Antminer S21+ Solo Mining Setup Guide (2026)

The Bitmain Antminer S21+ is a 235 TH/s SHA-256 ASIC, one of the most capable air-cooled miners you can point at SoloFury. Setting it up for solo mining takes about 15 minutes, and the process is the same for all five coins: open the miner’s web interface, enter a SoloFury stratum URL with your wallet as the worker name, and confirm shares are arriving. This guide walks through each step, plus per-coin ports, the optional encrypted connection, firmware, and verification. (Curious what the stratum protocol actually does — and what V2 will change for miners? See Stratum V2 vs V1.)

If you run an S19, S19 Pro, S19 XP, or a Whatsminer M50/M60, use the Antminer S19 & Whatsminer Setup guide instead — the interface differs slightly.

Key Takeaways

• Four steps: open the web interface, set the SoloFury pool, pick your coin, and verify on the dashboard.
• Worker name is wallet.label. BCH and BCH2 need their CashAddr prefix (bitcoincash: / bitcoincashii:), XEC needs ecash:.
• AsicBoost is automatic and already in the S21+‘s 16.5 J/TH rating — there is nothing to enable.
• Run Normal (stock) power mode for solo. The real efficiency lever is undervolting with custom firmware, not power mode.
• Pick the closest region (Atlanta, Frankfurt, or Singapore); add TLS if you want the connection encrypted.

What do you need before you start?

The S21+ is an industrial machine — confirm the basics before powering on.

• Power: a dedicated 220–240V circuit; the S21+ draws about 3,877 W (roughly 17 A at 240 V), so size the breaker accordingly (a 20 A circuit with headroom). Standard 120 V household outlets are not sufficient.
• Network: wired Gigabit Ethernet with DHCP or a known static IP.
• Cooling and noise: about 75 dB at one meter and a large volume of hot exhaust — plan for a ventilated, non-living space and keep ambient temperature under 30°C.

Step 1 — How do you access the miner’s web interface?

Connect the S21+ to your network, find its IP address (check your router’s DHCP client list, or use Bitmain’s APMinerTool / IP Reporter on the same network), and open http://<asic_ip> in a browser. Default credentials are usually root / root.

Step 2 — How do you configure the SoloFury pool?

In the Antminer web interface, go to Miner Configuration → Pool Settings. The S21+ has three pool slots; point them at your closest SoloFury region across its three ports for automatic failover.

A BCH example, using your wallet plus a worker label as the username:

Pool 1:  stratum+tcp://eu-bch.solofury.com:7070
Pool 2:  stratum+tcp://eu-bch.solofury.com:7071
Pool 3:  stratum+tcp://eu-bch.solofury.com:7072
Worker:  bitcoincash:qz...your_BCH_address.S21Plus01
Password: x

The eu- prefix above is the Europe example; swap it for your region (no prefix for the Atlanta primary, asia- for Asia-Pacific). The password field is unused in solo mining — any value works.

Step 3 — Which coin do you want to mine?

The S21+ can mine any of SoloFury’s five coins; only the hostname and port change. Use the matching pair below, and add your region prefix (eu- or asia-) as needed.

Because the S21+ switches coins with just a pool-URL change, you can follow difficulty windows across chains — check live difficulty on the Network Radar to decide when a switch is worth it.

Do you want an encrypted (TLS) connection?

TLS Stratum encrypts the link between your miner and SoloFury, protecting your worker name and share data on the network path. It does not change your hashrate or odds — it is a privacy and integrity layer. SoloFury supports TLS natively on every coin, using the plain port plus 10,000 (so BCH’s 7070 becomes 17070) with the ssl:// scheme:

Pool 1:  stratum+ssl://eu-bch.solofury.com:17070
Worker:  bitcoincash:qz...your_BCH_address.S21Plus01
Password: x

Not every firmware supports TLS, and the exact endpoints and steps are in the dedicated TLS Stratum Mining guide — start there if you want an encrypted connection.

Step 4 — What firmware and power settings should you use?

The S21+ ships with Bitmain stock firmware and also runs several aftermarket options.

AsicBoost (version-rolling) is automatic on the S21+ and already included in its 16.5 J/TH rating — there is nothing to switch on, and SoloFury negotiates it on every coin. It is not an extra efficiency knob; to confirm it is active, see the AsicBoost guide.

