Web & Networking › How Browsers Work

What Happens When You Type a URL

DNS, TCP, TLS, HTTP, parsing, rendering: the classic end-to-end question.

Also known as: what happens when you type a URL in the browser, what happens when you visit a website, browser request lifecycle

A classic question because it ties the whole web together. Here is the journey from pressing Enter to seeing a page, in broad strokes.

1. Parse the URL. The browser splits https://example.com/products?id=7 into scheme, host, path and query (URL).

2. Check caches. It may already have the page, or part of it, in the browser cache, and then no request is needed.

3. Look up the IP address. DNS turns example.com into an IP, using caches along the way.

4. Open a connection. A TCP handshake establishes a reliable channel to that IP and port (443 for HTTPS). (HTTP/3 uses QUIC instead.)

5. Secure it. For HTTPS, a TLS handshake verifies the server’s certificate and sets up encryption (HTTPS).

6. Send the HTTP request. GET /products?id=7 with headers such as cookies and Accept (HTTP).

7. The server responds. Perhaps through a load balancer, app server and database. It returns a status code, headers and, usually, HTML.

8. The browser renders. It reads the HTML and builds the DOM; it fetches CSS, JavaScript, images and fonts, with further requests; builds the CSSOM; combines them into a render tree; works out sizes and positions (layout); and paints pixels (critical rendering path).

9. JavaScript runs, which may fetch more data and change the page.

Why it’s useful

When something is slow or broken, this list tells you where to look:

The network tab shows many of these stages with their timings.