> For the complete documentation index, see [llms.txt](https://docs.seismic.systems/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.seismic.systems/clients/python/chains/seismic-tx-type.md).

# SEISMIC\_TX\_TYPE

Protocol constant representing the transaction type byte for Seismic custom transactions.

## Overview

`SEISMIC_TX_TYPE` is the EIP-2718 transaction type identifier used by Seismic's custom transaction format. This byte prefixes all serialized Seismic transactions.

## Value

| Representation | Value  |
| -------------- | ------ |
| Hexadecimal    | `0x4A` |
| Decimal        | `74`   |

## Definition

```python
SEISMIC_TX_TYPE: int = 0x4A
```

## EIP-2718 Context

EIP-2718 introduced typed transaction envelopes to Ethereum. Transaction types are identified by a single byte prefix:

| Type   | Description                        |
| ------ | ---------------------------------- |
| `0x00` | Legacy transactions (pre-EIP-2718) |
| `0x01` | EIP-2930 (Access lists)            |
| `0x02` | EIP-1559 (Dynamic fee)             |
| `0x03` | EIP-4844 (Blob transactions)       |
| `0x04` | EIP-7702 (Set EOA account code)    |
| `0x4A` | **Seismic custom transactions**    |

## Transaction Format

A serialized Seismic transaction has the format:

```
[0x4A] + RLP([chainId, nonce, gasPrice, gas, to, value, data, ...])
```

Where `0x4A` is the `SEISMIC_TX_TYPE` prefix.

## Protocol Notes

* The SDK automatically sets this type for all shielded writes
* Seismic nodes recognize and process transactions with this type
* Standard Ethereum nodes will reject transactions with unknown types
* This type is part of the Seismic protocol specification

## See Also

* [UnsignedSeismicTx](/clients/python/api-reference/transaction-types/unsigned-seismic-tx.md) - Seismic transaction structure
* [sign\_seismic\_tx\_eip712](/clients/python/api-reference/eip712/sign-seismic-tx-eip712.md) - Transaction signing
* [ChainConfig](/clients/python/chains/chain-config.md) - Chain configuration with chain IDs
* [Shielded Write Guide](/clients/python/guides/shielded-write.md) - Guide to sending Seismic transactions


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