Decoupling capacitor voltage

[Aztlanpz]

I am adding decoupling capacitor to a microcontroller  that are rate at 10 V is that an accountable margin  when the microcontroller  is running at 5 V?

[drussell]

I am adding decoupling capacitor to a microcontroller  that are rate at 10 V is that an accountable margent when the microcontroller  is running at 5 V?

Uhhh...

Yes, a decoupling capacitor rated for 10 volt maximum, continuous operation would have sufficient margin (voltage headroom?) for a microcontroller that is operating on a 5 volt supply in virtually every scenario.

Using a 6.3 volt on a 5 volt rail is about the absolute minimum limit but going to 10, 12, 16 volt in most design scenarios is a valid choice...  probably a wise one...

[mariush]

Decoupling capacitors are usually ceramic ones, in the 0.01 uF to 0.1uF ...  With ceramic capacitors it's sometimes important to be aware of voltage bias , see : https://www.maximintegrated.com/en/app-notes/index.mvp/id/5527 
Probably wouldn't matter for a microcontroller, but for other devices, maybe you'd want to use 25v or higher rated ceramic capacitors.

If you mean some bulk electrolytic capacitors like let's say 100-470uF or something like that, then yeah, 6.3v should be the minimum.  Note though that often 10v rated capacitors of such low values may have the same diameter and sometimes can be cheaper than 6.3v rated capacitors.
And for lower capacitances like 100uF or lower, voltage ratings like 25v and 35v are common, because you get around the same diameter and height regardless of voltage so makes no sense restricting yourself to 6.3v or 10v rating.