Drano can safely be used in toilets.
If the toilet is just slightly clogged then you can use Drano in your toilet and allow it to sit overnight or until the clog clears up.
Some slight clogs in toilets will clear using Drano but some other clogs in toilets may require plunging or augers for the toilet.
I have used Drano to clear a slightly clogged toilet before and it worked great.
However sometimes I've had a severely clogged toilet and it required plunging it and using a toilet auger and sometimes the problem was actually in the main sewer line.
In that case I hired a plumber to come out and clear my sewer line.
The best Drano product to use for toilets is Drano ® Max Build-Up Remover.