Software localisation and internationalisation are processes of adapting applications to a non-native background, namely other nations and cultures. Internationalisation involves the process of designing software in such a manner that it can be adapted to different languages and regions, while localisation is the process of adapting software for a specific language / culture by introducing locale-specific elements and translated text.

Some argue that development teams need to have human resources in place who couple a technical background with a deep knowledge of foreign languages and cultures. Others maintain that the commercial case to localise products into multiple languages and markets is very obvious, and all that is needed is a budgetary commitment from the software producers: it costs more to produce software for international markets, but English is only scarcely an option in an increasingly global economy.

Internationalisation and localisation are complementary, and must be combined to create an application that works at a global scale and screams out 'I'm user-friendly!'. Localisation-specific matters include:

• Local content
• Language translation
• Images and colours
• Aesthetics
• Symbols and icons
• Alphabets/scripts; different systems of numerals
• Spelling variants for different countries (e.g. European and Brazilian Portuguese)
• Date and time format, including different calendars
• Time zones
• Currency
• Units of measurement
• Printed materials and on-line support documentation
• Audio and subtitles, where applicable
  

The most common approach to software localisation is for applications to place text in resource strings which are then loaded during the execution of the programme. These strings, stored in resource files, are extremely easy to handle and can be exported to a multitude of different formats suitable for translation.

Consequently, to get a software application to support multiple languages, the application would be designed to select the relevant language resource file at runtime. Resource files are then translated to the required languages. The code required to manage country-sensitive data types must also support differing locale requirements. Modern development environments and operating systems include advanced libraries for international support of these types.