How to resolve 'couldn't complete backup' error for WhatsApp on iPhone?

From Gemini

The "Deep Reset" for Persistent Glitches

If the backup has been stuck on "Preparing" or a specific percentage for days, a corrupted previous backup file in iCloud is likely blocking the new upload. You can safely clear this cache without deleting the actual messages on your phone:

1. Open your iPhone Settings and tap [Your Name] at the top.
2. Tap iCloud > Manage Account Storage (or Manage Storage).
3. Select WhatsApp Messenger from the list and tap Delete Data. (Note: This only deletes the broken cloud file, not your phone's history).
4. Go back one screen to iCloud, tap iCloud Drive, and turn it Off.
5. Launch WhatsApp, then close it completely.
6. Return to your iPhone Settings and turn iCloud Drive back On.
7. Reopen WhatsApp, go to Settings > Chats > Chat Backup, and tap Back Up Now.

Well, real working solution is:

• PROBABLY delete old backup on icloud (i wiped mine before testing)

• put phone into plane mode

• disable e2e key in wazzup

• kill the app cause it will start syncing

• open the app, go to backup section

• see no sync, disable plane mode

• create NEW e2e 64 digits key

• let it backup

i think whatsup devs are screwed something in the code so old keys wasn’t working anymore.

The "couldn't complete backup" error for WhatsApp on an iPhone is usually caused by a lack of available iCloud storage space or a temporary sync block with iCloud Drive.

You can resolve this issue and get your manual or automatic backups working again by following these troubleshooting steps:

• Check Your iCloud Storage: Go to Settings > [Your Name] > iCloud. If your available iCloud storage is less than the total size of your WhatsApp backup (plus some extra headroom), the upload will fail. You may need to clear out space or upgrade your storage plan.
• Delete an Existing Corrupted Backup: Open WhatsApp, go to Settings > Chats > Chat Backup, and tap Delete Backup. Clearing out an old, potentially stuck archive from iCloud allows WhatsApp to build a completely fresh backup file from scratch.
• Verify iCloud Drive Permissions: Go to Settings > [Your Name] > iCloud, tap Apps Using iCloud (or scroll down directly), and make sure iCloud Drive is turned on. Also, verify that the switch next to WhatsApp is toggled on so it has permission to save data to your cloud account.
• Switch Between Wi-Fi and Cellular: A fluctuating Wi-Fi network can cause the heavy upload process to time out. Try turning off Wi-Fi and running the backup using your cellular data connection, or switch to a different, highly stable Wi-Fi network.
• Sign Out and Back Into iCloud: If your Apple ID session is experiencing a minor authentication glitch, go to Settings > [Your Name], scroll to the bottom, and tap Sign Out. Restart your iPhone, then log back into your Apple ID to re-establish secure cloud sync permissions.

If the backup still refuses to complete, let me know:

• How many gigabytes of free space do you currently have left in your iCloud storage?
• Does WhatsApp give you an exact numerical error code or just a generic failure message?

I can provide a more advanced workaround if it's a persistent account-level error.

So had this same issue. I have two accounts on my WhatsApp, one of them backed up, the other didn’t. After deleting data from icloud and putting the sync back on, I turned off encryption (within the chat backup window) for the account that is not backing up and…magically, It started backing up

if deleting the app, re-starting the iPhone, and re-downloading the app does not clear this, ask WhatsApp Support.

Do NOT uninstall Whatsapp until this backup succeeds, else you lose everything!

Check if you have enough iCloud storage and update if necessary.

I tried everything and the thing that worked was disabling end-to-end encryption and it started backing up right away. After the backup has finalized, I enabled e2e encryption again.

For your third party app—

if in doubt search the developers website or contact their: Support/Help/FAQ/Known issues/compatibility/updates

Contact a third-party vendor - Apple Support

ref:

Contact WhatsApp

WhatsApp Help Center

How to contact WhatsApp Support

nikirage wrote:

Well, real working solution is:

Remove WhatsApp. Install Signal.

i think whatsup devs are screwed something in the code so old keys wasn’t working anymore.

valérie241 wrote:

I have plenty of storage, switched to data instead of WIFI, battery fully loaded, restarted the app. Is this happening to people with 2 accounts under one app? Nothing works so far.

Storage in iCloud ?

If you have 2 accounts you surely can't have them registered to the same app?? Which account is supposed to back up

gijs132 wrote:

I tried everything and the thing that worked was disabling end-to-end encryption and it started backing up right away. After the backup has finalized, I enabled e2e encryption again.

Well, that’s a bug. Arguably several.

I have plenty of storage, switched to data instead of WIFI, battery fully loaded, restarted the app. Is this happening to people with 2 accounts under one app? Nothing works so far.

I face same issue with backups.

i do not want to disable e2e key.

this issue exists since june/july 2026.

2nd account (almost empty) is backedup without issues encrypted OR not.