HTML source viewer

Paste markup, or open a .html file from this computer, and read it properly indented alongside a preview of the structure it describes. Everything happens in this tab.

Nothing loaded yet.

What this shows, and what it will not

The frame is sandboxed with scripting switched off, so markup is laid out and never executed. That is deliberate. It makes the tool safe to point at a file somebody sent you, and it means what you see is the document as written rather than whatever a script rebuilt it into.

It is a structure preview and not a faithful one. This site is served under a policy that lets it apply its own stylesheet and no other, and that policy covers the frame as well, so the document's own styling is not applied: not a stylesheet it links to, not a <style> block, not a style attribute. What comes back is the headings, lists, tables and links in document order, which is what you want when the question is how a page is built rather than how it looked.

Images and fonts hosted on other websites do not load either, for the same reason. Nothing you paste or open is sent anywhere: the tool could not upload it even if it tried, which is the same rule working in the other direction.

Doing this on a phone instead

This page is aimed at a computer. If the file is on an Android phone, the guide to opening an HTML file on Android covers what does and does not work there.