I have been using Inkscape object>simplify a lot on my PC, but it does not work on a Mac. Is there anything that needs to be set to get this to work..? OS X Tiger.

Carel Struycken

Check in your preferences for the simplification threshold. I can't remember exactly where the setting is, but maybe it's set so low that it's not making any simplifications at all.

Yes! I found the setting under global preferences>miscellaneous. Strange that I had to set this to threshold 0.0060 on the Mac to get roughly the same effect as 0.0020 on a PC.

If they were different objects you might find that's why you needed different values. More complicated objects are better with much lower values, whilst more simple objects will work better with higher values.