> ## Documentation Index
> Fetch the complete documentation index at: https://docs.optimism.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Lost pre-regenesis data

> Understand why some OP Mainnet transaction data from January to July 2021 cannot be fully recovered.

This page explains why part of OP Mainnet's earliest transaction history is permanently incomplete.
For how to look up the pre-regenesis history that *is* available, see [accessing pre-regenesis history](/op-mainnet/pre-bedrock-history/regenesis-history).

Because of the final regenesis on 11 November 2021, transactions from before that date are not part of the current blockchain and do not appear on [Etherscan](https://explorer.optimism.io/?utm_source=op-docs\&utm_medium=docs).
Most of that history remains queryable through external tools, but one early slice of it was lost.

## Lost data directories

Three data directories that were used by legacy L2Geth Sequencer instances
during the period of January 2021 to July 2021 had been errantly deleted during
an infra cleanup in August 2023.

These data directories contained information about the effects of transactions,
once executed. This information can only be obtained by properly executing the
transaction chain. The most valuable data within these directories was (1) events
emitted by smart contracts during each transaction and (2) the success state of
the transaction (whether or not the transaction executed or reverted). This
information is valuable for tracking things like ETH transfers or ERC-20 token
transfers. Without this we can still know the final set of balances but the
intermediate balances become opaque.

The transaction data for this period of time was published to a smart contract
on Ethereum called the [CanonicalTransactionChain](https://etherscan.io/address/0x5e4e65926ba27467555eb562121fac00d24e9dd2).
While it is theoretically possible to recover the data by downloading and
re-executing this chain of transactions from Ethereum, this is a labor intensive
and costly task that may not fully recover the data. The OP Labs team did
attempt data recovery efforts, including reaching out to several partners.

## Impact

No state, balances, or user assets were lost. Most of the impact is felt by data
providers who want complete data sets for analysis purposes and by individuals
who may want this information for tax purposes.

Since this was very early during the history of OP Mainnet there are relatively
few transactions in this period and this data is infrequently requested. Most
requests for this data came from individuals who needed access to this information
for the 2021 tax season though this is mostly no longer relevant today (many
people who needed this data already retrieved it).

## Going forward

We recognize the inconvenience this has caused some of our community and their
users and we're sorry for the frustrations. In an effort to prevent similar
situations from happening again in the future, we are evaluating and updating
existing processes and frameworks.