Antminer S21 Series: Solo Mining Setup on mkpool (2026)
Published
Share
Frequently asked questions
What is the mkpool stratum URL for an Antminer S21?
For Bitcoin it is stratum+tcp://btc.mkpool.com:3333 (vardiff). Set the worker name to your own Bitcoin address, optionally followed by a dot and a rig label, and set the password to x. Other SHA-256 chains use the same pattern on their own host, for example bch.mkpool.com, with the ports listed on each pool's connect page.
Do I need an account or to register the miner?
No. mkpool is account-less and non-custodial. The Bitcoin address you put in the worker field is both your identity and your payout destination, so any block the miner finds is paid to that address directly in the block's coinbase transaction. There is nothing to sign up for and no balance to withdraw.
Which difficulty port should an S21 use?
Use the vardiff port (3333). It starts low and automatically raises the share difficulty to match the S21's hashrate, which keeps share traffic sensible without any tuning. The fixed high-difficulty ports are meant for rented or aggregated hashrate such as NiceHash, which needs a set difficulty to report its full speed.
Do I need to enable AsicBoost?
No. Antminers use overt AsicBoost (version-rolling) automatically, and mkpool advertises version-rolling in its mining.configure handshake, so the two negotiate it without any setting. You do not gain anything by looking for an AsicBoost toggle; it is already in effect.
Can I use an encrypted (TLS or Stratum V2) connection?
Stock Bitmain firmware speaks plain Stratum V1 only. To encrypt the connection you need firmware that supports it, such as Braiins OS for Stratum V2, pointed at mkpool's TLS or Stratum V2 ports. The connection is otherwise identical; only the URL scheme and port change.
Can one Antminer mine more than one coin?
One miner mines one SHA-256 chain at a time, chosen by which host you point it at. You can switch between Bitcoin, Bitcoin Cash, BitcoinII, Bitcoin Cash II, DigiByte and eCash by changing the pool host and your payout address, but it hashes a single chain per connection. You can also set a different chain as a backup pool.
Why is my hashrate lower than the rated figure right after setup?
A freshly connected miner reports a rising average as it warms up and vardiff settles, so the first few minutes read low. Give it 10 to 15 minutes and compare the miner's own average hashrate against the pool's, which is estimated from your accepted shares and always lags real time. A persistent shortfall usually points to thermal throttling, a weak power supply, or a failing hashboard.
What password should I put in the pool configuration?
Use x. mkpool ignores the password by default; it only reads it when it carries options, such as d=1000000 to pin a static difficulty. The worker name field, not the password, is where your payout address goes.
Newsletter
Mining insights in your inbox
New guides, hardware reviews, and pool updates. No spam, unsubscribe anytime.
We use strictly necessary storage to run the site and, with your consent, anonymized Google Analytics to understand traffic. See our Cookie Policy.
The Antminer S21 family is the workhorse of home and small-farm solo mining in 2026: efficient enough to run at home, cheap enough per terahash to buy several, and fast enough that a single unit is a real lottery ticket against the Bitcoin network. This guide takes any S21, the base S21, the S21 Pro, the S21 XP, or a Hydro unit, from unboxed to submitting accepted shares on mkpool, paying straight to your own wallet.
Nothing here is mkpool-specific plumbing you have to trust. Solo mining on mkpool is non-custodial: you put your own Bitcoin address into the miner, and if it ever solves a block, the network pays that address directly in the block's coinbase transaction. The pool only relays work.
mkpool relays work and templates; the block reward is paid on-chain straight to the address you mine with.
Before you start
You need three things ready:
Power. An S21 draws roughly 3,500 watts; a Hydro unit more. Use a dedicated circuit rated for the load, the correct PSU or PDU, and a plug that matches your region's voltage. An S21 on an undersized circuit is the most common reason a first boot is unstable.
Network. A wired Ethernet connection to your router. The miner pulls an IP address over DHCP; you will need to find that address in a moment.
A wallet you control. Your own Bitcoin address, from a wallet whose keys you hold. Do not mine to an exchange deposit address, many exchanges do not credit coinbase (newly mined) transactions, and you would not hold the keys to a block reward anyway.
Step 1: Open the miner's web interface
Every Antminer is configured from a web page it serves on your local network. To reach it:
Connect the miner to your router by Ethernet and power it on.
Find its IP address. The easiest ways are your router's connected-devices list, or Bitmain's IP Reporter tool: run it, then press the IP-report button on the miner and it announces its address.
Type that IP address into a browser on the same network and log in. On stock firmware the default credentials are usually root / root.
⚠Change the default password first
A miner reachable at its factory password is a miner anyone on your network can redirect. Change it before you do anything else, in the Administration or System section of the web UI.
Step 2: Enter the mkpool stratum settings
Open Miner Configuration (sometimes labelled Pools or Settings). You will see three pool slots, each with a URL, a Worker and a Password field. Fill in Pool 1 for solo mining Bitcoin:
URL:stratum+tcp://btc.mkpool.com:3333
Worker: your Bitcoin address, optionally followed by a dot and a short rig name, e.g. bc1qexampleaddress.s21
Password:x
That is the entire trick. On a zero-fee, non-custodial pool the worker field is your account: the address identifies you on the dashboard and receives any block you find. The password is ignored unless it carries an option (more on that under difficulty, below).
Step 3: Add backup pools
Fill Pool 2 and Pool 3 as fallbacks with the same address, so a brief outage never leaves an expensive miner idle. Good choices are a different mkpool port, or even a different chain, for example:
Pool 2: a fixed-difficulty Bitcoin port (see the table below), same address.
