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

# RBF (Replace-By-Fee) transaction lifecycle

> Understand how Replace-By-Fee (RBF) replaces an unconfirmed transaction, how the original transaction's status changes, and the events you receive.

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## Overview

Replace-By-Fee (RBF) replaces an unconfirmed, already-broadcast transaction with a new version. This guide describes the full lifecycle of an RBF replacement: the replacement operations you can perform, how the original transaction's status changes, and the events you receive.

For the step-by-step operations, see [Manage transactions](/v2/guides/transactions/manage-transactions). For the fee rules that apply to RBF transactions, see [Estimate transaction fees](/v2/guides/transactions/estimate-fees#replace-by-fee-rbf-transaction-fee).

## Replacement operations

WaaS 2.0 supports the following RBF operations:

* **Speed up**: Replaces the original transaction with a higher-fee version so that it confirms faster. Use the [Speed up transaction](/v2/api-references/transactions/speed-up-transaction) operation.
* **Drop**: Replaces the original transaction with a version that effectively cancels it. Use the [Drop transaction](/v2/api-references/transactions/drop-transaction) operation.

Both operations apply only when the original transaction is in the `Broadcasting` status. They do not apply to transactions on the following chains: VET, TRON, TVET, SOL, and TON.

## Original transaction status after replacement

When a replacement transaction takes effect, the original transaction moves to the `Failed` status with the sub-status `ReplacedByNewTransaction`. For the complete list of statuses and sub-statuses, see [Transaction statuses and sub-statuses](/v2/guides/transactions/status).

## Chained replacements

Any subsequent drop or speed-up operations continue to apply to the original transaction. For example, if you create Transaction A, perform a drop operation on Transaction A using Transaction B, and then perform a speed-up operation on Transaction B using Transaction C, the speed-up operation still applies to Transaction A, not Transaction B.

## Events

RBF status changes are surfaced through the WaaS 2.0 transaction webhook events. Subscribe to the `wallets.transaction.updated` event, which covers the full transaction lifecycle including failure. For details, see [Webhook event types](/v2/guides/webhooks-callbacks/webhook-event-type).

## Related guides

* [Manage transactions](/v2/guides/transactions/manage-transactions)
* [Estimate transaction fees](/v2/guides/transactions/estimate-fees)
* [Transaction statuses and sub-statuses](/v2/guides/transactions/status)
* [Transaction sources and destinations](/v2/guides/transactions/sources-and-destinations)