Download large data from iphones

To download more than 800 GB of data from an iPhone, you have a few options depending on your specific requirements and available resources. Here are some approaches you can consider:

1. If you have sufficient iCloud storage, you can back up your iPhone data to iCloud. Ensure that you have enough storage space in your iCloud account to accommodate the data you want to download. Once the backup is complete, you can access and download specific files or restore the entire backup to another device if needed. iCloud+ plans and pricing
2. Connect your iPhone to a computer with iTunes installed (or Finder on macOS Catalina and earlier). From there, you can back up your iPhone's data to your computer, including photos, videos, and other files. After the backup is complete, you can access and copy the desired files to your computer. Use iTunes to sync your iPhone, iPad, or iPod ... - Apple Support
3. If your data consists primarily of photos, videos, and documents, you can use cloud storage services such as Google Drive, Dropbox, or Microsoft OneDrive. Install the corresponding app on your iPhone, upload the data to your cloud storage account, and then access it from any device with an internet connection. Be aware that these services often have storage limits unless you purchase additional space.
   1. Use Files app and upload from iCloud Drive or (Any Cloud Drives (Google Drive, OneDrive, DropBox, Flickr, box, AmazonDrive, Adobe Creative Cloud etc) Watch the GIF below
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Consider the speed of your internet connection and the available storage space on your destination device when planning the transfer of such a large amount of data. Also, keep in mind that transferring such a large volume may take a significant amount of time and might require additional preparations, such as freeing up space on your iPhone if it's close to capacity.

You can use a 3rd party app like WeTransfer (Premium version), if you have a computer with a hard (or SSD disk) that can store more than 800GB .

What kind of dataa are these?

Download them to what?

Using Cable or Internet for downloading?

With the limited information that you have provided, It is hard to even guess the problems faced by you. 

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