Base block heads: unsafe, safe and finalized

Last updated: September 22, 2026

At a glance

What you see

latest, safe and finalized return three different block numbers on Base, with finalized far behind. A block read at latest is sometimes replaced, while code that waits for finalized seems slow to react.

Why this happens

The OP Stack documentation defines the three states: unsafe — "the transaction is in a block whose data has not yet been posted to Ethereum", mapped to the latest tag; safe — the data is included in an Ethereum block that has not been finalized, mapped to safe; finalized — "Ethereum finalizes the block containing the data", mapped to finalized. Unsafe and safe rely on the sequencer and on Ethereum's ordering, while finalized relies on "Ethereum's consensus and finality guarantees". The OP Stack documentation also notes that OP Stack chains "do not have a public mempool": transactions go to the sequencer, which produces the unsafe blocks.

What to do

1. Use latest for fast, tentative UI updates, knowing the block can still change.
2. Use safe when you need the data to be posted to Ethereum.
3. Use finalized for irreversible actions such as crediting deposits.
4. Pass the tag explicitly on every read so related reads agree.

When this is not our problem

The three heads are defined by the OP Stack protocol and are reported the same way by every Base node, whoever operates it, Triport included. The distance between them is set by the sequencer and by Ethereum.