Sia Documentation
Navigating the V2 hard fork
What you need to know about the upcoming Sia fork
The Sia network is undergoing a hard fork to radically update the consensus code of Sia, providing significant benefits in performance, scalability, and functionality. Given the importance of this hard fork, we have started calling it Sia v2.
Updating to Sia v2 will be necessary for sending or storing coins, renting, or hosting after the fork. Every user, exchange, mining pool, wallet, and integration must update within the timelines outlined below.
How do I prepare for the fork?
If you are a host
Update to hostd version 2.1.0+.
If you are a renter
Update to renterd version 2.1.0+.
If you are using Sia-UI or siad
Update to walletd version 2.4.1+.
If you are using the Sia Central light wallet
You don't need to do anything to support the fork.
If you hold tokens on an exchange
We recommend moving your Siacoin to a self-storage wallet before the hard fork activation to ensure uninterrupted access to your Siacoin.
If you are an exchange or mining pool
Update to walletd version 2.4.1+. Read our upgrade guide for exchanges
How does it work?
Step 1: Software Release
If you haven't logged in for a while, in 2024 we divided Sia into three separate applications: renterd for renters who upload files, hostd for hosts who store those files, and walletd for Siacoin holders. You will need to download and install each application if you use the respective function. Sia-UI and siad are outdated and will not be updated.
The hard fork is multi-stage. First, users must signal support for the hard fork by updating to a fork-compatible version. Downloading this update means you are ready for the fork, even if the fork hasn't occurred yet.
Step 2: Activating the hard fork
The actual hard fork—the moment when you need to run a v2 node—will occur later in 2025. The Sia ecosystem is large, so we need to ensure that not only our users but also exchanges, miners, pools, web wallets, and other integrations have enough time to update.
The hard fork activates at block height 526,000 around June 6, 2025, at 06:00 UTC. After this height, blocks may contain v2 transactions, so if you are not using an updated node, you will not be able to sync. This will enable most of the new v2 features, but v1 blocks will still be allowed, giving those who lag behind a grace period to send their transactions to miners.
This grace period ends at block height 530,000 around July 4, 2025, 02:00 UTC. You need to update by this date to continue using Sia.
So what is the benefit of the hard fork...
...renters and hosts?
Sia v2 includes an update to the renter-host protocol, which has become faster and more efficient in almost all measurable aspects. Here are some key points:
Even more capabilities and flexibility for your contracts
Faster uploads and downloads, including simultaneous uploads to the same host
Enables decentralized uploading and downloading in the browser, requiring no plugins or daemons.
It is important for renters and hosts to update by June 6 to take advantage of v2 and the new renter-host interaction protocol as soon as possible.
...Siacoin holders?
Your Siacoins remain protected by your seed and are unchanged with Sia v2. walletd is fully compatible with existing blockchain data, so you do not need to move your coins to prevent loss. However, Sia v2 discontinues support for deprecated 28- and 29-word seeds in favor of the industry-standard BIP39 12-word seed phrases.
walletd only supports the new 12-word seed format and does not support the deprecated 28 or 29-word seeds. To ensure continuous access to your coins, we strongly recommend generating a new 12-word seed and transferring your balance. Use the SiaCentral web wallet to create a new seed and deposit address.
If you are using a synced Sia-UI wallet: First, send a small test amount (~10 SC) to the new address to confirm its receipt. Then transfer the remainder, leaving 1 SC, if necessary, to cover the network fee.
If you do not have a synced Sia-UI wallet: log into SiaCentral with the seed phrase of 28/29 words and transfer your coins from there. SiaCentral will continue to support both old and new seed phrase formats, but official applications will only support the new 12-word format.
We recommend all Siacoin holders update to walletd by June 6. After that, you will have a 1-month grace period for broadcasting transactions, but syncing new blocks will not be possible. Starting July 4, only software that supports signing transactions v2 will work—currently walletd and the SiaCentral web wallet. Sia-UI will not be updated.
If you hold Siacoins on an exchange, confirm that the exchange will support the fork. To ensure access to your tokens, we strongly recommend withdrawing them to a private wallet before the fork.
...for miners?
We have carefully designed Sia v2 to preserve the block header layout, so all mining hardware will remain compatible. However, you should check with your mining pool to ensure they are updated.
...for exchanges?
Sia v2 will significantly enhance performance and usability for your exchange. You will have more control over your Siacoin treasury and how to interact with it.
Exchanges must update to walletd v2 as soon as possible to ensure a smooth transition. Given the number of users you serve, you should allow time for proper updating. Once you do, your exchange will be able to support the fork as soon as it goes live.
Unconfirmed transactions from block 526,000 will remain available for mining until block 530,000, so normal operations can continue during the hard fork activation. If you are manually creating your transactions, you have the choice of when to switch from using v1 transactions to v2 transactions; we recommend waiting at least 6 blocks into the grace period before switching. This minimizes the chance that v2 transactions will be invalidated by a reorganization.
