Possibly should. The only difference is the latency compared to Crucial RAM. Crucial is the most compatible with Dell systems and you can find that here.

Optiplex 780 Tech Guide  Then use "memory" for a search term.

Also see:  https://www.google.com/search?client=ms-android-americamovil-us-revc&ei=ZXX9XZncFYmStAaf-oDYCA&q=ddr3+vs.+ddr3l&oq=ddr3+vs.+&gs_l=mobile-gws-wiz-serp.1.0.0l2j0i22i30l6.162350.171967..174135...0.1..0.387.5191.0j15j5j5......0....1.......2..0i71j41j0i333j0i273j0i67j0i131j46i131j46.D3Mk4J5BEA8 

What different ram DDR3 or DDR3L? and all can use for 780 sff? Thank you.