head to head · open source
Apache SkyWalking vs defmt
Apache SkyWalking has 24,988 GitHub stars, 6,632 forks, 41 open issues and last shipped 2 days ago. defmt has 1,241 stars, 135 forks, 117 open issues and last shipped 3 days ago. Apache SkyWalking leads on adoption by 1,914% (24,988 vs 1,241 stars). Apache SkyWalking is written in Java under Apache-2.0; defmt is written in Rust under Apache-2.0. Apache SkyWalking has attracted 27% as many forks as stars, defmt 11%. Apache SkyWalking 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
| Apache SkyWalking | defmt | |
|---|---|---|
| GitHub stars | ★ 25K | ★ 1.2K |
| License | Apache-2.0 | Apache-2.0 |
| Written in | Java | Rust |
| Last push | 2026-11-03 | 2026-11-02 |
| Forks | ⑂ 6.6K | ⑂ 135 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Apache SkyWalking if
- You weight community size — 25K stars and counting
- You want the Apache-2.0 license terms
- Your stack matches Java
- 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 Apache SkyWalking
Apache SkyWalking ========== SkyWalking : an APM (Application Performance Monitoring) system, especially designed for microservices, cloud native and container based architectures. Abstract SkyWalking is an open source APM system that provides monitoring, tracing and diagnosing capabilities for distributed systems in Cloud Native architectures. Distributed Tracing End to end distributed tracing. Service topology analysis, service centric observability and APIs dashboards. Agents for your stack Java, .Net Core, PHP, NodeJS, Golang, LUA, Rust, C++, Client JavaScript and Python agents with active development and…
read the full Apache SkyWalking 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 Apache SkyWalking or defmt more popular?
Apache SkyWalking has 24,988 GitHub stars and defmt has 1,241. Apache SkyWalking has the larger community by that measure.
Are Apache SkyWalking and defmt free?
Both are open source. Apache SkyWalking is licensed under Apache-2.0 and defmt under Apache-2.0. Neither carries a licence fee.
What is the difference between Apache SkyWalking and defmt?
Apache SkyWalking is written in Java 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, Apache SkyWalking or defmt?
Choose Apache SkyWalking if you want the larger community (24,988 stars) or its Apache-2.0 licence terms. Choose defmt if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.