Short answer (3 November 2026): since 8 August 2026, a Bitcoin Knots node may follow a different chain from the one Bitcoin Core and mempool.space follow. Which chain yours is on depends on the Knots version and on whether you accepted BIP-110. To find out, ask your node for the hash of block 961640 and compare it with mempool.space. Until you have done that, don't send, receive or open Lightning channels with a wallet that relies on that node.
Our Bitcoin Core vs Knots comparison covers the background. This page is the hands-on check. We quote each side in its own words and call the networks the SHA256d chain, the BIP-110 chain and the BLAKE2b chain.
What happened, in two steps
- 8 August 2026: the BIP-110 split. BIP-110, the "Reduced Data Temporary Softfork", required blocks 961632 to 963647 to signal for it, and nodes enforcing it rejected blocks that did not. Knots 29.3 shipped it in May 2026 behind an explicit confirmation. Most SHA256d mining power kept producing blocks that did not signal. The pull request that closed BIP-110 says it "split to a new chain and stalled" (BIPs PR #2245), and Bitcoin Optech called it an "unsuccessful activation attempt".
- 2 September 2026: Knots 29.4.1 and the BLAKE2b hard fork. Knots 29.4.1 switches the proof of work from SHA256d to BLAKE2b at block 961640 and applies the BIP-110 rules from that height. Its release notes call it "a backward-incompatible protocol change". bitcoin-blake2b.org dates the first BLAKE2b block, 961640, to 30 August 2026.
The two sides describe the result in opposite terms. Knots' 29.4.1 release notes call the SHA256d chain "a new altcoin launched by former miners" and the events of 8 August "the biggest attack on the Bitcoin network to date". bitcoin-blake2b.org, the site those notes link to, says the BLAKE2b rules keep Bitcoin "as money only". The BIPs repository, which now lists BIP-110 as Closed, and Bitcoin Optech describe the same events as an activation that failed and a chain that "stalled". Bitcoin Core and mempool.space stayed on the SHA256d chain.
Which chain each version follows
| What you run | Chain it follows |
|---|---|
| Bitcoin Core, any version | The SHA256d chain |
| Knots 29.3.knots20260507 or older (no BIP-110 enforcement) | The SHA256d chain |
| Knots 29.3.knots20260508 or 29.4, BIP-110 accepted | The BIP-110 chain, which split off and stalled. A Knots pull request opened in mid-August describes it as "crawling with only one block every few days" (knots#358) |
| Knots 29.3.knots20260508 or 29.4, BIP-110 not accepted | Run the check below |
| Knots 29.4.1, 29.4.2 or 29.4.3 | The BLAKE2b chain, with no opt-out: "there is no longer a way to run this software without the rules it enforces" (knots#362) |
One consequence is easy to miss: updating Knots to 29.4.1 or later moves a node to the BLAKE2b chain. According to bitcoin-blake2b.org, a node coming from Core or older Knots usually "walks back to the fork, and then downloads the BLAKE2b chain". Whichever chain you want, check the version before you update.
How to check your node
Steps 2 to 4 use standard RPC commands, documented in the Bitcoin Core RPC reference, and Knots has them too. Run all four steps where your node runs.
1. Which software. bitcoind -version prints the client name and version.
2. The hash test. Ask your node for the hash of block 961640, which comes after the split:
bitcoin-cli getblockhash 961640
On the SHA256d chain, block 961640 is 00000000000000000001d82da6ecccf08e07afa383f9212b0e1b95cc72430c00 (mempool.space and blockstream.info, checked 3 November 2026). You can look it up yourself at mempool.space/api/block-height/961640.
3. Height and tip.
# "blocks" is your node's height, "bestblockhash" its tip
bitcoin-cli getblockchaininfo
# the tip on its own
bitcoin-cli getbestblockhash
Compare "blocks" with the latest block on mempool.space (974,413 when we checked on 3 November 2026).
4. Which rules your software carries.
bitcoin-cli getdeploymentinfo
In the Knots source code, 29.4.1 and later return a top-level "blake2b" entry with "height": 961640. Versions 29.3.knots20260508 and 29.4 list a deployment called "reduced_data", which is BIP-110, and have no "blake2b" entry. Bitcoin Core 32.1 has neither. This tells you what your software is built to enforce, not which chain it ended up on.
