Troubleshooting Cookie Visibility Issues in Firefox Developer Tools for Modern Web Applications
In web development, inspecting cookies is a fundamental step for debugging authentication, session management, and other client-server interactions. Many developers rely on the browser’s developer tools to verify that cookies are properly set and transmitted. However, encountering situations where cookies are sent by the server and received by the client but do not appear under the Storage tab in Firefox can be perplexing. This article explores potential causes and solutions for this issue, with a focus on modern web development stacks such as React with Vite and FastAPI.
Understanding the Context
Developers working with single-page applications (SPAs) often utilize tools like React and Vite for a smooth development experience, combined with robust backend frameworks such as FastAPI. Cookies play a crucial role in managing authentication tokens, session data, and other client-server state.
Common Developer Workflow
Typically, when debugging authentication or state management, developers:
- Use browser developer tools, navigating to the Storage tab.
- Inspect the Cookies section to verify cookie presence, attributes (like expiry, Secure, HttpOnly), and correctness.
- Confirm that cookies are sent with requests by monitoring network traffic.
However, issues may arise where, despite the fact that network requests include cookies, these do not appear in the developer tools’ cookie storage view.
Potential Causes for Missing Cookies in Firefox Developer Tools
- HttpOnly Cookies
Cookies marked as HttpOnly are inaccessible to JavaScript and may sometimes be hidden or not listed in certain views. However, they should still appear in the Storage tab, unless filtered or misconfigured.
- Secure Cookies and Protocol Mismatch
If cookies are set with the Secure attribute, they will only be sent over HTTPS connections. While Firefox should still display these cookies, misconfiguration or working over an HTTP connection may affect their visibility.
- SameSite Attribute Settings
Modern browsers enforce strict SameSite policies. Cookies with SameSite=Strict or SameSite=Lax may restrict or alter their visibility in certain contexts, especially during cross-site requests. Similarly, some attributes influence how cookies are exposed in developer tools.
- Third-party Cookies and Subdomain Considerations
Cookies set as third-party or scoped to specific subdomains may not be visible in the main domain’s cookie storage. The way cookies are scoped affects their visibility.
- Vite’s Development Server and Proxy Configuration
During development, if proxy or server
