Delete large numbers of photos at once without deleting from Google+ backup

Question

I have about 5000 photos on my phone right now, and they are all backed up on Google+.

I know I can delete photos without removing them from Google+ by using the Photos app and selecting "On Device."

I also know that I can select multiple photos by selecting one, and then clicking more.

However, to quickly remove all photos, say, older than a month, I would need to individually click on 4000 thumbnails. Plus, when I do this for just 10 images it takes ~10 seconds to delete them. This would be a nightmare to do for 4000 photos.

Is there a way to batch-delete lots of photos from my phone, while ensuring that they won't get deleted from Google+?

(Alternatively, is there a way to delete-all locally, and selectively re-add photos from Google+?)

---

Edit (2017): This is obsolete ever since Google added the ability to "Free up space" from the menu in the Photos app.

Answer 1

You should be able to plug your phone into your computer and browse your files (probably under a folder called DCIM) using Windows Explorer (Not Internet Explorer but the file explorer) or Apple Finder. You might need to install the specific drivers for your phone if it doesn't automatically connect.

You can then sort your pictures based on date and remove everything past a certain date. They will not be deleted from Google+ since you are doing a local delete.

You can then download photos from Google+ that you want to keep locally.

Answer 2

The method I've found most convenient for mass deleting images locally is by using an FTP server app to allow access from my laptop. I use Ftp Server on my phone and FileZilla on my laptop, first backing up the images to my laptop, and then deleting them from my phone in the FileZilla interface. Since the images are generally named so they sort chronologically, it's dead simple in FileZilla to select the files older than a certain date and just hit delete once.