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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?

7/5/25, 7:07 pm1 repost3 likes

Stephen Cooper

@scooper.dev

8 May 2025

Ah looks like it has been raised as a Chrome issue but doesn't seem to have gone anywhere issues.chromium.org/issues/40488...

issues.chromium.orgChromium

Stephen Cooper

@scooper.dev

9 May 2025

What makes this even more interesting is that Chrome 136 looks to have improved things. But also the performance only really goes down when DevTools is open.

Stephen Cooper

@scooper.dev

8 May 2025

Ah maybe this is actually a Chrome related issue. Need to work out what is causing the following to take 50% of the performance profile. "Run Console Task" stackoverflow.com/questions/79...

stackoverflow.comWhat is "Run console task" in Chrome performance profilingI'm seeing some very slow performance in my JS code in an electron app I am trying to performance profile my application but the term that comes up is "Run console task" I have attached a

Stephen Cooper

@scooper.dev

7 May 2025

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.