Software · head to head
Fluentd vs Fluent Bit
The short version
- Each has a real cost: Fluentd fluentd needs more than 60 MB of memory at runtime, against roughly 450 KB for Fluent Bit; 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
- They diverge on capability: Fluentd covers Filtering and buffering, Fluent Bit covers Lightweight processing.
Where they differ
Only the attributes on which Fluentd and Fluent Bit actually diverge.
| Attribute | Fluentd | Fluent Bit |
|---|---|---|
| Founded | 2011 | 2015 |
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 Fluentd
- Filtering and buffering
- Event routing
Only in Fluent Bit
- Lightweight processing
- Event filtering
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.
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
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
Where each one falls short
Documented limitations, not opinions. Every one is a constraint you would hit in normal use.
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
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
Pricing, plan by plan
Fluentd
Free- FreeFree
- Log collection
- Data parsing
- Filtering and buffering
Fluent Bit
Free- FreeFree
- Log collection
- Lightweight processing
- Data parsing
Which should you pick?
Choose Fluentd if
- You need filtering and buffering.
- You want to start without paying.
- You work on Web, Api.
- You also want event routing.
Choose Fluent Bit if
- You need lightweight processing.
- You want to start without paying.
- You work on Web, Api.
- You also want event filtering.
Questions people ask
- Is Fluentd or Fluent Bit better?
- Neither clearly leads. Fluentd starts at Free and Fluent Bit at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, Fluentd or Fluent Bit?
- Fluentd starts at Free and Fluent Bit at Free.
- Does Fluentd or Fluent Bit run on more platforms?
- Both run on Web, Api, so platform support will not decide this one for you.
- Can I use Fluentd for free?
- Both have a free tier, so you can try either at no cost before committing.
- What is Fluentd best used for?
- Fluentd is most often used for unified log collection and routing from many sources to many destinations, parsing and transforming log records before forwarding, aggregating logs from containers into elasticsearch, s3 or a siem. Of those, unified log collection and routing from many sources to many destinations and parsing and transforming log records before forwarding are not what Fluent Bit is typically brought in for.
- What can Fluentd do that Fluent Bit cannot?
- Fluentd covers Filtering and buffering, Event routing. Fluent Bit covers Lightweight processing, Event filtering. Both handle Log collection, Data parsing, API, Webhooks.