What are redirection status codes?

The detour sign of the web

Imagine you drive to your favorite restaurant, but there's a sign on the door: "We moved to 123 Main Street." You don't give up: you just follow the new address. That's what a 3xx redirection does on the web.

When a server responds with a 3xx status code, it's telling the client: "What you're looking for isn't here: but I'll tell you where to find it." The client (usually a browser) then automatically follows the new location.

How redirects work

A redirect response has two essential parts:

1. A 3xx status code: tells the client this is a redirect
2. A Location header: tells the client where to go next

HTTP/1.1 301 Moved Permanently
Location: https://www.example.com/new-page

The browser reads the Location header and automatically makes a new request to that URL. The user usually doesn't even notice: it happens in milliseconds.

The redirect flow

Here's what happens step by step:

Client                          Server
  |                               |
  |  GET /old-page HTTP/1.1       |
  |------------------------------>|
  |                               |
  |  301 Moved Permanently        |
  |  Location: /new-page          |
  |<------------------------------|
  |                               |
  |  GET /new-page HTTP/1.1       |
  |------------------------------>|
  |                               |
  |  200 OK                       |
  |  (actual content)             |
  |<------------------------------|

Notice: the client makes two requests. The first gets the redirect, the second gets the actual content. This is why excessive redirects slow down page loads.

The 3xx family at a glance

Not all redirects are the same. The 3xx range includes several codes, each with different behavior:

We'll cover each of these in detail throughout this course.

Why redirects matter

Redirects are everywhere in web development. Here are the most common use cases:

Moving content: When you restructure a website, old URLs need to point to new ones. Without redirects, users and search engines would hit dead ends.

Enforcing HTTPS: Most sites redirect http:// requests to https:// automatically. That's a redirect.

After form submissions: When a user submits a form (POST), you redirect them to a confirmation page (GET). This prevents duplicate submissions if they refresh the page.

Authentication flows: After signing in, users are redirected to their dashboard. After signing out, they're redirected to the home page.

Domain changes: When a company rebrands, old-domain.com redirects to new-domain.com.

Redirect chains and loops

Two problems can arise with redirects:

Redirect chains happen when one redirect leads to another, which leads to another:

/page-a → /page-b → /page-c → /page-d (final destination)

Each hop adds latency. Search engines may stop following after a few hops. Keep chains as short as possible: ideally just one redirect.

Redirect loops happen when redirects form a circle:

/page-a → /page-b → /page-a → /page-b → ...

Browsers detect this and show an error like "This page isn't working: too many redirects." This is a common bug in misconfigured applications.

Temporary vs. permanent

The most fundamental distinction in 3xx codes is whether a redirect is temporary or permanent:

Choosing the wrong type can cause real problems: a permanent redirect when you meant temporary can be very hard to undo, since browsers cache them aggressively.

Summary