Redirect responses in NestJS - Step-by-Step Execution

Concept Flow - Redirect responses

Client sends request

↓

Controller method called

↓

Decide to redirect

↓

Send redirect response with status and URL

↓

Client receives redirect

↓

Client requests new URL

The server receives a request, decides to redirect, sends a redirect response, and the client follows the new URL.

Execution Sample

NestJS

import { Controller, Get, Res } from '@nestjs/common';
import { Response } from 'express';

@Controller()
export class AppController {
  @Get('old')
  redirect(@Res() res: Response) {
    return res.redirect(301, '/new');
  }
}

This code redirects requests from '/old' to '/new' with a 301 status.

Execution Table

Step	Action	Input/Condition	Response Sent	Client Behavior
1	Client sends GET request to '/old'	Request URL: /old	No response yet	Waiting
2	NestJS calls AppController.redirect	Route matches '/old'	No response yet	Waiting
3	Controller calls res.redirect(301, '/new')	Redirect status 301, URL '/new'	HTTP 301 with Location: /new	Receives redirect
4	Client receives 301 redirect	Status 301, Location '/new'	No new response yet	Sends GET request to '/new'
5	Client requests '/new'	Request URL: /new	Depends on '/new' handler	Follows new URL
6	Process ends for this redirect	Redirect complete	Final response from '/new'	Displays new page

💡 Redirect response sent with status 301 and Location header; client follows new URL

Variable Tracker

Variable	Start	After Step 3	After Step 4	Final
res	Express Response object	Redirect response prepared with status 301 and Location '/new'	Redirect response sent	Response cycle complete

Key Moments - 3 Insights

Why does the client send a new request after receiving the redirect?

Because the server sends a 301 status with a Location header (see execution_table step 3), the client knows to request the new URL.

What happens if we don't use @Res() and just return a string?

NestJS treats it as a normal response and does not redirect. Using @Res() lets us control the response directly (see execution_table step 3).

Can we change the redirect status code?

Yes, the first argument to res.redirect() is the status code (e.g., 301 or 302), controlling how the client handles the redirect (see execution_table step 3).

Visual Quiz - 3 Questions

Look at the execution_table, what response does the server send at step 3?

A HTTP 404 Not Found

B HTTP 200 with body 'Redirected'

C HTTP 301 with Location header '/new'

D No response sent yet

💡 Hint

Check the 'Response Sent' column at step 3 in execution_table

At which step does the client send the new request to '/new'?

A Step 5

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the 'Client Behavior' column for when the client requests '/new'

If we change the status code in res.redirect(301, '/new') to 302, what changes in the execution?

A The client does not redirect

B The client receives a 302 redirect instead of 301

C The server sends a 404 error

D The redirect URL changes automatically

💡 Hint

Refer to the 'Action' and 'Response Sent' columns in execution_table step 3

Concept Snapshot

NestJS redirect responses:
- Use @Res() to access Express Response
- Call res.redirect(statusCode, url) to send redirect
- Client receives status and Location header
- Client follows new URL automatically
- Common status codes: 301 (permanent), 302 (temporary)

Full Transcript

In NestJS, redirect responses happen when the server tells the client to go to a different URL. The client sends a request, the controller method runs, and if a redirect is needed, it uses the Express Response object's redirect method with a status code and new URL. The server sends back a response with that status and a Location header. The client then automatically requests the new URL. This process involves the controller method calling res.redirect(301, '/new'), sending a 301 status code and Location header. The client receives this and sends a new request to '/new'. This is how redirect responses work step-by-step in NestJS.