How does routing work in NestJS?

Question

Accepted Answer

**Routing** in NestJS is **decorator-based**: you map URL paths and HTTP methods to controller methods using decorators. The route prefix comes from `@Controller()` and the specific path + HTTP verb from method decorators like `@Get()` — combined to form the full route.

## How routes are composed

```ts
@Controller("users")          // PREFIX: all routes start with /users
export class UsersController {
  @Get()                       // GET /users
  findAll() {}

@Get("active")               // GET /users/active
  findActive() {}

@Get(":id")                  // GET /users/:id (dynamic parameter)
  findOne(@Param("id") id: string) {}

@Post()                      // POST /users
  create(@Body() dto: CreateUserDto) {}

@Put(":id")                  // PUT /users/:id
  update(@Param("id") id: string, @Body() dto: UpdateUserDto) {}

@Delete(":id")               // DELETE /users/:id
  remove(@Param("id") id: string) {}
}
```

The controller prefix + the method decorator's path combine: `@Get(":id")` inside `@Controller("users")` → `GET /users/:id`. Each HTTP verb has its own decorator (`@Get`, `@Post`, `@Put`, `@Patch`, `@Delete`).

## Route parameters and query strings

```ts
@Get(":id")
example(
  @Param("id") id: string,        // path param: /users/123 → id = "123"
  @Query("sort") sort: string,    // query: /users?sort=name → sort = "name"
  @Query() allQuery: any,         // the whole query object
) {}
```

## Nested/wildcard routes and sub-paths

```ts
@Controller("users")
export class UsersController {
  @Get(":id/posts")              // GET /users/:id/posts (nested resource)
  getUserPosts(@Param("id") id: string) {}

@Get("search/*")               // wildcard matching
  search() {}
}
```

## Route ordering matters

```ts
@Get("active")    // ✅ specific route FIRST
findActive() {}
@Get(":id")        // dynamic route AFTER — else "active" would match :id
findOne() {}
```

Specific (static) routes should be declared before dynamic (`:param`) ones, or the dynamic route may capture them.

## Global prefix and versioning

```ts
app.setGlobalPrefix("api/v1");   // all routes become /api/v1/...
// NestJS also supports API versioning (URI, header, media-type based)
```

A global prefix (e.g. `/api/v1`) applies to all routes — common for API conventions.

## Why it matters

Routing is fundamental — it defines your API's URL structure and is how every request reaches the right handler.

Understanding NestJS's **decorator-based routing** (the `@Controller` prefix combined with `@Get`/`@Post`/etc. method decorators to form full routes, and `@Param`/`@Query` to extract data) is essential everyday knowledge — it's how you build every endpoint, and the declarative style keeps routing clean and readable compared to manual route registration.

Knowing the practical details — composing prefixes and paths, handling route parameters and query strings, nested resource routes, the importance of **route ordering** (static before dynamic), and global prefixes/versioning for API conventions — is necessary for building well-structured REST APIs in NestJS.

Routing, controllers, and the parameter decorators together form the request-handling foundation of the framework, making this core, must-know material for any NestJS developer.