A Usenet provider is a service that stores newsgroup posts uploaded to Usenet and then delivers them to anyone who requests them. Their retention amount is a crucial factor, as it determines how long posts are kept and available for access. The best Usenet providers offer high retention rates (upwards of 15 years), and build their  retention archive continually so no user posts ever expire. Larger Usenet archives provide the best search results and completion rates.
A Usenet indexer crawls the vast number of posts uploaded to Usenet and indexes them, making it easier for users to search for specific posts. While indexers can be helpful, they often come at an additional cost, and some may have restrictions on new member registration. Some of the top Usenet providers, such as Newshosting and Easynews, include a free  "newsreader" with Usenet search functionality, making a separate indexer a nice-to-have rather than a need-to-have.