||The verifiability of all or part of this article is disputed. (October 2009)|
A newsreader is an application program that reads articles on Usenet (a distributed discussion system, which groups its content into a hierarchy of subject-related newsgroups, each of which contains multiple threads or discussions). Newsreaders act as clients which connect to a news server, via the Network News Transfer Protocol (NNTP), to download articles and post new articles. In addition to text-based articles, Usenet is increasingly used to distribute binary files, generally in dedicated "binaries" newsgroups.
The term news reader is sometimes (erroneously) used interchangeably with news aggregator.
There are several different types of newsreaders, depending on the type of service the user needs — whether intended primarily for discussion or for downloading files posted to the alt.binaries hierarchy. Although Usenet originally started as a text-based messaging system without any file attachment ability, many Usenet users today do not participate in Network News Transfer Protocol discussion groups, as was common during the 1980s and 1990s before the emergence of website forums, and only use Newsgroups for downloading files such as music, movies, software and games. Therefore, their needs call for a streamlined client for quickly grabbing binary attachments, and without the extraneous clutter of text reading and posting features for which file downloaders have little use. As NZB files have largely replaced the inefficient and time-consuming process of having to download headers, many of the more recently-developed binary downloading clients have dropped header support entirely.
Types of clients 
The five general types are:
- Traditional newsreaders
- Designed primarily for reading/posting text posts; limited and often cumbersome binary attachment download functionality. Examples: most email clients such as Outlook and Netscape, as well as more specialized newsreaders such as Forté Agent, Xnews, nn, and tin.
- Binary grabbers/pluckers
- Used specifically for easy and efficient downloading of multi-part binary post attachments; limited or nonexistent reading/posting ability. These generally offer multi-server and multi-connection support. Most now support NZBs, and several either support or plan to support automatic Par2 processing. Examples: GrabIt, NewsBin, Newsleecher.
- NZB downloaders
- Are essentially binary grabber clients without header support; they can only load 3rd-party NZBs to download binary post attachments. Lacking support for viewing an NNTP server's grouplist or headers, they cannot browse groups or read/post text messages. Examples: NZB-O-Matic, SABnzbd, Ninan.
- Binary posting clients
- Designed specifically and exclusively for posting multi-part binary files. Example: PowerPost.
- Combination client
- A jack-of-all-trades that fully supports text reading/posting, as well as hassle-free multi-segment binary downloading and automatic Par2 processing. Being the most complex and feature-rich, these also tend to be the most difficult to learn. Example: Usenet Explorer.