What happens when you type google.com in your browser and press Enter

We take for granted how effortless it feels to open our browser, type a web address like google.com, and press “Enter” to instantly view the website. But in the seconds between hitting the key and seeing the page, dozens of complex technical processes rapidly unfold across servers around the world to make that instant gratification possible.

Let’s peel back the layers and dive deeper into the behind-the-scenes sequence that allows us to access google.com:

1. DNS Lookup to Find the IP Address

Your computing device must first find the actual server location of google.com before it can retrieve the website. To do this, it performs a DNS lookup. DNS stands for Domain Name System, which acts like an address book for websites.

When you type a domain name into your browser, your computer first checks its own DNS cache to see if it already has the website’s IP address stored and handy. The DNS cache stores recent query results locally so your computer doesn’t have to bug the DNS server every single time. If the IP address is not in the cache, your computer queries the configured DNS resolver, usually your Internet Service Provider’s DNS server.

For example, when you attempt to access google.com, your computer asks the DNS server “What is the current IP address for google.com?” The DNS server looks up the domain name in its registry and retrieves the corresponding IP address, which is currently 172.217.7.206. It returns the IP address back to your computer. Now your computer has the exact address it needs to find the Google web server.

2. Establish a TCP/IP Connection

Next, your browser establishes a direct connection to the Google web server using the TCP/IP protocol. TCP stands for Transmission Control Protocol while IP stands for Internet Protocol — these work together to define rules for how data should be transmitted over the internet.

Your computer “calls” the Google web server by sending a special TCP packet called a SYN. SYN stands for Synchronize, and it initiates the TCP handshake between the two devices. The Google server receives the SYN packet and responds with a SYN-ACK packet, confirming it got the call and is ready to connect.

Finally your computer returns an ACK packet, completing the TCP handshake and officially opening an active connection between your computer and the server. This TCP handshake process is like dialing a phone number and confirming someone answered before you start talking.

3. Get Past the Firewall

Large tech companies like Google have firewalls in place to filter out malicious traffic from attackers. Now that your computer has established a TCP connection directly with a Google server, that connection request still needs to get approved by their firewall.

The firewall inspects incoming connection requests before allowing them through. It verifies the IP address making the request, checks which port it’s directed to, and attempts to detect any suspicious activity. If it determines the request is safe and legitimate, the firewall grants access and allows your computer to communicate with the Google server.

Otherwise, if anything seems fishy about the connection, the firewall will block and discard the request to protect Google’s infrastructure. It’s like a security guard inspecting your ID and checking your bags before letting you enter an exclusive club.

4. Encrypted HTTPS Communication Begins

By default, Google uses HTTPS encryption to secure all communication between your device and its servers. The S in HTTPS stands for “Secure” specifically because it uses SSL (Secure Socket Layer) to encrypt traffic.

Once your computer is inside the firewall and access is granted, it can now share encryption keys directly with the Google server. The two devices encrypt all data they send back and forth using these keys so no third party can view or modify the traffic.

Even if hackers intercept the data, they can’t read any of the communication. It’s scrambled in what appears to be random gibberish to anyone except your computer and the intended Google server. Your communication is kept confidential and secure, just like whispering secrets back and forth so no one can eavesdrop.

5. Load Balancer Distributes Incoming Requests

A site as massively popular as Google get billions of requests from users across the globe every single day. A typical web server would crash under that kind of traffic overload.

To handle their enormous scale, Google deploys what’s known as a load balancer. This is a reverse proxy that sits in front of the Google web servers and distributes requests evenly across their server infrastructure.

The load balancer acts like a receptionist, taking incoming requests and forwarding them to available servers for processing. Based on advanced algorithms, it selects an optimal Google web server and routes your connection to that location.

This allows Google to efficiently spread the work across their network of servers. The load balancer also improves redundancy and failover since requests can be shifted from a downed server to a functioning one.

