Are custom DOM attributes supported in React v16?

Note: This question references React v16, which is outdated. The information below applies to React 16+, including current versions (React 18/19).

Yes. Starting with React 16, React no longer ignores unknown DOM attributes. If you write JSX with an attribute that React doesn't recognize, React will pass it through to the DOM.

For example, let's take a look at the below attribute:

<div mycustomattribute={"something"} />

In React 15 and earlier, this would render an empty div:

<div />

In React 16 and later (including React 18/19), any unknown attributes will end up in the DOM:

<div mycustomattribute="something" />

This is useful for supplying browser-specific non-standard attributes, trying new DOM APIs, and integrating with opinionated third-party libraries.