Developer tools: how to read requests/responses in Network and search for errors?

Effective work with developer tools in modern browsers starts with basic diagnostics of network activity and HTTP request analysis. The Network tab is the primary tool for frontend developers and testers, allowing you to track every request sent by the page. To successfully read requests and responses, as well as quickly find errors, you need to perform a series of preliminary preparation steps.

Before diving into deep network traffic analysis, it is recommended to reset your environment to its initial state. Update your browser to the latest version to avoid bugs from outdated software. Clear the cache and cookies for the problematic site, as old files can cause unpredictable application behavior. Disable third-party extensions one by one, since ad blockers or security scripts often interfere with network requests and distort the real picture of how the web resource works.

For more accurate problem diagnostics, always check the application's behavior in incognito private mode and in an alternative browser. This allows you to quickly figure out whether the root cause of the error lies in the site's own code or if it is caused by your current user profile, damaged local storage data, or conflicts with installed extensions. Once you have localized the problem and verified that it reproduces consistently, open the developer tools using the F12 or Ctrl+Shift+I keyboard shortcut and go to the Network tab.

Inside the Network tab, pay attention to the resource type filters: Fetch/XHR, JS, CSS, Img, and others. Reproduce the error by performing the required action on the page and examine the list of resulting request rows. Pay attention to status codes: 200 means success, 4xx indicate client errors, and 5xx signal server-side problems. By clicking on a specific request, you can examine its headers in detail, the payload in the Payload section, and the server response in the Response or Preview tab, which will help pinpoint the cause of the failure in the code or backend.