6. Web Server Retrieves HTML, CSS, JavaScript & Media

Now that the load balancer has passed your request along to an available Google web server, that particular server handles the work of gathering the necessary files to construct the google.com homepage.

The web server locates the main HTML, CSS, JavaScript, image files, fonts, and any other media needed to assemble the framework of the page. Think of the web server as a chef, collecting all the recipe ingredients from the pantry and refrigerator to start preparing a meal.

These base components of a webpage are relatively static and stored in cache to enable fast retrieval. The web server gathers them up and puts them on standby, ready to deliver part of the response.

7. Application Server Handles Dynamic Processing

While the core html and assets are static, some aspects of Google’s website involve dynamic processing and database lookups to build personalized content for each user. The web server delegates these requests to Google’s application servers.

Application servers handle critical backend processes like authenticating user credentials, analyzing search parameters, retrieving customized settings, rendering search results, and tapping into account preferences.

For example, Google’s application servers identify who you are based on your login cookies or device ID. It then pulls your unique user data to tailor the experience, like delivering search results in Spanish if that’s your preferred language.

Without the application server, each user would have an identical generic experience. It adds the logic and database queries to create a customized page.

8. Database Queries Retrieve Additional User Info

The application server frequently needs to query one or more databases to access specific user information like search history, geo-location, language preferences, ads settings, etc. Google maintains enormous distributed databases with profiles, analytics data, personalization metadata, and real-time usage stats.

When constructing your unique google.com experience, the application server queries just the bits of information it needs, like the fact that you always want to search from France rather than the U.S. It pulls these details from the database into memory as efficiently as possible.

Think of the application server as a prep cook fetching special ingredents for your personalized order. It grabs just what it needs from the vast storage pantry.

9. Web Server Returns Fully Rendered Page

Now the web server has all the foundational HTML, CSS, JavaScript, media files, coupled with the dynamically generated content from the application server. It compiles them together into a complete webpage response ready for your browser.

The web server runs any final processing, compression, and optimization tasks before sending the finished product back along the open TCP/IP connection to your computer. This all happens in milliseconds, and your browser receives and displays the freshly prepared google.com search page in seconds.

10. Browser Renders the Page for You

Finally, after the long journey of DNS lookups, server requests, firewall checks, proxies, caches, databases queries, and more…the simple result is your browser receiving and rendering the Google homepage you know and love!

Your browser displays the beautifully assembled HTML, CSS, JS, and media, allowing you to interact with the site and start searching. The complexity is all handled behind the scenes so that you can enjoy an optimized, personalized, and secure browsing experience.

11. Cookies Track Your Activity

Throughout your interaction with Google, various tracking cookies are created and stored in your browser for things like analytics, usage statistics, remembering preferences, and serving up related ads. Google deposits these tiny tracker files that allow it to identify you and your device specifically among the billions of other users.

Cookies are small text files that track browsing behavior, store sign-in credentials, and help provide a smooth personalized experience across Google products. They give Google insight about how you specifically utilize their services. Both first-party persistent cookies and third-party session cookies are leveraged.

Some are required just to operate basic site functionality, while others focus more on monitoring usage patterns and ad preferences. Google aims to balance cookies for customized features vs. privacy. As laws evolve, users are given more transparency and control over how their cookies are utilized.

12. Caching Speeds Up Repeat Visits

Now that you have accessed google.com once, your browser caches elements of the page locally so it doesn’t need to re-request everything on subsequent visits. Resources like logos, fonts, JavaScript files, and some content will be stored locally on your machine for faster repeat access.

Your browser may still need to re-check with Google’s servers for any dynamic updates, but caching static assets accelerates performance since they can be loaded directly from your device’s memory. Google’s servers benefit from having fewer redundant requests to process. It’s a win-win for delivering speedy page loads!

And that covers the life cycle of what happens behind the scenes when you visit google.com. From DNS queries to database lookups, many technologies work together seamlessly to deliver your requested page quickly, securely, and personalized to your preferences. Next time you press “Enter” in your browser, take a moment to appreciate the web’s complexity!