Custom firmware — Braiins OS+ (open-source, free, with detailed per-chain monitoring), Vnish, and LuxOS (closed-source, auto-tuning) are all compatible with SoloFury. Their real benefit is undervolting and per-board tuning, which can lower power at the same hashrate; see the Undervolting Antminer S21+ guide.

Power mode — use Normal (stock) mode for solo mining. It is the right balance of hashrate and reliability; pushed modes spend extra electricity for a marginal lottery edge, and low-power mode reduces your exposure. Weigh the trade-off for your electricity rate with the Profitability Calculator.

Step 5 — How do you verify the connection?

After saving, wait one to two minutes, then confirm from both sides.

On the miner itself, check that the pool shows Connected and the accepted-share count is rising, with no rejected or invalid shares in the first few minutes. On the SoloFury side, open the dashboard and search your wallet — your S21Plus01 worker should appear within a minute or two. Reported hashrate looks low at first because vardiff is still converging, then climbs toward spec over 15–30 minutes.

If anything looks off, the Miner Health Check guide walks through the diagnostics, and Reading Your Worker Stats explains each dashboard metric.

How do you name workers across a fleet?

If you run several S21+ units on one wallet, give each a distinct label so the dashboard stays readable: S21Plus01, S21Plus02, S21Plus03, and so on. With a clear convention, an anomaly is obvious at a glance — if every worker is fine but S21Plus03 is missing, you know exactly which machine to check. Comparing identical units side by side is also the most reliable way to spot an underperformer, as covered in the Miner Health Check guide.

Hardware Specifications

For more efficient siblings, the S21 Pro (around 15 J/TH) and S21 XP (around 13.5 J/TH) follow the same setup process — only the spec numbers differ.

Troubleshooting

If the worker does not appear within a few minutes: re-check the stratum hostname and the port for your coin (they differ — see Step 3), confirm the wallet username has the correct prefix, and make sure the miner can reach the network. If shares flow but hashrate or reject rate looks wrong, switch to your closest region and see the Miner Health Check guide.

Frequently asked questions

What is the SoloFury stratum URL for an Antminer S21+? Use stratum+tcp://<coin>.solofury.com:<port> for your closest region, where the coin and port match the table in Step 3 (for example BCH on 7070). Add the eu- prefix from Europe or asia- from Asia-Pacific. The worker name is your wallet followed by a dot and a label.

Do I need to enable AsicBoost on the S21+? No. Version-rolling AsicBoost is automatic and already included in the S21+‘s 16.5 J/TH rating, and SoloFury negotiates it on every coin. You can verify it is active using the AsicBoost guide, but there is nothing to switch on.

Which power mode should I use for solo mining? Normal (stock) mode. It balances hashrate and reliability. Pushed modes waste electricity for a marginal lottery edge, and low-power mode reduces your exposure — only deviate if your electricity rate clearly justifies it.

Can one S21+ mine all five SoloFury coins? Yes. Change the pool hostname and port to the coin you want (and use a wallet in that coin’s format). The miner reconnects in seconds, with no extra fee and no downtime beyond the reconnect.

Does the S21+ support TLS to SoloFury? Yes, if your firmware does. SoloFury’s TLS endpoints use the plain port plus 10,000 (BCH 17070, and so on) with the ssl:// scheme. See the TLS Stratum Mining guide for details.

Why is my hashrate below 235 TH/s right after setup? Vardiff starts low and converges over the first 15–30 minutes, so early dashboard readings understate your real hashrate. If you are still well below spec after 30 minutes, run the Miner Health Check diagnostics.

Should I install custom firmware? It is optional. Braiins OS+, Vnish, and LuxOS can lower power at the same hashrate through undervolting, which improves your cost per terahash — but stock firmware mines on SoloFury perfectly well. Back up your config before flashing anything.

What password should I use in the pool config? Any value — x is conventional. In solo mining the password field is not used, so it does not matter what you enter.

Next Steps

• Open the SoloFury dashboard to monitor your worker live.
• Run a Miner Health Check after 24 hours to compare actual versus expected performance.
• Compare which coin gives the best return for your hashrate with the Profitability Calculator and the Network Radar.
• Want an encrypted connection? Follow the TLS Stratum Mining guide.