TYPO3 Multi-Domain Setup: One Installation, Many Sites

Introduction  

You are facing a challenge familiar to many companies: managing several digital presences from one place — the main website, product pages, event microsites and more. The good news is that with TYPO3 this is not only possible but remarkably efficient.

A TYPO3 multi-domain setup means one installation, unlimited possibilities. You cut hosting costs, reduce maintenance and keep full control over your digital infrastructure.

In this guide, we follow an HTTP request on its journey through the system, from the moment you type a URL to the final content delivery. You will come away understanding 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 we configure any servers, we need to understand the language of the web. Every web request begins with a URL, so let's look at what actually happens in the address bar.

URL Components in Detail  

Let's pull a complex URL apart:

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

The Request Journey at a Glance  

Before we dive 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, so DNS translates human-readable domain names into machine-readable IPs.

A-Record vs CNAME Record: The Crucial Choice  

Multi-domain setups rely on two DNS record types, and the choice between them has a major impact on performance and functionality:

DNS Configuration: Practical Implementation  

For our multi-domain setup with firma-a.de and projekt-b.com, you 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 visible worldwide straight away. Here is what happens:

Testing Propagation

Use tools such as DNS Checker, Google Admin Toolbox Dig or the dig command-line tool to check global DNS propagation:

Web-based tools:

The Google Admin Toolbox Dig runs DNS lookups directly in the browser, which is ideal for a quick check when you have no terminal to hand.

---

CLI-Tool:

Bash

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

Part 3: Apache Virtual Host – The Intelligent Traffic Director  

DNS has handed over the IP address, and now Apache receives the HTTP request. Its job is to route requests for hundreds of potential domains to the right directories.

Virtual Hosts: One Server, Many Websites  

Think of Apache as the reception desk of an office building. The IP address is the street address, and the Host header in every HTTP request is like the company name on the envelope. Apache checks its configuration and sends the request to the right 'office' (DocumentRoot).

Name-Based Virtual Hosts: The Configuration  

Name-based virtual hosts let you run 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 want a separate TYPO3 installation per domain. Here is the more 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, and now TYPO3 takes over. The CMS has one decision to make: which website should it serve for this domain?

The Foundation: The TYPO3 Page Tree  

TYPO3 keeps all content in a hierarchical page tree. Every independent website needs its own root page.

Site Management Module: Modern Configuration  

Since TYPO3 v9, the Site Management module has replaced the old, complex TypoScript configuration. 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 site:

# config/sites/firma_a/config.yaml (Composer installation)
# Legacy path: 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
  navigationTitle: Deutsch

TYPO3 Request Matching: The Algorithm  

Here is how TYPO3 decides which site is responsible for a given request:

Important: TYPO3 checks both base and baseVariants, and the first matching configuration wins. If more than one matches, the alphabetically first config.yaml takes precedence.

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

Let's trace a complete request for www.projekt-b.com through every layer:

Request Details: The HTTP Headers  

What does the browser actually send? Let's look at the real 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 now seen the full architecture of a TYPO3 multi-domain setup. From the DNS layer and Apache virtual host through to the TYPO3 site configuration, you understand how the individual pieces fit together.

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 your SSL configuration
• GTmetrix — performance analysis