> ## Documentation Index
> Fetch the complete documentation index at: https://base-a060aa97-docs-ia-overhaul-v2.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# 200ms Blocks

> Denim introduces native L2 blocks at a 200ms cadence, replacing Flashblocks with full standalone blocks at a faster cadence.

<Warning>
  **Flashblocks will be deprecated as part of this release.** Because native 200ms blocks deliver the same sub-second confirmation experience directly on the canonical chain, the Flashblocks WebSocket stream is no longer needed and will be removed. Migrate off the Flashblocks WebSocket stream before Denim activation.
</Warning>

## Motivation

Flashblocks expose sub-second updates but build within a single canonical block. Moving to native 200ms blocks eliminates that indirection: every 200ms interval is a full standalone block with its own number, hash, state root, and receipts, delivering the same sub-second confirmation experience directly on the canonical chain.

## What Changed

Ethereum block headers and `block.timestamp` remain in whole seconds. The BaseTime predeploy records the sub-second component before user transactions, while optional `timestampMs` and `blockTimestampMs` RPC fields expose the complete millisecond timestamp to applications and infrastructure.

## Migration

**Application developers**

Existing contracts and applications remain compatible. Use the BaseTime `timestampMs()` getter when contracts need same-block millisecond precision; continue using `block.timestamp` when second-level precision is sufficient.

**RPC and indexing providers**

Support the optional `timestampMs` block and header field and `blockTimestampMs` on mined transactions and logs. Do not infer millisecond timestamps from the whole-second header value.

**Node operators**

Upgrade to a Denim-compatible release before activation. Plan capacity for the higher native block rate across execution, storage, RPC events, and peer-to-peer propagation.