[Ethereum] Is Ethereum wallet address case sensitive


I sent some amount of ETH to a wallet. I checked the wallets balance on ether chain. I entered the address in the search field and noticed both lowercase and uppercase versions of the address seemed to work.

I wanted to buy a few bucks more, but now I'm not sure if there is something wrong with the address I created. I'd be grateful for some guidance.

Best Answer

Ethereum wallet addresses are in hex [0-9A-F]*. While the address itself is case-insensitive (A is the same as a to the network), the case sensitivity is used as a (optional) checksum. It was built as an after-thought to an addressing scheme that lacked basic checksum validation.


The checksum works like so:

  1. lowercase address and remove 0x prefix
  2. sha3 hash result from #1
  3. change nth letter of address according to the nth letter of the hash:
  • 0,1,2,3,4,5,6,7 → Lowercase
  • 8, 9, a, b, c, d, e, f → Uppercase

So, you sha3 hash the address, and look at each Nth character of the sha result. If it's 7 or below, the Nth character in the address is lowercase. If it is 8 or above, that character is uppercase.

(Brought from an old Ethereum forum whose link is now broken.)

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