Signed URLs vs Signed Cookies for Secure File Access in Web Apps

Overview

Access to private files, like user documents, videos, or downloadable reports, is essential in modern web apps. Whether you’re working on a video streaming platform, a document management system, or a SaaS dashboard, you want to ensure that users can only access what they’re authorized to see.

In this post, we will explain what each one does, when you should use them, and how to integrate them into a React application.

Signed URL

A Signed URL is a special link generated by your backend that allows access to a specific file for a limited time. Think of it like a VIP pass, it’s valid for a short duration, after which it stops working.

Common Use Cases

• Allowing a user to download a PDF report or invoice.
• Previewing protected images or videos.
• Letting third parties (clients, vendors, etc.) temporarily access content without logging in.

How It Works?

1. Your backend generates a unique URL with a cryptographic signature and expiration time.
2. The frontend uses this URL to access the resource directly from the cloud storage or CDN.
3. Once the time expires, the link becomes invalid.

These URLs are great for short-term, single-resource access. However, because the entire authorization is embedded in the URL, sharing the link can be risky if not tightly time bound.

Signed Cookie

A Signed Cookie is another way to authorize access, but instead of putting the access token in the URL, it’s stored in the user’s browser as a cookie. This approach is ideal when users need to access multiple files or stream content over time.

Common Use Cases

• Video/audio streaming where files are split into segments.
• Logged-in users accessing multiple protected images or documents.
• Any session-based content that requires consistent access.

How It Works?

1. After the user is authenticated, the backend sends cookies containing the access policy and signature.
2. These cookies are stored in the browser.
3. The cookies are automatically included for every request made to the CDN or cloud storage, allowing access as long as they are valid.

Signed cookies are more seamless for end users, especially when navigating multiple files.

Comparing Signed URLs and Signed Cookies

A signed URL is quick and easy if you deliver a single file. But if users browse or stream a set of files, like videos or images, signed cookies provide a smoother experience.

How This Fits into React

When building React applications, you must load protected content on the client side. Here’s how both methods play out in a real-world setup:

Using Signed URLs in React

With signed URLs, the implementation is simple.

You get the signed URL from your backend and plug it into the src of an image, video, or anchor tag. Be cautious not to expose these URLs too long or cache them in public places.

Using Signed Cookies in React

With signed cookies, the frontend doesn’t handle the cookies directly. Your backend sets the cookies using HTTP headers. Once set, the browser automatically includes them with every request to the content domain.

React doesn’t have to do much here – as long as your server sets cookies properly, your app will have access to all the content that uses those cookies for authentication.

Backend Setup (example):

• Set cookie headers with Secure, HttpOnly, and SameSite
• Match cookie domain with CDN or storage bucket domain.
• For server-rendered apps like Next.js, set cookies in getServerSideProps.

This method is cleaner for user experience, especially when your app needs to load multiple protected files in one session.

When Should You Use Each?

Conclusion

Signed URLs and Signed Cookies are great tools for controlling access to private content in your web applications. Your choice depends on the content type, access pattern, and user experience you want to deliver.

• Use Signed URLs for simple, one-off access.
• Use Signed Cookies for more complex, session-based, or streaming content.

From a React perspective, signed URLs are easier to work with, but signed cookies create a smoother user experience – especially when working with CDNs or cloud-based file systems.

Drop a query if you have any questions regarding Signed URLs or Signed Cookies and we will get back to you quickly.

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