Accounts Tree

A tree storing addresses and account (i.e. balances and further fields). This tree’s root is stored in each block’s header. The account tree can be used to verify that an account in a certain state was part of a certain block. And account tree is composed of account tree nodes using Ethereum’s Merkle Patricia Trie Specification.

Accounts and Transactions


Adding Accounts to the Accounts Tree


  1. subtract from all sender accounts
  2. add to all recipient accounts
  3. create contract accounts
  4. prune contract accounts (must be pruned when empty)

Position in tree is unrelated to position in block body.

Accounts Tree Nodes

An accounts tree node can be of two types: branch or terminal. Branch nodes build the tree structure while the terminal nodes are the leaves of the tree.

Accounts Tree Node Branch

The tree structure is composed of prefixes to decend and find the correct account in a terminal node. A branch is composed of a prefix and children:

Element Data type Bytes Description
type uint8 1 0
prefix length uint8 1  
prefix string length Common part of the hashes of all accounts on this side of the tree
child count uint8 1 Number of immediate tree sub nodes

And then for each child a structure as follows is attached:

Element Data type Bytes Description
child suffix length uint8 1  
child suffix string length Parent prefix + suffix compose new prefix
child hash Hash 32 Hash of part of the tree below

Accounts Tree Node Terminal

The terminal node is the leave node of the account tree, it contains the actual account.

Element Data type Bytes Description
type uint8 1 255
prefix length uint8 1 20
prefix string length The address of the account
account Account >= 9 The actual account, can be any kind