log
The `log` crate is a lightweight logging facade for Rust that provides a unified API for libraries and applications. Instead of each library choosing its own logging backend, `log` abstracts the logging interface, letting end users select their preferred implementation (env_logger, fern, log4rs, etc.). It has been maintained since 2014 and is widely adopted in the Rust ecosystem.
Key facts
Objective fields from the source. Values we can't verify are shown as “Unknown” rather than guessed.
| Field | Value |
|---|---|
| Repository | rust-lang/log |
| Owner | rust-lang |
| Primary language | Rust |
| License | Apache-2.0 — OSI-approved |
| Stars | 2.5k |
| Forks | 287 |
| Open issues | 17 |
| Latest release | 0.4.33 (2026-06-20) |
| Last updated | 2026-06-24 |
| Source | https://github.com/rust-lang/log |
What log is
A zero-cost abstraction facade that decouples logging APIs from concrete implementations via compile-time trait-based dispatch. Provides macros (info!, warn!, error!, etc.) for structured and unstructured logging, with optional support for key-value structured logging via the `kv` feature. Minimal dependencies and designed for both library and application use.
Get the log source
Clone the repository and explore it locally.
git clone https://github.com/rust-lang/log.gitcd log# follow the project's README for install & configurationNeed it deployed, integrated, or customized instead? DEV.co ships production installs.
Best use cases
Implementation considerations
- Executables must initialize a concrete logger implementation (e.g., env_logger::init()) early in main(); log output before initialization is silently discarded.
- Libraries should depend only on `log`, never on a specific backend, to avoid forcing users' logging strategies.
- Minimum supported Rust version (MSRV) is defined in Cargo.toml and explicitly tested in CI; check compatibility before upgrading.
- Structured logging via `kv` feature requires serde or custom serialization; evaluate performance and dependency footprint for your use case.
- Logger implementations vary widely in configuration, output format, and performance; select based on application requirements (simplicity, configurability, async support, etc.).
When to avoid it — and what to weigh
- Single monolithic application with fixed logging needs — If you control the entire application stack and have no library dependencies, using a logging backend directly (env_logger, log4rs) may be simpler than adding a facade layer.
- Async/high-throughput logging performance critical — While `log` is lightweight, some implementations it delegates to may not support the throughput or latency guarantees required by very high-frequency logging scenarios; benchmark specific backends.
- Compile-time initialization requirements — The facade design assumes runtime initialization of a concrete logger; systems requiring static or const initialization may need custom approaches.
- No-std/embedded without backend support — The `log` crate itself can be no-std, but you still need a compatible backend implementation; not all standard backends support restricted environments.
License & commercial use
Licensed under Apache License 2.0 (Apache-2.0), a permissive OSI-approved license that permits commercial use, modification, and distribution with attribution and limited liability.
Apache-2.0 is a permissive license explicitly allowing commercial use. No additional licensing review or royalties required for proprietary applications. Redistribution or modification must include a copy of the license and statement of changes.
DEV.co evaluation signals
Editorial assessment — not user reviews. Directional, with an explicit confidence level.
| Signal | Assessment |
|---|---|
| Maintenance | Active |
| Documentation | Strong |
| License clarity | Clear |
| Deployment complexity | Low |
| DEV.co fit | Strong |
| Assessment confidence | High |
The `log` facade itself is minimal and does not process untrusted data; security depends on the chosen backend implementation. Ensure the selected logger does not inadvertently log sensitive data (passwords, tokens) and validates any configuration inputs. No known CVEs reported; long maintenance history suggests thorough community review.
Alternatives to consider
slog (Structured Logging)
More complex but powerful; provides built-in structured logging without a separate `kv` feature, and supports more advanced composable logger chains. Use if you need sophisticated filtering, async sinks, or advanced composition out of the box.
tracing
Modern alternative focused on async/span-based tracing and observability; integrates with Tokio and async Rust better than `log`. Use if your application is async-heavy and requires detailed span and event tracking.
Direct backend use (env_logger, log4rs, fern)
Skip the facade entirely if you control the entire codebase and have no library dependencies. Simpler dependency tree but loses the flexibility to swap backends later.
Build on log with DEV.co software developers
The `log` crate is a battle-tested foundation for logging. Contact Devco to assess backend implementations (env_logger, log4rs, fern) and design a logging strategy that scales with your application.
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log FAQ
Does `log` produce any output by itself?
Can I use `log` in a library?
What is the MSRV (minimum supported Rust version)?
Does `log` support structured logging?
Work with a software development agency
DEV.co is a software development agency delivering custom software development services to companies building on open source. Our software developers and web developers design, integrate, and ship production systems — spanning web development, APIs, AI, data, and cloud. If log is part of your open-source observability roadmap, our team can implement, customize, migrate, and maintain it.
Ready to integrate structured logging into your Rust project?
The `log` crate is a battle-tested foundation for logging. Contact Devco to assess backend implementations (env_logger, log4rs, fern) and design a logging strategy that scales with your application.