How can I determine if an address is on- or off-curve?

Question

It seems Solscan defaults to setting onCurve to false for addresses that don't have any transactions associated to it. How can I reliably check if a given address is on curve or not?

Answer 1

We can use the isOnCurve method of PublicKey from web3.js:

const onCurve = PublicKey.isOnCurve('ACYz3rCamFVGdub1BZ43yUnemp9PWNQBbn4KvPrrMeS1');

PS: It appears solana.fm doesn't have this bug, so can also just use that.