Markdown is a lightweight markup language that uses plain text formatting syntax to produce formatted HTML. Created by John Gruber in 2004, it is the standard writing format for README files, GitHub wikis, documentation sites, and technical blogs. GitHub-Flavored Markdown (GFM) extends standard Markdown with tables, strikethrough, task lists, fenced code blocks with syntax highlighting, and auto-linked references.

InfraHub's Markdown Previewer renders GFM in real time with syntax highlighting, giving you an accurate preview of how your document will appear on GitHub or any Markdown-rendering platform.

Markdown is parsed using a GFM-compliant parser that converts the input into an abstract syntax tree (AST). Code blocks are syntax-highlighted using a tokenizer that recognizes keywords, strings, comments, and operators for dozens of programming languages. The rendered HTML is displayed in a live preview panel alongside the editor. The split-pane layout updates instantaneously as you type, with no round-trip to any server.

Developers write and preview GitHub README files before committing. Technical writers draft documentation articles and check formatting before publishing. Engineers write incident post-mortems or architecture decision records (ADRs) and preview them before sharing. Bloggers who publish on platforms like Dev.to or Hashnode preview their articles in Markdown before submission.