DNS Explained: What Happens Between Typing a URL and Loading a Page

Every developer uses DNS thousands of times a day without thinking about it. Then one day your deploy breaks because of a DNS propagation delay, or your site goes down because of a misconfigured CNAME, and suddenly you need to understand what is actually happening beneath example.com . I have been through this enough times to know that a basic understanding of DNS prevents hours of confused debugging. The lookup chain When you type example.com in your browser, a sequence of lookups happens before any HTTP request is made. 1. Browser cache. The browser checks if it has seen this domain recently. Chrome caches DNS results for 60 seconds by default. 2. OS cache. If the browser cache misses, the operating system's stub resolver checks its own cache. On macOS, this is handled by mDNSResponder . On Linux, it is systemd-resolved or the resolver library. 3. Recursive resolver. If the OS cache misses, the query goes to your configured DNS resolver -- typically your ISP's resolver or a public on