Connection & SecurityIntermediate10 min read

Which Stratum Port and Difficulty Should You Use? (2026)

Published July 24, 2026

Every mkpool chain exposes several stratum ports, and the difference between them is difficulty and encryption. The difficulty choice confuses people more than it should, partly because of a common myth that a higher difficulty means a better chance of a block. It does not. This guide explains what share difficulty actually is and gives you a one-line answer for your hardware.

Share difficulty is not network difficulty

There are two different difficulties in play, and keeping them apart is the whole point:

Network difficulty is how hard it is to find an actual block. It is set by the blockchain and is the same for everyone. Finding a hash that beats it is the win.
Share difficulty is a much lower bar the pool sets so your miner can prove it is working. A share is a hash that beats the share difficulty. Most shares are nowhere near a block; they are just evidence of hashing.

Your miner submits a share every time it finds a hash meeting the share difficulty. Raise that difficulty and shares are rarer but each represents more work; lower it and shares are frequent but lighter. Either way the pool multiplies share difficulty by share count to estimate your hashrate.

The key point

Share difficulty changes how often you submit shares, not your odds of a block. A block is found when one of your shares happens to also beat the network difficulty, and that can land on any share, on any tier. Your real odds depend only on your hashrate versus the network, which you can check with the chance calculator.

Vardiff vs fixed

mkpool offers two kinds of port:

Vardiff (variable difficulty) starts low and automatically tunes your share difficulty up or down to hold a sensible submission rate as your hashrate changes. Point a Bitaxe and a 300 TH/s ASIC at the same vardiff port and each settles at the right difficulty on its own.
Fixed difficulty pins the value and never moves it. That is what a hashrate marketplace needs, because it sends a large, constant amount of work and reports a fixed speed.

Here are mkpool's live Bitcoin ports. The table is generated from the pool config, so the difficulties and ports are exactly what the pool is serving:

Host: btc.mkpool.com

Port	Difficulty	Encryption	Rented hashrate
3333	vardiff [1024 to 1M]	Plain	Owned miners
3334	vardiff [1024 to 1M] · TLS	TLS	Owned miners
3335	fixed 1,000,000 · TLS	TLS	Owned miners
3336	fixed 10,000,000 · TLS	TLS	Owned miners
3342	fixed 50,000,000 · TLS	TLS	Owned miners
3337	fixed 1,000,000	Plain	NiceHash · Braiins
3338	fixed 10,000,000	Plain	NiceHash · Braiins
3339	fixed 50,000,000	Plain	NiceHash · Braiins
3340	vardiff [1024 to 1M]	Stratum V2	Owned miners · Braiins
3380	fixed 1,000,000	Stratum V2	Owned miners · Braiins
3381	fixed 10,000,000	Stratum V2	Owned miners · Braiins
3382	fixed 50,000,000	Stratum V2	Owned miners · Braiins

Stratum V2 URL: stratum2+tcp://btc.mkpool.com:3340/9c9aZWzETaiJyqGGUSCn8GqFgTpxs96ert4d4jGeRnvxqRqhZar

Every other chain follows the same shape on its own host; the exact numbers differ because Scrypt and Equihash chains use different native difficulty scales. Each chain's connect page shows its own ports.

Which port for your setup

A Bitaxe, NerdQAxe or other small board

Use the vardiff port. Variable difficulty starts low so the first shares arrive within seconds, useful confirmation that the board is really hashing, then settles as it learns your rate. There is nothing to set.

One or a few ASICs you own

Vardiff still works perfectly for a single Antminer S21 or a small stack. If you would rather cut the number of share submissions, for example running several units through one connection, a fixed high-difficulty port is a fine choice too. Neither changes your block odds; it is purely about share traffic and how smooth your hashrate graph looks.

NiceHash, MiningRigRentals or Braiins

Use a fixed high-difficulty port, the ones marked for rented hashrate in the table. A marketplace pushes a large, steady load and needs a set difficulty to report its full advertised speed. On vardiff it would either flood the pool with shares before the difficulty ramps, or under-report while it settles. Renting hashrate is covered end to end in NiceHash solo mining.

Match the tier to the rented speed

If you rent, say, 500 TH/s, a difficulty pinned far too low will bury the connection in shares and can look like rejects or lag. Start at the highest fixed tier the pool offers and step down only if you see very few shares.

Pinning a custom difficulty

You do not have to switch ports to change difficulty. On any port, set the password to d=NNNN, for example d=1000000, and mkpool pins your share difficulty to that value. This is the only thing the password field is used for, and it is handy for testing or for a device whose firmware will not let you reach a particular port.

Encryption is a separate choice

Notice in the table that TLS and Stratum V2 ports come in the same vardiff and fixed flavours as the plain ports. Difficulty and encryption are independent: pick the difficulty that suits your hardware first, then pick the plain, TLS or Stratum V2 port at that difficulty. Encrypting the link does not change any of the difficulty advice above.

If your hashrate graph looks jumpy

A very low share difficulty on a fast miner, or simply a short averaging window, makes the pool's hashrate estimate bounce around. That is normal and not a fault. Let vardiff settle, and read the longer-window figures rather than the instantaneous one, how to interpret all of them is in reading your worker stats.

Disclaimer

Port numbers and difficulty ranges are read live from the pool config and are current at the time of reading. Nothing here is financial advice. Solo mining is probabilistic and can lose money depending on electricity cost and network conditions.

Frequently asked questions

Does a higher share difficulty improve my chance of finding a block?

No. Your probability of finding a block depends only on your hashrate relative to the network, not on the share difficulty the pool assigns you. Share difficulty only changes how often your miner submits a share and how smooth your hashrate estimate looks. A block is found when a share happens to meet the full network difficulty, and that can happen on any share regardless of the tier you are on.

What is the difference between vardiff and fixed difficulty?

Vardiff (variable difficulty) starts low and automatically raises or lowers your share difficulty to keep the submission rate sensible as your hashrate changes. Fixed difficulty pins it to a set value that never moves. Vardiff is best for owned hardware; fixed is for rented or aggregated hashrate that reports a constant speed.

Which port should a Bitaxe or NerdQAxe use?

The vardiff port. A small miner benefits most from variable difficulty, which starts low so shares come in quickly and confirm the miner is working, then settles as it learns your hashrate. There is nothing to configure.

Which port should I use for NiceHash or rented hashrate?

A fixed high-difficulty port. Hashrate marketplaces send a large, constant amount of work and need a set difficulty to report their full speed without flooding the pool with shares. Each pool's connect page marks which fixed ports are suitable for rented hashrate.

How do I set a custom difficulty without changing ports?

Put it in the password field as d=NNNN, for example d=1000000. mkpool reads that and pins your share difficulty to that value on whichever port you connected to. It is the only thing the password is used for.

Do encrypted ports have different difficulty options?

No. TLS and Stratum V2 ports are offered in the same vardiff and fixed-difficulty flavours as the plain ports. Choosing encryption and choosing a difficulty tier are independent decisions, pick the difficulty that suits your hardware, then pick the plain, TLS or V2 port at that difficulty.

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