swift-log
swift-log is Apple's official logging API for Swift, providing a unified interface for application and library logging across the Swift ecosystem. It is API-only—actual log output requires a separate backend implementation chosen by the developer.
Key facts
Objective fields from the source. Values we can't verify are shown as “Unknown” rather than guessed.
| Field | Value |
|---|---|
| Repository | apple/swift-log |
| Owner | apple |
| Primary language | Swift |
| License | Apache-2.0 — OSI-approved |
| Stars | 4k |
| Forks | 343 |
| Open issues | 21 |
| Latest release | 1.14.0 (2026-06-24) |
| Last updated | 2026-06-30 |
| Source | https://github.com/apple/swift-log |
What swift-log is
swift-log defines a protocol-based logging abstraction with metadata support, structured logging, and pluggable handlers. It does not perform I/O itself; instead, it coordinates log routing through community-maintained backends that handle formatting, storage, and transport.
Get the swift-log source
Clone the repository and explore it locally.
git clone https://github.com/apple/swift-log.gitcd swift-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
- Requires explicit backend selection and integration; cannot log without a handler implementation. Common choices: apple/swift-log-oslog (Darwin), swift-log-syslog (syslog), or third-party backends.
- Metadata is optional but recommended for production; design logging keys early to avoid inconsistent context propagation across services.
- Log level filtering is configurable per logger instance; plan log-level strategy at initialization to balance verbosity and performance.
- Thread-safe by design; safe for concurrent logging in multi-threaded applications, but backend performance depends on handler choice.
- Minimal dependencies; no required transitive dependencies, reducing supply-chain risk and integration friction.
When to avoid it — and what to weigh
- High-Performance, Latency-Sensitive Logging — If sub-microsecond logging latency is required, the abstraction layer overhead and choice of backend implementation may not meet extreme performance constraints. Benchmark with your target backend first.
- Unified Logging Without Backend Selection — swift-log requires active choice and maintenance of a compatible backend. If you need logging to work out-of-the-box, you must also select and integrate a backend (e.g., swift-log-oslog, swift-log-syslog).
- Proprietary or Closed-Source Logging Infrastructure — If your organization has legacy or proprietary logging systems, integrating swift-log may require writing a custom backend. Consider cost-benefit before committing.
- Non-Swift Languages or Mixed Language Projects — swift-log only works with Swift. If your project spans multiple languages, you may need separate logging strategies or a language-agnostic wrapper.
License & commercial use
Apache License 2.0 (Apache-2.0). Standard, OSI-approved permissive license allowing commercial use, modification, and distribution with attribution.
Apache-2.0 is a permissive, commercial-use-friendly license. Code may be used in commercial products without royalty or source disclosure, provided Apache-2.0 is attributed. Consult legal counsel for specific commercial scenarios or if combining with other licenses.
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 |
swift-log itself does not validate or sanitize log content; log injection attacks possible if user input is logged unsanitized. Backend handler choice (e.g., file permissions, transport encryption) determines actual security posture. No known CVEs in recent history. Security issues should be reported via Apple's process on the GitHub Security tab.
Alternatives to consider
os_log (Apple Foundation)
Native to Darwin (macOS, iOS); simpler for single-platform apps, but less flexible for server/multi-platform Swift. swift-log-oslog bridges both.
Serilog (C#) / Log4j (Java) equivalents
If migrating from non-Swift ecosystems, those ecosystems have richer built-in logging; swift-log is the Swift ecosystem standard but requires deliberate backend choice.
Custom logging via print() or third-party single-purpose libraries
Simpler for small scripts; lacks abstraction, metadata support, and unified control, leading to fragmentation in multi-library projects.
Build on swift-log with DEV.co software developers
swift-log is the de facto standard in the Swift ecosystem. Choose a backend, integrate, and start logging with structured metadata today.
Talk to DEV.coRelated open-source tools
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swift-log FAQ
Do I need a backend to use swift-log?
Is swift-log thread-safe?
Can I use swift-log in production?
How do I add context to logs (e.g., request IDs)?
Work with a software development agency
Need help beyond evaluating swift-log? DEV.co is a software development agency offering software development services and web development for teams of every size. Our software developers and web developers build custom software, web applications, APIs, and open-source observability integrations — and maintain them long-term.
Ready to standardize logging in your Swift project?
swift-log is the de facto standard in the Swift ecosystem. Choose a backend, integrate, and start logging with structured metadata today.