Softwr

Logging · head to head

Fluent Bit vs Fluentd

Fluent Bit logo

Fluent Bit

Logging

Fast and Lightweight Log Processor

From
Free
Rated
-
Full reviewWebsite
Fluentd logo

Fluentd

Logging

Open Source Data Collector for Unified Logging

From
Free
Rated
-
Full reviewWebsite

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.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which Fluent Bit and Fluentd actually diverge.

Attributes where Fluent Bit and Fluentd differ
AttributeFluent BitFluentd
Founded20152011

Identical on both: starting price (Free), pricing model (open-source), free tier (Yes), platforms (Web, Api), user rating (Not yet rated), category (Logging).

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.
Fluent Bit review

Choose Fluentd if

  • You need filtering and buffering.
  • You want to start without paying.
  • You work on Web, Api.
  • You also want event routing.
Fluentd review

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.

Answered from the vendors’ own pages

Fluent Bit: Is Fluent Bit free?

Yes, Fluent Bit is a CNCF graduated open-source project with no vendor lock-in and is freely available for download and use.

Source
Fluentd: How much does Fluentd cost?

Fluentd is free and open-source under the Apache 2 License from the Cloud Native Computing Foundation (CNCF). There are no subscription fees, licensing costs, or commercial pricing tiers.

Source
Fluent Bit: Does Fluent Bit offer an Enterprise option?

The website navigation mentions an Enterprise section suggesting paid offerings exist, but specific pricing and details are not provided on the publicly available pages.

Source
Share

Related pages

More on Fluent Bit

More on Fluentd

Keep looking

Other head to heads