How to view 2 photos side by side for comparison?

It is in Beta at the moment, I think it will be released soon, but Photos Workbench will let you compare images side by side.

https://www.houdah.com/photosWorkbench/

It is a companion to Photos that addresses some of its deficiencies (I think the developers are watching this discussion!) like geocoding, keywords and comparing.

Warning: This is Beta Software! I have had no issues, but keep lots of backups.

Not Photos, Photos Workbench, from Houdah Software

Not possible in photos or preview.

In photos you can step quickly back and forth between two photos using the left/right arrow key which is a good way of comparing.

There are obviously apps that can do this - but I'm not aware of any that aren't also full featured photo editors - so not normally something you'd use alongside the photos app.

Where is it hiding in the current Beta of Photos, Keith? I have not yet discovered this useful tool. It is not mentioned in the Ventura Preview. The only comparison tool I can find is the new "Duplicate" album, where I can see duplicates side-by-side, but I have not found any way to compare arbitrary photos enlarged side-by-side.

That looks like a useful addition...

I misunderstood, sorry. Thank you for the clarification.

I should point out that I will only mention the Photos Workbench Beta if someone asks about something - like a compare - that is simply impossible with Photos.