Pool 3: another SHA-256 chain such as bch.mkpool.com with your Bitcoin Cash address, so the rig keeps hashing something useful if Bitcoin work is briefly unreachable.
The miner uses Pool 1 whenever it can reach it and only falls back down the list when it cannot.
Step 4: Choose the right port
mkpool exposes several Bitcoin stratum ports. They differ only in difficulty and encryption; all of them pay solo to your address. This table is generated from the live pool configuration, so these are the exact ports the pool is listening on right now:
For a single owned S21, use the vardiff port (3333). Variable difficulty starts low and automatically climbs to suit the miner's hashrate, which keeps the number of share submissions sensible without any manual tuning. If you run several units through one connection, or simply want fewer submissions, a fixed high-difficulty port also works, and those same fixed ports are what rented hashrate (NiceHash, MiningRigRentals, Braiins) must use, because a marketplace needs a set difficulty to report its full speed. The difference between the two is explained in vardiff vs fixed difficulty.
💡Pin a difficulty without changing ports
You can override difficulty from the password field on any port: set the password to d=1000000 (or any value) to request that static difficulty. This is the only thing mkpool reads the password for.
Mining a chain other than Bitcoin
An Antminer is a SHA-256 machine, so it can point at any of mkpool's SHA-256 chains, Bitcoin, Bitcoin Cash, BitcoinII, Bitcoin Cash II, DigiByte and eCash, one at a time. Change the host to that chain's *.mkpool.com address and use an address for that chain in the worker field. Each pool's connect page lists its own ports.
Step 5: Encrypt the connection (optional)
Plain Stratum V1 sends your address and the work in the clear. On a home network that is normally fine, but if you want it encrypted mkpool offers two options: Stratum V1 over TLS, and Stratum V2 over the Noise protocol. Both are in the table above.
›This depends on your firmware
Stock Bitmain firmware speaks plain Stratum V1 only. To use a TLS (stratum+ssl://) or Stratum V2 port you need firmware that supports it, for example Braiins OS for Stratum V2. If you run one of those, point it at the encrypted port from the table; the address and password stay identical. See Braiins OS and Stratum V2 for that path.
Step 6: AsicBoost is already on
Antminers use overt AsicBoost, better known as version-rolling, to hash a little more efficiently. mkpool advertises version-rolling in its mining.configure handshake, so the miner and pool negotiate it automatically the moment they connect. There is no toggle to find and nothing to configure, if you were looking for an AsicBoost setting, it is because there is nothing to do.
Step 7: Save, apply and verify
Save the configuration. The miner restarts its mining process and should connect within a minute. Now confirm it is actually working, from both ends.
On the miner, open the Status or Miner page and look for:
✓A healthy S21 shows
An average hashrate near the model's rating once it has warmed up (see the spec table below).
Accepted shares climbing, with rejects and stales near zero. Shares are proof of work, not payouts, they confirm the hashboards are doing valid work.
Chip temperatures in the normal band and fans spinning below their maximum.
All hashboards (usually three) present and contributing, not one reading zero.
On mkpool, open the Bitcoin dashboard and look up your address on the miners page, or go straight to your address page. Seeing your worker there with a live hashrate and a rising accepted-share count means the pool sees you and everything is wired up. The pool's hashrate estimate is derived from your shares and lags the miner's own readout by a few minutes; that is normal.
To sanity-check what a machine this size is actually up against, run its hashrate through the solo mining chance calculator.
Naming workers across a fleet
If you run more than one miner, give each a distinct rig name after the dot so you can tell them apart on the dashboard: address.s21a, address.s21b, and so on. The address before the dot stays the same, so every unit mines to the same wallet while reporting its own hashrate, temperature and share stats separately. That makes a dead or throttling unit obvious at a glance instead of hiding inside a combined total. Fleet strategy is covered in more depth in the fleet mining guide, which applies the same naming logic to any hardware.
Antminer S21 family at a glance
Published nominal specifications for the current air- and liquid-cooled S21 models. Exact figures vary by batch and firmware, so treat these as reference points and confirm against Bitmain's spec sheet for your unit.
Model
Hashrate
Power
Efficiency
Cooling
S21
200 TH/s
~3,500 W
17.5 J/TH
Air
S21 Pro
234 TH/s
~3,510 W
15.0 J/TH
Air
S21 XP
270 TH/s
~3,645 W
13.5 J/TH
Air
S21 Hyd
335 TH/s
~5,360 W
16.0 J/TH
Hydro
The efficiency jump from the S19 generation (roughly 29-34 J/TH) to the S21 family (13.5-17.5 J/TH) is one of the largest single- generation gains in SHA-256 mining, which is why an S21 is the current baseline for viable home solo mining.
Troubleshooting the first connection
No accepted shares. Re-check the URL scheme and port, confirm the worker really is your address (not a username), and make sure you did not accidentally set a TLS/V2 port on stock firmware.
Many rejects or stales. Usually a network or latency problem, or a fixed difficulty set far too low for an S21. Switch to the vardiff port and let it settle.
Hashrate well below rating. Check temperatures and power first, thermal throttling and an undersized supply are the usual causes, then look for a hashboard reading zero.
Worker not on the dashboard. If the miner shows accepted shares but the pool does not list you, confirm you are looking up the exact address you configured, on the matching chain's dashboard.
Antminer web-UI labels, default credentials and firmware capabilities vary by model and firmware version and are current as of July 2026; follow Bitmain's documentation for your exact unit. Hardware figures are manufacturer-published nominal specs and vary by batch. Nothing here is financial advice. Solo mining is probabilistic and can lose money depending on electricity cost and network conditions.
Mecanik1337Read →