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SPECIFICTION
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Harmonia

github.com

Free plan LinuxSelf-hosted
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Spec score 8.0 #28 of 64 in Artifact repository software

What it is

Harmonia is free, open-source software for serving a Nix store as a binary cache over HTTP. Written in Rust for Linux self-hosting, it supports HTTP range requests for NAR streaming and streaming build logs. The /serve// endpoint can provide package contents and discover index.html to serve websites directly from the Nix store. Harmonia can transparently compress content with zstd and provide TLS when no frontend web server is used. Documentation covers a NixOS module and nginx HTTPS frontend configuration for a public cache. Narinfo signing is disabled unless private signing-key paths are supplied. Prometheus metrics are available at /metrics, with a Grafana dashboard included in the repository. Since version 3.1.0, metadata is read directly from db.sqlite without a nix-daemon connection. Version 3.3.0 adds harmonia-gc for removing store garbage while nix-daemon builds. It uses the MIT License.

Spec sheet

What it does
Harmonia is a Nix binary cache that serves the /nix/store over HTTP and is written in Rust.Read 4 Oct 2026 · github.com
Purpose
Harmonia serves a Nix store as a binary cache over HTTP and is written in Rust.Read 9 Oct 2026 · github.com
Support
The repository points users to its contributing guide and architecture documentation for project participation and technical details.Read 9 Oct 2026 · github.com
License
The project is licensed under the MIT License.Read 4 Oct 2026 · github.com
Build logs
It supports streaming build logs.Read 9 Oct 2026 · github.com
Cache signing
Narinfo signing can be enabled by providing paths to private signing keys; signing is disabled by default when no secret key is configured.Read 9 Oct 2026 · github.com
Compression
It can transparently compress content with zstd.Read 9 Oct 2026 · github.com
Maintainer
The repository identifies Mic92 as a maintainer.Read 9 Oct 2026 · github.com
Metadata access
Since version 3.1.0, harmonia-cache reads store metadata directly from db.sqlite without connecting to nix-daemon.Read 4 Oct 2026 · github.com
Monitoring
Harmonia exposes Prometheus metrics at `/metrics` and provides a Grafana dashboard in the repository.Read 9 Oct 2026 · github.com
NAR streaming
It supports HTTP range requests for streaming NAR files.Read 9 Oct 2026 · github.com
Nix garbage collection
The 3.3.0 release adds harmonia-gc, which removes garbage from the Nix store and can run while nix-daemon is building.Read 4 Oct 2026 · github.com
NixOS
The README documents configuring Harmonia as a public binary cache with a NixOS module and nginx as an HTTPS frontend.Read 4 Oct 2026 · github.com
NixOS integration
The project documents a NixOS module and example configurations using nginx as a frontend.Read 9 Oct 2026 · github.com
Package serving
Its `/serve/<narhash>/` endpoint serves package contents and can discover index.html files to serve websites from the Nix store.Read 9 Oct 2026 · github.com
Recent release
The latest listed release is harmonia-v3.3.0.Read 9 Oct 2026 · github.com
Signing
Harmonia does not sign narinfo by default without a secret key; signing can be enabled by providing private key paths.Read 4 Oct 2026 · github.com
Storage metadata
The cache reads store metadata directly from the Nix SQLite database and does not require a nix-daemon connection.Read 9 Oct 2026 · github.com
TLS
Harmonia can provide TLS directly when no frontend web server is used.Read 9 Oct 2026 · github.com

Plans and prices

Harmonia Free Open-source Nix binary cache software · self-hosted Read 9 Oct 2026 · github.com

Every Harmonia plan and price →

Strong points and limits

Strong points

  • Free MIT-licensed open-source software
  • NAR range streaming and build-log streaming
  • zstd compression and optional built-in TLS
  • Prometheus metrics and Grafana dashboard
  • NixOS module and nginx documentation

Limits

  • Linux and self-hosted deployment only
  • Narinfo signing is off by default
  • No free trial is offered

Who it suits

Harmonia suits Linux users who want to self-host a Nix binary cache and configure its storage, TLS, signing, and monitoring.

Verdict

Harmonia provides a focused HTTP cache for Nix stores with operational tooling and NixOS guidance. Administrators must configure signing when needed and run the service themselves.

Where Specifiction places it

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