Q: Option to show sidebar in Photos on Mac is greyed out.

Have you tried the key combination option-command-S instead?

As a bow drawn at venture I'd try to delete the cached preferences files for the Photos.app and then restart the Mac.  This file can influence the graphical user interface.

I'd delete the complete folder ~/Library/Containers/com.apple.Photos/  and restart the Mac, then try again.

Your user library may still be hidden.To reveal the hidden User Library:

• Bring the Finder forward by clicking on the Desktop or the Finder icon in the Dock.
• Select your user/home folder (with the house icon in the Finder sidebar)
• With that Finder window as the front window, press the key combination ⌘J to bring up the View options.
• In the View options panel enable ’Show Library Folder’. That will make your user library folder visible in your Home folder.
• Open your Home folder, then the Library folder, then Containers.
• Move the complete folder ~/Library/Containers/com.apple.Photos to your desktop. Move the entire folder, not just the contents.

Now restart the Mac and try again.  If all is well, delete the folder from the Desktop.

Wow! Thanks. Scary, but it worked.

Great! You're welcome

Thank you!

Hello

I'm new to asking questions of a Community but I wondered if you could help me on this same problem of a greyed out Sidebar in Photos? I'm following the instructions you gave to 66sweep but I cannot find any Library in my Home Folder. I am not very adept at exactly what a Home or Library Folder is so any basic help in getting the sidebar in Photos to appear would be very welcome. Many thanks.

Have you tried to unhide the Library folder as I described?

Your user library may still be hidden.To reveal the hidden User Library:

• Bring the Finder forward by clicking on the Desktop or the Finder icon in the Dock.
• Select your user/home folder (with the house icon in the Finder sidebar)
• With that Finder window as the front window, press the key combination ⌘J to bring up the View options.
• In the View options panel enable ’Show Library Folder’. That will make your user library folder visible in your Home folder.
• Open your Home folder, then the Library folder, then Containers.
• Move the complete folder ~/Library/Containers/com.apple.Photos to your desktop. Move the entire folder, not just the contents.

Now restart the Mac and try again.  If all is well, delete the folder from the Desktop.

It should look like this:

Yes it worked! Very nice clear instructions - thank you so much.

You're welcome

I had imported photos from iPhoto to Photos and "show sidebar" was greyed out. I tried everything. An apple advisor figured out that the application window was too small. Once I dragged the corner to enlarge it, all kinds of wonderful things happened, including the sidebar option.

Once I dragged the corner to enlarge it, all kinds of wonderful things happened, including the sidebar option.

In Yosemite and El Capitan you can drag any side, not just the corners to enlarge a window. Very convenient if the corners are hidden.

Leonie . The pulling of the sides to enlarge is a very helpful tip. Thank you.

You're welcome

I fixed my Photos by simply making the window larger as PatStewart recommended.  But here is a weird thing. I tried your method and I can not find my house icon.  I have seen it and used it dozens of times before.  I can not find it now.

In the Finder/General preference pane be sure to select your Home folder in this menu:

Also in the Finder/Advanced preference pane be sure the Home folder is checked:

Now you should be able to quickly get to your Home folder from any Finder window.