View source for Filename extension

{{FormatInfo
|formattype=electronic
|subcat=Elements of File Formats
}}
A '''filename extension''' (or '''file extension''') is a suffix of a [[filename]], usually the part after the last "<code>.</code>" (period). It is a crude but convenient way to help indicate the format or type of the file.

The details of how, and whether, filename extensions are used differ by [[Operating Systems|operating system]], but in the internet age they have developed some degree of universality.

Some operating systems limited extensions to three letters, and many three-letter strings are still in common use as extensions, but the current-day popular systems don't have this limitation and there are many longer extensions in use.

== See also ==
* [[Electronic File Formats]]
* [[:Category:File formats by extension]]

== Links ==
* [[Wikipedia: Filename extension]]

[[Category:Naming and numbering systems]]
[[Category:Metadata]]