This wiki gives you information on how to create placeholders in your plugin that can be used in other plugins, how to use other placeholders inside your plugin, or how to make an expansion.
It also has a community-curated list of all available Placeholder expansions and their placeholders.
Pages aimed at server owners who want to utilize PlaceholderAPI.
Pages aimed at plugin developers who want to use PlaceholderAPI in their own plugin or want to make their own PlaceholderExpansion.
Common problems you may face while using PlaceholderAPI, and how to solve them.
Frequently Asked Questions and their answers.