Pasting rich text preserves unwanted HTML structure

Phenomenon

When pasting content from external sources (like Word documents or web pages) into a contenteditable region in Safari, the HTML structure is preserved, including unwanted elements like <span> tags with inline styles, <div> elements, and other formatting markup.

Reproduction example

1. Copy formatted text from a Word document or web page.
2. Paste it into a contenteditable div in Safari.
3. Inspect the DOM structure of the pasted content.

Observed behavior

• Safari preserves the full HTML structure from the source.
• Unwanted elements like <span style="...">, <div>, and other formatting tags are included.
• The pasted content may have inconsistent styling.

Expected behavior

• The paste operation should normalize or clean the HTML structure.
• Or, there should be a way to control what gets pasted (plain text vs. formatted).