Missed the Hard Fork(s)?

There have been several hard forks in Sia network's lifetime. Most recent one happened on June 6th, 2025 and upgraded Sia to its 2.0 version.

Sia 2.0 marks an important milestone in the network's history and its biggest update so far. Not only you will be using Sia through a new and more performant set of apps, each named after its purpose, but Sia is also migrating its blockchain to a new and more efficient format allowing instant syncing and opening doors for a lot of new applications.

What changed?

This hardfork has introduced Utreexo (see details below), making Sia the world's first Utreexo-native blockchain. It comes with many benefits that are crucial for Sia to scale and to deliver a truly decentralized storage network without compromises.

What is Utreexo?

Today, blockchains are not just a full transaction history of the network but each block also contains a state, the data needed to validate new blocks. This is huge and evergrowing pile of data. And even if you dropped the whole history, the state required to validate a Sia block is very large, probably close to a few GB.
Blockchains also have an enormous databases of UTXOs (unspent transaction outputs) that Utreexo replaces with simple accumulator that provides same core functionality is a database: it lets you add new elements and it lets you ask if some element is present or not. It does even better as it doesn't let you remove an element, which fixes potential consensus issues of other blockchains.
Utreexo changes the way we design and implement blockchains by separating the transaction history from state which reduces its size down to few Kb.
This allows new users to skip the long syncing process by downloading one of these states from a peer (or an explorer) very quickly and fast forward to a particular "checkpoint" that is used to initialize the new Sia node.

Want to learn more?

Sia Blog: Utreexo in Sia: A Summary (2021)
Luke Champine: Utreexo in Sia: An Overview (2021)
Luke Champine: Utreexo in Context (2022, MIT Bitcoin Expo)
Luke Champine: Actually Functional Blockchain Design (2024, Lambda Conf)

Sia software went through radical overhaul over last few years, bringing huge performance, scaling and user experience upgrades. Sia-UI is now deprecated and instead there is a new set of modern looking apps, each with its own purpose: walletd for wallet users, renterd for renters, hostd for hosts and explorerd for exchanges or mining pools.

Main advantage of Utreexo is in how vastly easier it is to join the network as a full node. Previously you couldn't do anything until you finished syncing. That process took days and in same cases even more than a week as the main bottleneck was your HDD and if you didn't have SSD it took way too long. With 2.0, not only can you download the state of network in form of few Kb, but you can also download individual blocks in parallel, taking the full sync time down to under an hour. The main bottleneck in 2.0 is mostly your internet bandwidth which means that with a good connection this could even get down to minutes.

It also opens door for existence of many new features and tools like the lite node (see detail below), or indexer which will let people use a 3rd party to manage their contracts (no more details known at time of writing).

What should I do?

This information is for those who miss/missed the July 4th and want to know what options they have left.

Both renters and hosts should update to latest versions (of renterd and hostd) and then re-sync.

As a renter you probably already lost all of your data and need to re-upload them.

As a host you probably failed a bunch of contracts, affecting your host reputation. You will need to decide if it's better to start a new host (identity). Reputation affects the rate at which renters select your host, so this shouldn't be underestimated.

Follow the instructions on the official site for Hosts & Renters

Wallet users:

What is the difference between a seed, wallet and a wallet address?

Seed and wallet are basically the same things:

wallet is an abstract representing something that can hold your coins
seed is a private key that lets you (or anyone else who has it) to access and manage your coins, meaning that each 1 unique seed always loads the same wallet.

Keep in mind that wallets are not stored on any server (unlike your bank accounts). The balance you see is based on a local process during which your wallet app checks every single transaction on the network if it matches your seed's signature, writes them down and then displays the balance as a sum of all of your incoming and outgoing transactions.

This process requires your wallet application to be fully synchronized, because the wallet app can show you only results based on the data it knows. Partial synchronization may result in all or some of your transactions to be not visible and your balance to be incorrect until you're fully synced.

wallet address is an address that you can use to receive coins to your wallet. One wallet can have many wallet addresses and no matter which one of them you will use, the received coins will always belong to your wallet.

