head to head · open source
Grafana Loki vs defmt
Grafana Loki has 29,120 GitHub stars, 4,173 forks, 1,620 open issues and last shipped yesterday. defmt has 1,241 stars, 135 forks, 117 open issues and last shipped 3 days ago. Grafana Loki leads on adoption by 2,246% (29,120 vs 1,241 stars). Grafana Loki is written in Go under AGPL-3.0; defmt is written in Rust under Apache-2.0. Grafana Loki has attracted 14% as many forks as stars, defmt 11%. Grafana Loki was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (logging), so they are genuine substitutes rather than adjacent tools.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
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Side by side
| Grafana Loki | defmt | |
|---|---|---|
| GitHub stars | ★ 29K | ★ 1.2K |
| License | AGPL-3.0 | Apache-2.0 |
| Written in | Go | Rust |
| Last push | 2026-11-04 | 2026-11-02 |
| Forks | ⑂ 4.2K | ⑂ 135 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Grafana Loki if
- You weight community size — 29K stars and counting
- You want the AGPL-3.0 license terms
- Your stack matches Go
- You value the larger contributor base for long-term maintenance
pick defmt if
- You want the defmt feature set and don't need the biggest community
- You prefer the Apache-2.0 license terms
- Your stack matches Rust
- You evaluated both and defmt fits your workflow better
About Grafana Loki
Loki: like Prometheus, but for logs. Loki is a horizontally scalable, highly available, multi tenant log aggregation system inspired by Prometheus. It is designed to be very cost effective and easy to operate. It does not index the contents of the logs, but rather a set of labels for each log stream. Compared to other log aggregation systems, Loki: does not do full text indexing on logs. By storing compressed, unstructured logs and only indexing metadata, Loki is simpler to operate and cheaper to run. indexes and groups log streams using the same labels you’re already using with Prometheus, enabling you to…
read the full Grafana Loki overview →
About defmt
defmt defmt ("de format", short for "deferred formatting") is a highly efficient logging framework that targets resource constrained devices, like microcontrollers. For more details about the framework check the book at . Components This repository contains the following packages: MSRV The minimum supported Rust version is 1.76 (or Ferrocene 24.05) for the crates that cross compile to your microcontroller. The minimum supported Rust version is 1.83 for all host side crates. The defmt crates are tested against the latest stable Rust version and the MSRV. Developer Information Running Tests Tests are run using…
read the full defmt overview →
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Frequently asked questions
Is Grafana Loki or defmt more popular?
Grafana Loki has 29,120 GitHub stars and defmt has 1,241. Grafana Loki has the larger community by that measure.
Are Grafana Loki and defmt free?
Both are open source. Grafana Loki is licensed under AGPL-3.0 and defmt under Apache-2.0. Neither carries a licence fee.
What is the difference between Grafana Loki and defmt?
Grafana Loki is written in Go and defmt in Rust. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, Grafana Loki or defmt?
Choose Grafana Loki if you want the larger community (29,120 stars) or its AGPL-3.0 licence terms. Choose defmt if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.