react.dev/docs/ref-07-special-non-dom-attributes.md

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special-non-dom-attributes	Special Non-DOM Attributes	docs	special-non-dom-attributes.html	dom-differences.html	reconciliation.html

Beside DOM differences, React offers some attributes that simply don't exist in DOM.

• key: an optional, unique identifier. When your component shuffles around during render passes, it might be destroyed and recreated due to the diff algorithm. Assigning it a key that persists makes sure the component stays. See more here.
• ref: see here.
• dangerouslySetInnerHTML: takes an object with the key __html and a DOM string as value. This is mainly for cooperating with DOM string manipulation libraries. Refer to the last example on the front page.