Fluent Bit vs Fluentd
A side-by-side comparison of two self-hosted monitoring & status options — licensing, setup difficulty, resource needs, and what each one replaces.
| Feature | Fluent Bit | Fluentd |
|---|---|---|
| Deploy effort | Under-an-hour setup | Under-an-hour setup |
| Health score | 92 · Excellent | 94 · Excellent |
| Category | Monitoring & Status | Monitoring & Status |
| License | Apache-2.0 | Apache-2.0 |
| Language | C | Ruby |
| Setup difficulty | Medium | Medium |
| Min. RAM | 32 MB | 128 MB |
| Deployment | docker, kubernetes, binary | docker, kubernetes, binary |
| GitHub stars | ★ 8,121 | ★ 13,590 |
| First released | 2015 | 2011 |
| Replaces | Logstash | Logstash |
What are Fluent Bit and Fluentd?
Fluent Bit
Fluent Bit is a fast, lightweight telemetry agent for collecting and processing logs, metrics, and traces. Written in C, it is designed for edge and container environments with minimal resource use.
- Very small memory footprint
- Logs, metrics, and traces
- Kubernetes-native filters
- High throughput in C
Fluentd
Fluentd is an open-source data collector that unifies log collection and consumption across many sources and destinations. Its plugin ecosystem makes it a flexible logging layer for any infrastructure.
- Unified logging layer
- Over 1000 plugins
- Reliable buffering
- CNCF graduated project
Fluent Bit vs Fluentd: key differences
Fluent Bit is written in C, while Fluentd is built with Ruby. Fluent Bit is the lighter option, starting around 32 MB of RAM against 128 MB for Fluentd. Fluentd is the more established project (first released 2011), while Fluent Bit arrived in 2015.
Why pick each one
Choose Fluent Bit if…
- Ideal for containers and edge
- Extremely efficient
Watch out for
- Fewer plugins than Fluentd
- Config syntax is terse
Choose Fluentd if…
- Huge plugin ecosystem
- Proven at scale
Watch out for
- Heavier than Fluent Bit
- Ruby runtime overhead
Frequently asked questions
Is Fluent Bit or Fluentd better?
Neither is universally better. Fluentd has the larger community; both share a medium setup difficulty, so the decision comes down to features and licensing.
Are Fluent Bit and Fluentd free and open-source?
Yes. Fluent Bit is licensed under Apache-2.0 and Fluentd under Apache-2.0. Both can be self-hosted at no software cost.
Can I run Fluent Bit and Fluentd with Docker?
Fluent Bit: yes. Fluentd: yes.
Which is lighter on resources, Fluent Bit or Fluentd?
Fluent Bit has the smaller minimum footprint at 32 MB of RAM, compared to about 128 MB for Fluentd. Real-world usage depends on library size, user count, and enabled features.