Is it free to use?

Yes it is. Really. You are allowed to do with the generated pictures what you want.

May I copy the source code and use it somewhere else?

Never ever. Copying of the source code is not allowed. As long as you just save/print the pictures you are save ;-)

How do I save/print the whole bunch?

Use right mouse click and then use "save picture as"
If you are using a mobile device try to tap longer on the picture until the popup containing print is visible.
The generated pictures are designed to be printed in standard A4 format, it should also match in the most other common formats.
To print the whole page press "CNTRL+P", it should work on most browsers.
The generator allows sizes from 9x9 up to 16x16. If the image doesn't fit on one page, try printing without borders.

Is it better to use a PC/Tablet?

Definitely. Generated Images are sligtly adopted to your screen resolution
Means, that on your smart phone you will get lower quality.

What about unique solutions?

There is no check!
Be sure, that that generated solution is most likely not the only one.
Some people say otherwise.
The intention of this site was that most generated/unproved Killersudokus got more than one solution.
If you want unique generated solutions just go there Killersudoku @ brain-stuff.de
The programm is now able to test generated Killersudokus for all solutions.

There is a big lag between pressing "generating" and showing one result

Yes, there it is! Please forgive us, we do not use all of your hardware our brains, so please be patient ...

"Show all" takes the whole night to compute all solutions?

Yes. Just when it is not expected. Even when fields are getting bigger.
Working on it.
If you press "Show all (use Threads)" it runs multithreaded and will use all of your CPUs.
It is scalable with the number of Your processors (or should). If not, write me a letter
It can still last all night.
Please note, if You are using a mobile device, it could drain Your battery rapidly.


Acknowledgments

Thanks to:
emscripten
Bootstrap
Without them this site would not exist.
Generator and Solver are written in C++ and transpiled via emscripten.