Software · head to head
Fluent Bit vs Fluentd
The short version
- Each has a real cost: Fluent Bit fluent Bit ships over 100 built in plugins against more than 1,000 external plugins available for Fluentd, so fewer integrations exist out of the box; Fluentd fluentd needs more than 60 MB of memory at runtime, against roughly 450 KB for Fluent Bit
- They diverge on capability: Fluent Bit covers Lightweight processing, Fluentd covers Filtering and buffering.
Where they differ
Only the attributes on which Fluent Bit and Fluentd actually diverge.
| Attribute | Fluent Bit | Fluentd |
|---|---|---|
| Founded | 2015 | 2011 |
Identical on both: starting price (Free), pricing model (open-source), free tier (Yes), platforms (Web, Api), user rating (Not yet rated), category (Unknown).
What each one covers
Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.
Only in Fluent Bit
- Lightweight processing
- Event filtering
Only in Fluentd
- Filtering and buffering
- Event routing
Both cover
- Log collection
- Data parsing
- API
- Webhooks
- REST
- Web support
- Api support
What people use each for
The jobs each tool is most often brought in to do.
Fluent Bit
- Lightweight log and metric forwarding from containers and edge devicesnot Fluentd
- Kubernetes node level log collection with a small memory footprintnot Fluentd
- Filtering and enriching telemetry before shipping it to a backendnot Fluentd
Fluentd
- Unified log collection and routing from many sources to many destinationsnot Fluent Bit
- Parsing and transforming log records before forwardingnot Fluent Bit
- Aggregating logs from containers into Elasticsearch, S3 or a SIEMnot Fluent Bit
Where each one falls short
Documented limitations, not opinions. Every one is a constraint you would hit in normal use.
Fluent Bit
- Fluent Bit ships over 100 built in plugins against more than 1,000 external plugins available for Fluentd, so fewer integrations exist out of the box
- It is written in C, so extending it beyond the built in plugins means writing C rather than Ruby
- Dependencies are zero only until a plugin requires one
Fluentd
- Fluentd needs more than 60 MB of memory at runtime, against roughly 450 KB for Fluent Bit
- Fluentd is built as a Ruby gem and depends on other gems, so a Ruby runtime is required
- Its capability comes from over 1,000 external plugins rather than built in functionality, so each added input or output is a separate dependency
- The Fluent Bit documentation states that cloud providers have switched from Fluentd to Fluent Bit for performance and compatibility and calls Fluent Bit the next generation solution
Pricing, plan by plan
Fluent Bit
Free- FreeFree
- Log collection
- Lightweight processing
- Data parsing
Fluentd
Free- FreeFree
- Log collection
- Data parsing
- Filtering and buffering
Which should you pick?
Choose Fluent Bit if
- You need lightweight processing.
- You want to start without paying.
- You work on Web, Api.
- You also want event filtering.
Choose Fluentd if
- You need filtering and buffering.
- You want to start without paying.
- You work on Web, Api.
- You also want event routing.
Questions people ask
- Is Fluent Bit or Fluentd better?
- Neither clearly leads. Fluent Bit starts at Free and Fluentd at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, Fluent Bit or Fluentd?
- Fluent Bit starts at Free and Fluentd at Free.
- Does Fluent Bit or Fluentd run on more platforms?
- Both run on Web, Api, so platform support will not decide this one for you.
- Can I use Fluent Bit for free?
- Both have a free tier, so you can try either at no cost before committing.
- What is Fluent Bit best used for?
- Fluent Bit is most often used for lightweight log and metric forwarding from containers and edge devices, kubernetes node level log collection with a small memory footprint, filtering and enriching telemetry before shipping it to a backend. Of those, lightweight log and metric forwarding from containers and edge devices and kubernetes node level log collection with a small memory footprint are not what Fluentd is typically brought in for.
- What can Fluent Bit do that Fluentd cannot?
- Fluent Bit covers Lightweight processing, Event filtering. Fluentd covers Filtering and buffering, Event routing. Both handle Log collection, Data parsing, API, Webhooks.