Do reviews loaded by JavaScript get indexed?

Google renders JavaScript and indexes what it produces, but on a delay and not guaranteed. Content in the initial HTML is indexed reliably; content that appears only after a script runs is indexed most of the time, later.

For a reviews widget that means the review text may or may not count as page content. The structured data it emits is a separate question with a better answer.

Googlebot crawls the HTML, queues the page for rendering, and comes back to run the JavaScript — sometimes within hours, sometimes considerably longer. What the script produces then gets indexed. Other crawlers, including several used by AI assistants, do less of this or none.

Assuming JavaScript content is invisible to search. It is not, and has not been for years. The real issue is the delay and the inconsistency, which matter for pages that change often and matter very little for a reviews block that is supplementary content.

The opposite mistake is assuming it is equivalent to server-rendered HTML. It is not, and for content you are relying on to rank a page, the difference is worth engineering around.

Reviews are supporting content. They help a visitor decide and add topical text to the page, but they are rarely what the page ranks for. The delay is therefore acceptable in a way it would not be for your main copy.

Structured data is the part that matters more, and it does not depend on rendering in the same way when emitted early.

Use URL Inspection in Search Console and look at the rendered HTML rather than the source. If the reviews appear there, Google saw them. Searching a distinctive phrase from a review in quotes is the crude version of the same test.