Extensions are the internal architecture of TYPO3. They are written in PHP. PHP 5.3 can be used with the full command set. TYPO3 also provides several library classes for better efficiency. Each extension is identified by a unique extension key.

TYPO3 Extension Development is based on the TYPO3. Being an open source technology it is freely available and downloaded without any license under general public license. TYPO3 CMS is built using PHP/MYSQL which is supported on all major browsers used in today's date. TYPO3 CMS is also available in enterprise version which is mostly used to deliver intricate and authoritative TYPO3 websites.

There are almost 4500+ pluggable TYPO3 extensions available. TYPO3 extension development can be used for small and mid-sized enterprises as it has powerful content management framework that offers unconventional operation with a total set of standard modules and healthy architecture that enables the higher performance of the all type of solution or extension. For TYPO3 developer the platform is quite intuitive and user friendly. The architecture of this CMS is such that it allows content editors to create and maintain web pages such a way as to make the whole process seamless and integrated with just few clicks.

Examples for popular extensions:
€ News (extension key: tt_news): Website news with front page teasers and article handling
€ TemplaVoila (extension key: tt_templavoila), a popular third-party template engineextension
€ RealURL (extension key: realurl): Creates SEO-friendly URLs, "pretty" URLs
€ Front End User Registration (extension key: sr_feuser_register): A self-registration system for website users
€ Direct Mail (extension key: direct_mail): Newsletter mailer system with options for personalized mails and feedback statistics

With TYPO3 extension development the web based communication and customer relations become much more interactive and meaningful. Web based communication that includes flawless integration of multimedia contents and project scope. When the business goes with TYPO3 CMS option, they have advantage of sharing internal messages and talks related to the development project. Apart from all browser compatibility TYPO3 also offer a special passage of creativity for designers.

In general, any developer with the reasonable PHP skills can program TYPO3 extensions. In fact one can also establish as a TYPO3 extension development company by hiring such professionals. The best part with TYPO3 CMS is that it allows you to write extension and customize code within its framework, thus allowing all business functions of any organization to be built into one framework. Business functions such as managing Forums, Event Calendars, News Listing, Document Management, E-Commerce functions, Template selection, Multilingual support, Multi country, Multi domain etc. are all built-in ready-to-use extensions within the TYPO3 framework.