Karlsen is a free, open source blockchain node and mining toolkit for people who want to run their own software on Windows. It is a fork of Kaspa, and its developers built it around GPU mining with the goal of giving smaller miners a realistic chance against large ASIC farms. If you are a hobbyist with a graphics card, a node operator, or a developer who wants to study a Kaspa-derived network, this is the kind of program that fits.
Karlsen for Windows is released under the ISC license, and the latest version is v2.3.0, with the most recent code update dated February 12, 2026. That makes the project actively maintained as of this writing. Expect a first run that generates a large DAG file, and read the setup notes before you start a long mining session.
What Is Karlsen and Why Was It Forked from Kaspa?
A fork is a copy of an existing codebase that its maintainers modify to create a separate network with different rules. Karlsen starts from Kaspa and changes the mining design, so the two projects share foundations but do not behave identically.
The central idea is to make mining less dependent on ASIC hardware. ASICs are chips built for a single mining algorithm, and when a few large operations own many of them, mining power concentrates in a small number of hands. The developers focus on GPU mining instead, so owners of ordinary graphics cards can still contribute. They describe the goal as more decentralization and more room for small-scale miners.
The team also talks about connecting blockchain technology with decentralized finance and with traditional payment systems. In practice, that means the software is meant to serve as a foundation for applications beyond simple mining, though most day-to-day users will first encounter it as a node and miner. Read the documentation to see which parts are ready for your use case.
Who Karlsen Is For
Karlsen suits a few distinct groups. The first is hobbyist miners with a gaming PC. A graphics card that sits idle overnight can run the GPU miner, and the project's design is aimed at exactly that kind of hardware rather than industrial rigs.
The second group is node operators who want their own copy of the network software rather than relying on someone else's server. Running a node means your software checks the chain's rules directly, which is useful if you care about verifying data yourself.
The third group is developers. The codebase is written in Go and published under the ISC license, so programmers can read how a Kaspa-derived node handles blocks and mining. A student comparing consensus designs could use the repository as a case study. Beginners who have never used a command line should expect a learning curve, and it is wise to practice with the CPU miner before investing time in GPU settings.
How Proof of Work Mining and the DAG Fit Together
Proof of work mining means computers compete to solve a hard puzzle, and the first to solve it can add a block. The rate at which a device attempts these calculations is called its hashrate. Higher hashrate generally means more attempts per second, but the outcome also depends on competition across the whole network.
Karlsen's miners use a DAG, a large dataset that the algorithm reads repeatedly while hashing. The KarlsenHashv2 miner uses a 4GB DAG. Because the file is needed during mining, its size matters for graphics cards with limited video memory. The first run generates it, which takes significant time and processor effort.
The project documents three mining algorithms: kHeavyHash, Blake3 and KarlsenHash. Different algorithms reward different hardware, so a configuration built for one may not suit another. Compare the documentation before choosing a setup, and test with a short session to measure your own output rather than relying on estimates.
Key features
Built-in CPU miner
Karlsen GPU miner
Team Red Miner support
Supported coins
Karlsen's documentation names Kaspa (KAS) and Cosmos (ATOM) as the networks and coins it references. The mining work is organized around three algorithms: kHeavyHash, Blake3 and KarlsenHash. Confirm in the documentation which algorithm each miner uses before you configure it.
How to install Karlsen on Windows
- 1
Get the latest release
Open the official project page or the Karlsen releases on GitHub and select the newest version, v2.3.0 at the time of writing. Download only from the official website or the project's GitHub Releases page, and avoid copies shared in forums or chat messages.
- 2
Verify the file
Compute the SHA-256 checksum of the downloaded file with PowerShell using Get-FileHash, then compare the result with the value published alongside the release. If the values do not match, delete the file and download it again from the official source. If a signature is published, check it as well.
- 3
Install or unpack the build
Run the Windows installer, or extract the Windows build to a folder you control. Choose a location in your user directory rather than a system folder, so updates and logs are easy to manage.
- 4
Start the node and let it prepare
Launch karlsend and allow the first run to finish. It generates a 4GB DAG file using 8 CPU threads, so expect a heavy processor load and make sure the drive has room for the file.
-
Add the miner after the node runs
Set up the CPU or GPU miner once the node is running. Read the documentation for the command-line options that match your hardware, and start with a short test session.
System requirements
- Windows, with a build or installer available from the project
- At least 4GB of free disk space for the DAG file used by the KarlsenHashv2 miner
- A processor able to run 8 threads during the first run, which generates the DAG
- A dedicated graphics card only if you plan to use the GPU miner; the built-in CPU miner does not need one
How to use Karlsen
Once the files are in place, the workflow is straightforward, though the first run takes patience. Work through these steps in order and watch the output for errors.
- Start the karlsend node and let it finish its first run, which generates the DAG file.
- Allow the node to sync with the network before you judge its performance.
- Confirm the node is reachable and that the log is not filling with repeated errors.
