Why does call render and effects twice in development?

To reveal impure renders and effects without cleanup

To warm up the cache and speed up the first page load

It's a known React 18 bug; it's better to disable StrictMode

React · Junior · Question 34 of 75

Why does `<StrictMode>` call render and effects twice in development?

1To warm up the cache and speed up the first page load
✓Correct answer: To reveal impure renders and effects without cleanup
3It's a known React 18 bug; it's better to disable StrictMode

Explanation

The double call helps find side effects during render (mutations, requests) and missing cleanup in effects. It doesn't happen in the production build. If the double call breaks something, the code has a bug that will show up later anyway.

Why does `<StrictMode>` call render and effects twice in development?

Explanation

Further reading

Problem with a question

Test yourself

Why does <StrictMode> call render and effects twice in development?

Explanation

Further reading

Test yourself

Why does `<StrictMode>` call render and effects twice in development?