Promise.all() vs Promise.allSettled() in JavaScript

Promise.all() and Promise.allSettled() both run an array of promises concurrently, but they differ in how they handle failures. Promise.all() rejects immediately if any promise rejects; Promise.allSettled() always waits for every promise and reports each outcome individually.

Common causes

• Promise.all() is designed for "all-or-nothing" operations where a single failure means the whole batch is invalid
• Promise.allSettled() is designed for independent operations where you want to know the result of every promise regardless of individual failures

How to fix it

• Use Promise.all() when every result is required and any failure should short-circuit the rest, e.g. loading required config files
• Use Promise.allSettled() when partial success is acceptable, e.g. sending notifications to many users where one failing shouldn't stop the others
• Check each result's .status ('fulfilled' or 'rejected') when using allSettled() to branch on success/failure per item

Example

const results = await Promise.allSettled([fetch(a), fetch(b)])
results.forEach(r => {
  if (r.status === 'fulfilled') console.log(r.value)
  else console.error(r.reason)
})

FAQ

Does Promise.all() cancel the other promises when one rejects?

No — it rejects immediately with the first error, but the other promises keep running in the background; they're just no longer awaited by that Promise.all() call.