This extension is for Google Chrome browser version 40.0.2214 and more.

1.Download the extension to a separate folder on your computer.

2. Go to the "Extensions" section of Google Chrome. 
   Click on Customize and control Google Chrome (three dots or a dash in the upper right corner
   of the browser bar - 1) -> More Tools (2) -> Extensions (3).

3. Check the checkbox for "Developer Mode" (1) -> 
   click on "Load Unpacked" (2) and in the opened window select
   the previously downloaded folder. Push the button to load (3)

4. The icon of our extension (1) appeared on the browser panel,
   on the right, and on the extension panel, 
   an extension appeared with the checkbox (2) turned on.

 Now the extension is fully operational and does not require 
 any additional settings.
 If necessary, you can disable it by moving this box.


Download media content

1.Google Plus Photo:
To download a photo from G +, open the photo in a new tab
 (right mouse button -> open photo in a new tab). 
Go to the new tab and press Shift + A.

2 Google Plus Video:
Start the video by clicking the play button.
Press a combination of buttons Shift + A,
and make a couple of clicks by right-clicking directly on the video.

3. Facebook video:
Open the video in a new tab and press Shift + A.
After full page reloading, click again Shift + A.
Now you have a video to download in the format .mp4

4. Twitter Photo:
Click on the photo of the post so that the photo opens in the frame 
and press Shift + A.
The photo will open in a convenient format for downloading in a new tab.
So you can download one or more photos. 
(if the photos are arranged in a group).

5. Twitter Video:
Open the video in a new tab or 
Click on the empty place of the post so that the video opens in the frame 
and press Shift + A.
Start the video and click again Shift + A.
Now you have a video to download in the format .mp4

6. Instagram:
To download photos and videos, there is one sequence of actions.
Click on the selected object and open it in the frame.
click Shift + A.
In a new tab, photos and videos will be opened 
in a convenient format for download.

If you did not seem to have enough of this information, then you can read my post and see the explanations in the pictures.
SMD - social media downloader.
https://abcinblog.blogspot.com/2018/04/smd-social-media-downloader.html

All rights reserved.
Created with love Yaroslav Kolesnikov.