Is my script and style content changed?

No. Content inside script, style, pre and textarea is preserved verbatim.

Does it validate the HTML?

It formats best-effort for well-formed markup; it isn't a strict validator.

No. Formatting runs entirely on your device.

Format and indent HTML for readability, preserving script, style and pre content. Runs entirely in your browser — no uploads.

Pretty-print and indent messy HTML so the structure is clear. Great for cleaning up exported or minified markup.