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I am in the process of evaluating the changes in React performance between v18 and v19. Prod fairly stable. Dev 19 is significantly slower. I know we should never measure performance in Dev but in reality a lot of developers are doing just that! Has anyone else noticed this?

Stephen Cooper

@scooper.dev

When profiling it looks to be related to the improved Error reporting that creates a JavaScript Error for each element. This really starts adding up if you have lots of elements on a page.

7/5/25, 7:40 pm0 reposts1 like

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