a time.
What should I use instead of any in TypeScript?
Use unknown when a value's type is genuinely uncertain, then narrow it with type guards before use. For function generics, use type parameters. Reserve any only for rare migration scenarios and flag it with an ESLint rule.
Is Zod still the best validation library in 2026?
Zod remains the most popular choice in 2026 because it validates data at runtime and infers TypeScript types automatically. Alternatives like Valibot exist for smaller bundles, but Zod's ecosystem makes it the safe default.
When should I use type vs interface?
Use type for unions, intersections, and mapped types, and use interface for object shapes you may extend or merge, especially in libraries. In practice both work for objects, so pick one convention per project.
How do discriminated unions help in TypeScript?
Discriminated unions use a common literal field, like status, to let the compiler narrow types automatically in each branch. They make impossible states unrepresentable and force exhaustive handling, reducing bugs in state machines and API responses.