Q:

Is JSON a markup language like XML?

I'm a little bit confused, because some websites tell me JSON is not a markup language like XML, but a few say the opposite. Maybe you can give me some hint?

A:

From Wikipedia:

A (document) markup language is a modern system for annotating a
  document in a way that is syntactically distinguishable from the text.
  The idea and terminology evolved from the "marking up" of paper
  manuscripts, i.e., the revision instructions by editors, traditionally
  written with a blue pencil on authors' manuscripts.

So, no. JSON is not a Markup Language.
For that matter, nor is XML. Wikipedia describes it as "a meta markup language" since it provides a foundation for creating markup languages on.
JSON is like XML in that it is used to structure data in a text format and is commonly used to exchange data over the Internet.

A:

JSON is not a markup language. A dictionary definition of markup is:

a set of instructions on a manuscript or tags in an electronic document to determine styles of type, makeup of pages, and the like.

A markup language follows this theme. It is a syntax for annotating text with semantic meaning.

For example, when I put <i>italics on this text</i>, that is done with markup.

JSON doesn't/can't do that. JSON is simply a notation for encoding common computer data types in a readable form.

