Are scripts executed in the preview?

Scripts are blocked by default. The Allow scripts option changes the iframe sandbox so pasted scripts can run inside the preview.

Does the preview include my website’s CSS or assets?

Only the HTML you provide is written into the frame. External resources load only if the pasted markup references URLs that the browser can reach.

No. It shows how the browser renders the markup but does not perform standards validation or list conformance errors.

LocalFree

Paste HTML on the left, see it rendered live on the right inside a sandboxed iframe. Great for previewing emails, snippets, and components.

HTMLAllow scripts

Live preview

Runs in your browser; files and input stay on this device

1Paste HTML into the source pane.
2Watch the sandboxed preview update, and enable scripts only when you trust the code and need them.
3Edit the source until the rendered result matches your intent.

Are scripts executed in the preview?: Scripts are blocked by default. The Allow scripts option changes the iframe sandbox so pasted scripts can run inside the preview.
Does the preview include my website’s CSS or assets?: Only the HTML you provide is written into the frame. External resources load only if the pasted markup references URLs that the browser can reach.
Is this the same as validating HTML?: No. It shows how the browser renders the markup but does not perform standards validation or list conformance errors.