Some videos won't transfer from Photos to External Hard Drive

I'm running out of space on my computer and I don't want to delete anything before I solve this problem.

If you are saving these as a backup do you can delete the videos form Photos you should not be dragging and dropping them - you need the actual original which you can only get by exporting the unmodified original (in Photos File Menu ==> Export ==> export unmodified original

Same for both Photos and videos - drag and drop gives you an undefined preview usually of lower or much lower quality than the original

LN

I'm having troubles now as some videos won't transfer over to the hard drive when I drag them from Photos to my hard drive. It's only some videos, others transfer without a problem

When you drag videos from Photos, you are not saving the originals but the previews of the videos.

So Photos needs to render previews of the videos, and it may not be able to render the previews, if you are running out of storage or cannot process the video codecs. Try to use "File > Export > Export unmodified original" instead of drag and drop. Then you will save the videos in their original quality and not the previews in a reduced quality. Can you export the unmodified originals?

What kind of iPhone do you have and which version of iOS are you using? The iPhone may be using the new HEVC codec for the videos, that a Mac with Yosemite cannot process, see: Using HEIF or HEVC media on Apple devices - Apple Support

I tried exporting it didn't work

What happened. Did you get an error message? If yes, what has the message been?

If some photos or videos could be exported, what was the first video, that did not export? And what has the filename extension of that video been?

If you already haven't done so go to the Finder ➙ Preferences ➙ Advanced preferences and check this checkbox:

Then look at the end of the file name after the period: i.e. .jpeg, .mov, etc.

Yes

You either have to upgrade to High Sierra or you have to set your photo setting on your iPhone to use the automatic mode to transfer the most compatible format to Macs and PCs

LN