If you forget your wallet address, that's ok. You don't even have to remember it, because it can be easily generated again or you can just easily generate another one.

Only thing that you need to remember is your seed. If you lose it, you lose access to your coins and no one can help you.

I have 28/29 word seed

The only wallet currently accepting 28/29 word seeds is the Sia Central Lite Wallet. It works for both Siacoin (SC) and Siafund (SF) and you can find it here.

Create new wallet and generate a wallet address

Use Sia Central Lite Wallet (or walletd) to create a new wallet and securely store the displayed 12-word seed. If you lose it, no one can help you.
Click Receive and copy the wallet address.

Load your old wallet with 28/29-word seed

Use Sia Central Lite Wallet to load your old wallet from the 28/29-wird seed. Sia Central is a multi-wallet so you can handle the entire migration in single place.
Click Send and paste in the wallet address you copied in previous step. Make sure that first few and last few characters are the same and it is the same address. Then confirm it and check the new wallet in few minutes, the incoming transaction should appear.
If you cannot see your transactions, check the options and increase the "Address Lookahead" to something like 500 000.

Migration done!

After seeing the coins in the new wallet you've successfully finished the migration. Make sure your new seed is securely saved and it's still a good idea to also keep the old seed as you never know when you accidentally send coins to it out of a habit.
If you cannot see the incoming transaction, give it few minutes. And if you are using walletd, you will see the transaction only after being 100% synced.

Remember that the seed you just made is to be used with the "wallets" only, like walletd or Sia Central Lite Wallet. If you ever decide to start renting or hosting, please make a new seed for that purpose, because renting/hosting both uses only the wallet address at first index.

I have 12 word seed

You don't have to do anything. You're ready!

I have Ledger HW Wallet

You don't have to do anything else, just update your Sia app from the Ledger App Catalog and you're ready!
If you cannot see transactions, set the starting block height to 0, hit the re-scan button and wait a bit.

I have my coins on an exchange

Your exchange should have upgrade but if that's not the case, you need to contact their support as they are ones holding your coins. Not your keys, not your coins.

What wallet should I use?

Basically you have three options:

If you want to be your own master, run your own walletd node (wallet app with an entire copy of blockchain). Be prepared that synchronization can take some time.
If you are in a hurry, use Sia Central Lite Wallet. You're still in control (your seed is encrypted in the browser's cache and never leaves your computer), but you skip the blockchain synchronization as the server operator (Sia Foundation) is running already synced blockchain it reads from, resulting in instant access to your coins.
If you want to use hardware wallet for its secure seed management and very convenient usage, try Ledger HW Wallet. It's currently not available on Ledger Live, but both the walletd and Sia Central Lite Wallet support it. See a detailed guide in the official Sia Docs.

Where can I download the wallets?

We're intentionally not sharing any links. Clicking links on the internet without any awareness is fastest way to get scammed. We believe it's a good practice to educate the users by making them find the downloads themselves.

You can find all of the wallets on Sia's website, which is sia.tech:

lite wallet: https://sia.tech/community?category=wallets (scroll down)
walletd: https://sia.tech/upgrade-your-software

If you decide to get a Ledger HW Wallet, you can find it in many stores - just make sure you buy a new and sealed one.

Keep in mind that Sia Foundation will never force you to update your wallet and no matter what, your coins are safe. But there will be many who might try to pressure you into a download of a malicious wallet - don't trust these emails or private messages and if not sure, you can always visit the official Sia discord and ask the devs and community directly.

In truly decentralized systems, the updates are voluntary and manual installation of an update is basically a voting process. For example, if the developers ever made some malicious update, users could decide to NOT install it and stay on the old version, still functioning perfectly. It's a part of the platform's immunity and self-defense system, being resistant to ill-intended changes. If you're interested in this, see how an attempt for a hostile corporate takeover, known as SegWit2x, played out for Bitcoin in 2017.

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