- For the Unicode table, see Appendix:Unicode.
Wiktionary uses the UTF-8 encoding of Unicode, which allows many languages and writing systems to be used alongside each other. While there are many writing systems encoded in Unicode, operating systems by default do not ship with fonts that cover these writing systems. This page tries to cover some Unicode issues.
If you only need to look up English words (or any other Western European language), any computer will suffice. However, if you want to display other languages auch as Arabic or Chinese, or extinct languages such as cuneiform and Gothic, there are certain system requirements that need to be fulfilled to be able to view these scripts.
Wiktionary has been confirmed to work with most modern Linux distributions and Windows Vista Service Pack 1. Users of Windows Vista RTM, Windows XP and Windows 2000 will need to update certain system files to be able to view all scripts.
Firefox is, at this time, the only browser that fully supports Wiktionary. Internet Explorer and Opera fail at certain scripts, though the effect can be remedied to a certain extent by script templates that force certain fonts.
Enabling complex language support
Some languages, such as Arabic or Hindi, need complex language support for correct display. This is enabled by default on most Linux distributions and Windows Vista, but Windows XP and Windows 2000 need to explicitely enable complex language support. The option can be found in the Control Panel, in Regional Language options.
Also, Windows 2000 and Windows XP do not have supplementary planes enabled by default, so ancient scripts might fail to display even if the correct font is installed. If you're affected, please follow these instructions to enable surrogates.
Latin (also includes IPA and transliteration)
Western, Central and Eastern European languages using the Latin script will most certainly be supported by your system. However, if you have problems viewing African languages, Native American languages, transliteration or IPA, you should install the DejaVu fonts, which supports some (but not all) of extended Latin.
Greek itself should work fine, polytonic Greek, however, might not.
Windows Vista supports polytonic Greek by default. Windows XP installs a font called Palatino Linotype which also supports polytonic Greek, but is not used by default. Users of other operating systems should install the New Athena Unicode font, which, while it may not be aesthetically appealing, supports all Greek letters in Unicode. DejaVu Sans also supports polytonic Greek.
If the Arabic letters do not join properly, please refer to #Enabling complex language support.
That said, Arabic, Persian and Urdu will most likely work. If, however, languages like Pashto and Uyghur will not display properly (letters will not join or even fail to appear) you should download the Scheherazade font and install it on your computer.
Users of Windows 2000 and Windows XP can go to Regional Options and install East Asian support. This will install Korean fonts that will allow the user to view Hangul and Hanja. This is installed by default on Windows Vista.
Users of other operating systems may want to install the Un Fonts. They have an advantage over the Windows fonts in that they support Old Hangul and Unicode 5.2 Hangul, but are somewhat lacking in Hanja.
If you get squares when trying to view Mycenaean Greek definitions, you need to download the Aegean font and install it on your computer.
If entries in Ugaritic script show up as squares on your computer, you need to download the Aegean font and install it on your computer.
Old Persian Cuneiform
If your computer fails to display Old Persian Cuneiform, downloading the Aegean font will most likely resolve the issue.
For Akkadian, please download the Akkadian font  and install it on your computer.
Identifying a font
To find out what font your browser is using for some text in Chrome and Firefox, right-click on the text, press Inspect, and find the right part of the browser's developer tools. In Chrome, the fonts for the text that you right-clicked are listed at the bottom of the Computed tab (screenshot). In Firefox they are listed in the Fonts tab.