Reading the result:
- Same hash at 961640, and your height within a block or two of mempool.space: your node is on the SHA256d chain.
- "Block height out of range", or a height far below mempool.space's that barely moves over an hour: if the node is not still doing its first sync, it is most likely on the stalled BIP-110 chain.
- A different hash at 961640, and a height that keeps growing: your node is on another chain. With Knots 29.4.1 or later, that is the BLAKE2b chain.
If you run the Bitcoin Knots app on Umbrel
The Bitcoin Knots app on Umbrel is at version 1.2.13, which runs Knots v29.4 and was last updated on 8 August 2026. Its release notes say it "adds BIP 110 code" and "requires you to accept or switch to another version directly on the Umbrel UI". If you accepted, the node enforces BIP-110 without the BLAKE2b change, so going by the table above it would be on the stalled BIP-110 chain. We have not tested that on a live Umbrel.
Umbrel's built-in terminal is under Settings > Advanced settings > Terminal. Choose App, then Bitcoin Knots, to get a shell inside the app's container (Umbrel support). We have not run bitcoin-cli there ourselves. If it cannot connect, the app's connection details show the RPC username and password. Our Umbrel vs Start9 comparison covers both platforms.
Before you move any funds
- Check first. A wallet connected to your node sees only the chain the node follows, so don't move funds with it until you know which chain that is.
- Coins from before the split exist on both chains, and a payment can be copied from one to the other. bitcoin-blake2b.org says: "A spend of the same coins can be copied onto the other chain if it is signed the ordinary way." Its FAQ describes a new opt-in signature type, SIGHASH_UNIFIED (knots#357), and calls the protection it gives "incidental to the new message, one-way, and per signature". We have not tested it or checked wallet support, so this page gives no steps for splitting coins.
- Lightning follows the node. If LND or Core Lightning runs on your Knots node, check the chain before you open, close or pay through a channel.
- Choose the chain, then the software. For the SHA256d chain, run Bitcoin Core. Our lesson on setting up a Bitcoin node walks through it. For the BLAKE2b chain, bitcoin-blake2b.org points to Knots 29.4.2, and the latest release is 29.4.3 (28 October 2026). Before you switch in either direction, back up your wallet, and the data directory too if you have the space. We have found no documentation for taking a data directory back from the BLAKE2b chain to Bitcoin Core, so expect a full re-sync.
Frequently Asked Questions
Is my Bitcoin Knots node still on the same chain as Bitcoin Core?
It depends on the version and on what you accepted. Knots 29.3.knots20260507 and older follow the SHA256d chain, like Bitcoin Core. Knots 29.3.knots20260508 and 29.4 with BIP-110 accepted follow the BIP-110 chain, which split on 8 August 2026 and stalled. Knots 29.4.1 and later follow the BLAKE2b chain. Compare your node's hash for block 961640 with mempool.space to be sure.
How do I check which chain my node is on?
Run bitcoin-cli getblockhash 961640. On mempool.space that block is 00000000000000000001d82da6ecccf08e07afa383f9212b0e1b95cc72430c00 (checked 3 November 2026). If they match, your node is on the SHA256d chain. If you get "Block height out of range", or your height is stuck far behind mempool.space's, it is most likely on the stalled BIP-110 chain. A different hash with a growing height means another chain, which on Knots 29.4.1 or later is the BLAKE2b chain.
Is it safe to send bitcoin from a Knots node right now?
Not until you have checked which chain the node is on. Coins from before the split exist on both chains, and bitcoin-blake2b.org warns that "A spend of the same coins can be copied onto the other chain if it is signed the ordinary way." A payment you make on one chain may also happen on the other.
What does the Bitcoin Knots app on Umbrel do?
Version 1.2.13 of the app runs Knots v29.4. Its release notes say it "adds BIP 110 code" and ask you to accept it or switch to another version in the Umbrel interface. If you accepted, we would expect the node to be on the stalled BIP-110 chain, though we have not tested that on a live Umbrel. Run the hash check to be sure.
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