TYPO3 Multi-Domain Setup: Mastering a Base Installation for Multiple Websites

Introduction  

You are facing a challenge familiar to many companies: managing multiple digital presences centrally – from the main website and product pages to event microsites. The good news is that with TYPO3, this is not only possible but also extremely efficient.

A multi-domain setup with TYPO3 means: one installation, unlimited possibilities. You save on hosting costs, reduce maintenance efforts, and retain full control over your digital infrastructure.

In this guide, we will follow an HTTP request on its journey through the system – from the browser input to the final content delivery. You will understand not just how the configuration works, but more importantly, why.

Table of Contents  

Part 1: The Anatomy of a URL – What Your Browser Actually Sends  

Before configuring servers, we need to understand the language of the web. Every web request begins with a URL – let's look at what actually happens in the address bar.

URL Components in Detail  

Let's take a complex URL apart:

https://user:pass@myserver.at/folder1/folder2/datei.html#absatz3

The Request Journey at a Glance  

Before diving into the details, here is the overall process at a glance:

Let's examine each phase in detail.

Part 2: DNS – The Global Address Book of the Internet  

DNS (Domain Name System) is the foundation of all web communication. Browsers only understand IP addresses – DNS translates human-readable domain names into machine-readable IPs.

A-Record vs CNAME Record: The Crucial Choice  

There are two DNS record types for multi-domain setups. The choice has massive implications for performance and functionality:

DNS Configuration: Practical Implementation  

For our multi-domain setup with firma-a.de and projekt-b.com, you will need the following DNS records:

; Primary domains
firma-a.de.           IN  A    123.45.67.89
www.firma-a.de.       IN  A    123.45.67.89
projekt-b.com.        IN  A    123.45.67.89
www.projekt-b.com.    IN  A    123.45.67.89

; Email records work in parallel
firma-a.de.           IN  MX   10 mail.firma-a.de.
projekt-b.com.        IN  MX   10 mail.projekt-b.com.

Understanding DNS Propagation  

DNS changes are not immediately visible worldwide. Here is what happens:

Testing Propagation

Use tools such as DNS Checker, Google Admin Toolbox Dig or the CLI tool dig to verify global DNS propagation:

Web-based tools:

The Google Admin Toolbox Dig enables DNS lookups directly in the browser – ideal for quick checks without terminal access.

---

CLI-Tool:

Bash

dig firma-a.de +short
# Output: 123.45.67.89

Part 3: Apache Virtual Host – The Intelligent Traffic Director  

DNS has provided the IP address – now Apache receives the HTTP request. Its task is to route requests for hundreds of potential domains to the correct directories.

Virtual Hosts: One Server, Many Websites  

Imagine Apache as the reception hall of an office building. The IP address is the street address. The Host header in every HTTP request is like the company name on an envelope. Apache checks its configuration and routes the request to the correct 'office' (DocumentRoot).

Name-Based Virtual Hosts: The Configuration  

Name-based Virtual Hosts allow multiple websites on a single IP address – distinguished only by the domain name in the HTTP header.

<VirtualHost *:80>
  # DocumentRoot: The central entry point for all domains
  # All requests land here, regardless of the requested domain
  DocumentRoot /var/www/typo3

  # ServerName: The primary domain of this Virtual Host
  # Apache uses this if no other domain matches
  ServerName www.firma-a.de

  # ServerAlias: All other domains that also land here
  # Space-separated list of all additional domains
  ServerAlias firma-a.de www.projekt-b.com projekt-b.com

  # Logging for debugging and monitoring
  ErrorLog ${APACHE_LOG_DIR}/typo3_error.log

Multi-Domain with Separate DocumentRoots  

Sometimes you may want different TYPO3 installations per domain. Here is the advanced configuration:

# Virtual Host 1: Company A
<VirtualHost *:443>
  DocumentRoot /var/www/firma-a
  ServerName www.firma-a.de
  ServerAlias firma-a.de
  
  <Directory /var/www/firma-a>
      Options FollowSymLinks
      AllowOverride All
      Require all granted
  </Directory>
</VirtualHost>

# Virtual Host 2: Project B
<VirtualHost *:443>

Part 4: TYPO3 Site Management – The Content Engine  

Apache has forwarded the request – now TYPO3 takes over. The CMS must decide: which website should TYPO3 deliver for this domain?

The Foundation: The TYPO3 Page Tree  

TYPO3 manages all content in a hierarchical page tree. For every independent website, you need a root page.

Site Management Module: Modern Configuration  

Since TYPO3 v9, the Site Management module has replaced complex TypoScript configurations. It defines Entry Points – the link between a domain and a root page.

The config.yaml in Detail  

TYPO3 stores every site configuration as a YAML file. Here is the structure for our Company A:

# typo3conf/sites/firma_a/config.yaml
rootPageId: 1
base: 'https://www.firma-a.de/'

# Language configuration
languages:
-
  title: Deutsch
  enabled: true
  languageId: 0
  base: /
  typo3Language: de
  locale: de_DE.UTF-8
  iso-639-1: de
  navigationTitle: Deutsch

TYPO3 Request Matching: The Algorithm  

This is how TYPO3 decides which site is responsible for a request:

Important: TYPO3 checks both base AND baseVariants. The first matching configuration wins. In the event of multiple matches, the alphabetically first config.yaml takes precedence.

Part 5: The Complete Request Journey – End-to-End  

Let's track a complete request for www.projekt-b.com through all layers:

Request Details: The HTTP Headers  

What does the browser actually send? Let's take a look at the actual HTTP headers:

GET / HTTP/1.1
Host: www.projekt-b.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: de-DE,de;q=0.9,en;q=0.8
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
Upgrade-Insecure-Requests: 1

Troubleshooting: Common Errors  

Conclusion: Your Digital Infrastructure – Scalable and Future-Proof  

You have mastered the complete architecture of a TYPO3 multi-domain setup. From the DNS layer and Apache Virtual Host to the TYPO3 site configuration – you now understand how the individual components seamlessly integrate.

What You Have Achieved  

The Three Layers at a Glance  

Your Next Steps  

Best Practices for Production Operation  

Support & Further Resources  

Official Documentation:

• TYPO3 Site Handling Documentation
• Apache Virtual Host Documentation
• Let's Encrypt Certbot Guide

Tools:

• DNS Checker – Check global DNS propagation
• SSL Labs – Test SSL configuration
• GTmetrix – Performance analysis