Redirects

Prevent Browser From Caching a 301 Redirect: Leverage Cache-Control Headers

June 18, 2024

5 minute read

There maybe times where you want to redirect a URL using HTTP 301 status code, which signifies a permanent redirect. However, what if you don't want this redirect to be cached by the browser? This is where the use of the Cache-Control header comes in handy.

This article will explain how to use the Cache-Control header to prevent browsers from caching 301 redirects. Additionally, we will discuss how to implement the various directives on popular web servers.

Why Prevent Browser Caching of 301 Redirects?

While the caching of 301 redirects is a good thing in most scenarios - it helps speed up navigation to commonly visited URLs - there may be circumstances where this is not the desired result. For instance, if you're in the process of developing a site and are frequently changing urls and redirects, caching can lead to confusion and erroneous results. Another use-case might be when your site has implemented temporary URL structures that may change over time, and you don't want your users to be stuck with the outdated structures.

Using the Cache-Control Header

The Cache-Control HTTP header is used to specify directives for caching mechanisms of http requests and responses. The directives specify who can cache the response, under which conditions, and for how long.

To prevent browsers from caching a 301 redirect, you can add the Cache-Control header with the no-store directive to your HTTP response. This tells the browser not to store a copy of the document in its cache.

Let's go through a basic example:


HTTP/1.1 301 Moved Permanently
Location: http://www.new-website.com
Cache-Control: no-store

In this example, the server sends back a 301 Moved Permanently status code, indicating that the requested resource has been assigned a new permanent URI and any future references to this resource should use one of the returned URIs. The Location field holds the new URI where the resource resides. The Cache-Control header with the no-store directive tells the client (the browser) not to cache this redirect.

Implementing the Cache-Control Header in Different Web Servers

The way you add the Cache-Control header will depend on your server software. Below are brief tutorials on how to do this in some popular web servers:

Apache

In Apache, you can use the .htaccess file to add headers to your HTTP responses. Lets look at how to implement this below:


<IfModule mod_headers.c>
    Header set Cache-Control "no-store"
</IfModule>

Nginx

In Nginx, you can add headers within a server or location block in your server configuration file. Lets look at how to implement this below:


location / {
    add_header Cache-Control "no-store";
}

Remember to reload or restart your server after making these changes for them to take effect.

Exploring Other Important Cache-Control Directives

The Cache-Control header has several other directives that allow you to control how, by whom, and for how long a resource can be cached. Let's look at a few more of these directives.

no-cache

Unlike no-store, the no-cache directive doesn't prevent the caching of a resource. Instead, it specifies that the stored response must be validated with the server every time before it's served. This ensures that users always receive the most up-to-date version of a resource, while still benefiting from caching.

In other words, no-cache allows a response to be cached, but tells the browser that it must not use the cached response without first checking with the server to see if there are any changes.

max-age

The max-age directive specifies the maximum amount of time (in seconds) a resource is considered fresh. Once this time has passed, the cached copy of the resource is considered stale, and the client will re-fetch the resource from the server.

For example, Cache-Control: max-age=3600 means that the resource can be cached, and that cache is valid for one hour.

public and private

public and private directives control where a resource can be cached.

If a response is marked public, it can be cached by any cache, including those that are shared among multiple users, such as a CDN. This is useful for resources that are the same for all users.

On the other hand, a response marked private is intended for a single user and must not be cached by a shared cache. A private browser cache (i.e., the cache on a user's local machine) can store such a response.

Combining Cache-Control Directives

These directives can be combined to achieve more specific caching policies. For example, Cache-Control: private, max-age=600 means that the response is specific to a single user and can be stored in the user's browser cache for up to 600 seconds.

It's important to remember that while using these directives provides you with greater control over how your responses are cached, not all browsers and caches respect all directives, and the exact behavior can sometimes depend on the specific browser and its version.

Final Thoughts:

Understanding the Cache-Control directives and their respective behaviors can greatly enhance your control over how your web resources are cached. While the no-store directive is particularly useful for preventing caching of 301 redirects, other directives like no-cache, max-age, and public/private provide also additional flexibility for managing web resource caching policies.

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