Trace how a browser retrieves a web page
Follow the browser, DNS, IP address, web server and HTML from typed URL to displayed page.
Section 5 · The internet and its uses
This sequence follows Cambridge IGCSE Computer Science 0478, 2026–2028 syllabus Version 6. It covers subject content sections 5.1–5.3 only. The separately published 2029–2031 syllabus is not mapped here. Practice is original, self-checked and does not award an official Cambridge grade. Full timed papers and human subject-teacher review remain outstanding.
Before you begin
- No programming language is required. Be comfortable with place value and multiplication; each lesson introduces the computer-science notation it uses.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What does DNS look up?
What you will learn
- Explain the role of DNS
- Trace request and response between browser and server
- Explain how returned HTML becomes a displayed page
A URL starts a sequence of lookups and requests
When a user enters a URL, the browser reads the protocol and domain. The Domain Name System (DNS) looks up the domain and returns an IP address so network traffic can be routed to the server.
Apply and check the rule
The browser sends a request to that web server. The server returns a response that can contain HTML and other resources. The browser interprets and renders those resources to display the page. DNS finds the address; it does not deliver or render the page.
Pause and explain
When does the browser render HTML?
Worked example
Put these events in order: render HTML, resolve domain with DNS, enter URL, receive server response, request page.
Show the worked solution
- The user enters the URL.
- DNS resolves the domain to an IP address.
- The browser requests the page; the server responds; then the browser renders the HTML.
Answer Enter URL → DNS resolves the domain → browser requests the page → server responds → browser renders HTML.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Order the five steps after a student enters a domain: browser request, DNS lookup, server response, IP returned, page rendered.
Give me a hint
Name resolution must happen before routing the request.
Compare my reasoning
- DNS looks up the domain.
- It returns the IP address.
- The browser sends a request, the server responds, and the browser renders the page.
DNS lookup → IP returned → browser request → server response → page rendered.
Look for these in your work
- DNS first
- IP before request
- Response before rendering
The DNS lookup succeeds but the website server is offline. What will the browser receive?
Give me a hint
DNS and the web server perform separate jobs.
Compare my reasoning
- DNS can still provide the IP address.
- The browser then attempts to contact the server.
- If the server is offline, no successful page response is returned.
The name can resolve successfully, but the server cannot return the requested page while it is offline.
Look for these in your work
- DNS result separated
- Server contact
- Outcome explained
A learner says DNS converts HTML into the visible page. Correct the sequence and identify the component responsible for rendering.
Give me a hint
Compare name lookup with page display.
Compare my reasoning
- DNS resolves a domain name to an IP address.
- The web server returns page data such as HTML after a request.
- The browser renders that HTML for display.
DNS supplies an IP address; the server supplies page data; the browser renders the HTML.
Look for these in your work
- DNS role
- Server role
- Browser role
Common mistakes
- Saying DNS returns the page itself
- Saying the browser sends a domain name directly as the network destination without resolving it
What can you explain now?
What does DNS provide to help contact a website?
Compare with the explanation
The IP address associated with its domain name
The browser uses the IP address to route a request to the relevant server.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Name the roles of the browser, DNS, IP address, web server and HTML in a page request.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.