At the below line:


The attribute "solid" is set in the transaction. Tracing this back to the transactionValidator:


It looks like it is checking out whether the Trunk and Branch transaction are also solid? Is that all there is to it?

Maybe the better way to ask this is: What does solidity mean in this context?

1 Answer 1


A transaction is considered solid on your node when

  • it exists in your local database and
  • its trunk and branch are also either solid or the NULL_HASH

Effectively, this means that the transaction itself is present and you can walk from that transaction towards the root (the initial milestone which has NULL_HASH both for trunk and for branch) in any way you like, without reaching transactions that are unknown to your node.

In a fully synchronized node, all transactions are solid. When a transaction is not solid, your node will ask its neighbors for the missing puzzle pieces.

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