- Test the built-in CPU miner for a short period to confirm that mining starts and runs.
- Read the documentation for GPU miner settings, then launch the Karlsen GPU miner with the options you chose.
- Monitor hashrate and temperature, and stop the miner if the system overheats.
- Check the GitHub Releases page from time to time so you know when a newer version is available.
Pros & cons
- Free to use and released under the ISC license
- Source code is public on GitHub for review and study
- Includes CPU and GPU mining options within one project
- Recent code update dated February 12, 2026
- Supports Windows, macOS and Linux
- Mining requires a 4GB DAG file and a heavy first-run processor load
- Antivirus tools may flag mining software as suspicious
- Setup relies on command-line steps and reading the documentation
- Best suited to users comfortable with technical tools
Is Karlsen safe?
Download only from the official website or the project's GitHub Releases page, and never accept a copy from a forum post or a chat message. Before running the file, compute its SHA-256 checksum and compare it with the published value, and check a signature if one is provided. Mining software is a common target for malware, and many antivirus tools flag it even when it is legitimate. If that happens, verify the file first and add a narrow exception rather than turning protection off entirely. Never enter a seed phrase on third-party websites or into software you have not verified. The project shows recent activity, but check the latest version on the official website before you install.
- Official source only. Download from github.com/karlsen-network/karlsend. Ignore ads and lookalike domains.
- Check the SHA-256. Compare the installer hash with the value the developer publishes before running it.
- Never share your seed phrase. No developer, support agent or website — including CryptApps — will ever ask for it.
Alternatives
Karlsen sits in a crowded corner of the market: software that runs nodes for proof of work and related networks. Rusty Kaspa is the full node and command-line wallet for Kaspa itself, so it is the closer choice if you want the original network without a fork. Spectre runs its own node software for a separate network, and Cosmos Hub's gaiad is a node for a proof of stake ecosystem, which works differently from mining. Bitcoin Core is the reference client for Bitcoin. Karlsen stands out for its GPU-centric mining goals and for bundling CPU and GPU miners in one project. Choose based on which network you want to support and what hardware you own.
Specifications
- Price
- Free
- Type
- Open source
- License
- ISC
- Latest version
- v2.3.0
- Last update
- 12 Feb 2026
- Windows support
- Yes (Windows build or installer)
- Source code
- github.com/karlsen-network/karlsend
Frequently asked questions
Yes. Karlsen is free and open source, released under the ISC license, which allows you to use, study and modify the code. The project lists Windows among its supported platforms through a Windows build or installer, along with macOS and Linux. Because there is no purchase step, your main focus should be verifying the file you download and reading the setup notes before you run it.
Karlsen's code is public for review, but safety depends on where you get the files and how you handle them. Obtain them only through the project's official channels, check the SHA-256 checksum, and keep your antivirus active. Mining software often triggers warnings, so verify the file before making any exception. Never share a seed phrase with anyone or enter it on a third-party site.
Yes. The karlsend node includes a built-in CPU miner, so you can test mining without a graphics card. CPU mining is mainly useful for learning how the software behaves and confirming that your setup works. Results on a processor are usually far lower than on a dedicated GPU, so treat CPU mining as a trial rather than a primary plan. Check the documentation for the current options.
Karlsen is a fork of Kaspa, meaning it starts from Kaspa's code and changes parts of the network. Its main difference is a GPU-centric approach to mining, designed to limit the advantage of ASIC farms and make mining more accessible to individuals. Kaspa remains the original network. If you want the upstream project, look at Rusty Kaspa, while Karlsen is the choice for its GPU mining goals.
Yes. The project lists Windows, macOS and Linux as supported platforms. This page focuses on the Windows build or installer, but the other systems are covered too. Installation details may differ by operating system, so follow the documentation for your platform and choose the release that matches your machine.
Check the GitHub Releases page or the official website for newer versions, such as the latest v2.3.0 release. Download the new file, verify its SHA-256 checksum against the published value, and stop the node before replacing files. Keep a copy of your old folder until the new version runs correctly. Updating in this order reduces the risk of a broken install.
Yes. The latest version is v2.3.0, and the most recent code update is dated February 12, 2026. That recent activity suggests the project is currently maintained, but maintenance status can change over time. Look at the repository's commit history and release notes before you depend on the software for important work.
No. You can run the node and the built-in CPU miner without a graphics card. A dedicated GPU is only necessary if you want to use the GPU miner. Keep in mind that the GPU miner relies on a 4GB DAG file, so make sure your system has room for it and that your video memory can handle the workload.
Verdict
Karlsen for Windows suits users who want a free, open source node and miner built around the idea of GPU mining. It is most useful for hobbyists with graphics cards, node operators who want their own copy of Kaspa-derived software, and developers who want to study the Go code. It is less suitable for people who expect quick results without reading documentation or who lack disk space for the 4GB DAG. Start with the node and CPU miner, verify your download, and move to the GPU miner once you understand the setup.