It is highly recommended to use the online translator, which can be found at WebTranslator2. It offers a highly integrated translation process which lets the user focus on the translation itself.

When usage of the online translator is not possible, you can do a manual translation. Here are some translation guidelines which you should follow closely in this case.

• Please contact the development team before begining the translation process! This avoids double work, as someone else may have already started translating to the same language.
• Translators must use the charater set ISO 8859-15, otherwise, some characters will not display correctly in the game.
• Stable support only available to translations into 'latin' languages; support for other languages (cyrillic, asian, or other character sets) is available through utf8 branch, and still considered experimental.

So, now that you've notified the development team about your intention to translate (You did, right? Of course you did.) you can pick up and translate the latest english.txt (found in the SVN repository under /lang) or the one now provided with your release since 0.3.1.

Copy english.txt to a new file and change the first four lines of the file appropriately:

##name English-Name-Of-Language
##ownname Native-Name-Of-Language
##isocode ISO-Code-Of-Language
##plural List-Of-Plural-Types

Note: Do not alter the following parts of the file:

• String identifiers (the first word on each line)
• Parts of the strings which are in curly braces (such as {STRING})
• Lines beginning with ## (such as ##id), other than the first four lines of the file

Since version 0.4.0.1 of the game, OpenTTD supports a vastly improved translation system. It can handle multiple cases for words (like 1 house, 2 houses, 5 housies, etc.), different text depending on the context, and so on. Have a look on the wiki for an (incomplete) list of these features.

Failure to comply may cause bad things to happen such as a swarm of midget ninjas jumping at you from behind and practicing graffiti on your face, for instance. This is also known to happen to people who do not notify the development team about their endeavour.

In order to play the game in the translated language, you need to compile your file with the 'strgen' utility, which is included in the installation.

'strgen' is a command-line utility. It takes the language filename as parameter.

Example:

strgen lang/german.txt

This results in compiling german.txt and produces another file named german.lng. Any missing strings are replaced with the english strings.
Note that 'strgen' looks for english.txt in the lang subdirectory, which is where your language file should also be. That's all! You should now be able to select the language in the game options.