Is it safe to plug 20A device into 30A receptacle?

I'd think not, Guy. What sort of problem might you expect

If it's a crummy design, say high output resistance, a 30A load might be required to load its voltage down to the required value; but very unlikely

If you're at all concerned or if your load is especially sensitive to overvoltage, do acquire a voltmeter

With such high current such as your describing, it's a fairly odd question for someone to pose. Are you a technical person or a computer engineer or electrical engineer? What do your technical experts advise you on this? This is not something a layman should be messing with.

Rag I sort of disagree; Guy's q seems pretty reasonable and I don't see much chance for disaster

Am crossing fingers tho

My apologies to the OP. This is a total brain fart on my part as this is a different sort of router - not a computer router. Woodworking mechanical application.

This is me bowing out with tail tucked twixt my legs!

I hear ye Rag. But when a guy needs immediate help....

I had this problem, among others, of an annoying password requirement, where several a2k'ers suggested expert help--which would have set me back some $50-$150. But one a2k'er, a rare breed, having had such experience advised that Your Friendly Local Apple store might be of no help at all

Fortunately I have a very adept No. 1 Son who using phone contact resolved my difficulties

Incidentally for others who recently began using the new Apple OpSys, you'll notice how tabs, Contacts, and other such listings seem to disappear for no apparent reason. While there are ways to prevent this, some of them are very involved. One approach is never Shut Down. My No. 1 assures that Sleep instead, consumes only a few watts

Hard to get used to: For weeks you'll end your day still clicking Shut Down. Solution: Using felt pen, on surface of screen, cross out "Shut down"

scroll back. it was my misunderstanding.

S'okay Rag, I do it all the time

This was you being humorous, right?

No no, not at all Rag, perfectly serious. Perhaps you misunderstand, as somehow I often don't get across

Dale, if you write on your screen that'd be a poor choice, to say the least.
Why not write on a Post-it sticky note and tape it to the edge of the monitor somewhere? Why would you deface the screen and potentially block any text that appears there?

Returning the thread back to OP and running for the hills before Dale writes 'loser' on my forehead with felt-tip pen..

Oh but why

Already there are 15 other such

Hardly a big deal, Rag

Whaa, Rag, who, me

Incidentally I'd be first to admit there's a digital way to darken or delete "Shut Down" and I have not the slightest doubt my No. 1 would show me how; but I do overload his Inbox

Why not write these words backwards on your forehead with a diagonal line through it 'Don't Shut down'? Keep a mirror handy perched right over your monitor facing you so that you always see it!

Excellent idea, Rag, I shall dwell upon it

However my Better Half might object

Oh Guy forgive us. But have we been of any help at all

Getting back to the guy's question, 20 Amps is the maximum current the router needs. That means the outlet must supply at least that amount of current. A 30 Amp outlet is one that is rated to deliver up to 30 Amps. That means it is fine for the router. One the other hand if he plugged it into a 10 A or a 15 A outlet he would most likely trip a breaker/blow a fuse. Overvoltage is not an issue.

Okay Tes, I agree it probably isn't. But how can you be so sure

I generally think of this kind of thing as the Load pulling the current, rather than the source Pushing it. Tes is right.

with "Overvoltage is not an issue," I suppose. She's very competent in this area so I suppose she's right. But are you sure

Just pullin' ya leg Rog

Or am I pushin'

Both are true.