How HTML Beautifiers Work
Published: January 15, 2026
Author: HTML Beautifier Team
Reading Time: ~1 min read
Published on: | By Web Dev Team
Have you ever wondered how an HTML beautifier knows exactly where to put a line break? It is more complex than simple regular expressions.
Tokenization
First, the beautifier reads the raw text and breaks it into tokens. It identifies opening tags, closing tags, text nodes, and comments.
Parsing and the AST
Next, it builds an Abstract Syntax Tree (AST). It understands that an <li> is a child of a <ul>, and tracks the current nesting depth.
Re-rendering
Finally, it walks through the AST and re-constructs the text string. For every level of depth, it adds a specific amount of whitespace (like 2 spaces). It also applies rules, like keeping inline tags (e.g., <span>) on the same line as surrounding text.