Question: What do you call the square brackets used to target a barcode/QR scanner? I thought this would be called "reticle," but when I Google the term, all I see are circles with crosshairs. Is there a more precise term, especially in the context of a digital device/camera, or is reticle the word?

![scanner target](https://i.stack.imgur.com/vYbtD.jpg)

Answer: 
I think the best term *is* "reticle." Businesses that make the glass used in cameras call them reticles. See the images on this site: <http://www.reticles.com/reticles_kr900.htm>.
Cross hairs are meant for aiming (centering) and are not usually interactive.

The rectangular visualization's primary purpose is not centering of focus, but selecting the relevant part of the image for scanning. Theoretically user can change both size and location in the screen, therefore this is not a common cross hair.

The rectangular visualization enables the user to see and modify the "region of interest". (See definition of "region of interest" or ROI here [[Wikipedia]](http://en.wikipedia.org/wiki/Region_of_interest), [[Mathworks]](http://www.mathworks.com/help/toolbox/images/f19-13234.html), [[Wolfram]](http://library.wolfram.com/examples/roi/)).

I found that this rectange is refered to as ["**viewfinder box**"](http://acer-tr.custhelp.com/app/answers/detail/a_id/16483/~/how-to-install-a-printer-with-acer-print), ["**viewfinder rectange**"](http://areacellphone.com/2010/05/howto-download-install-android-apps-using-qr-codes/), ["**viewfinder area**"](http://www.quickmark.cn/en/Info/android.asp), ["**crosshair box**"](http://www.cadtutor.net/forum/archive/index.php/t-17689.html) (or ["annoying yellow box around crosshair"](http://forums.steampowered.com/forums/showthread.php?t=1718837) in non-QR usage), however a more correct term (which is commonly used in image processing) would be "**region of interest**".

Relevent queries:

[viewfinder box](https://www.google.com/search?q=%22viewfinder+box%22+qr&hl=en&tbm=isch)  

[viewfinder rectangle](https://www.google.com/search?q=%22viewfinder+rectangle%22+qr&hl=en&tbm=isch)  

[viewfinder area](https://www.google.com/search?q=%22viewfinder+area%22+qr&hl=en&tbm=isch)