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Logging · head to head

Azure Monitor vs Fluentd

Azure Monitor logo

Azure Monitor

Logging

Azure's Monitoring and Diagnostics Service

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: Azure Monitor billed per GB ingested across three separate log plans, Auxiliary, Basic and Analytics, so the plan chosen changes the rate as much as the volume does; Fluentd fluentd needs more than 60 MB of memory at runtime, against roughly 450 KB for Fluent Bit
  • They diverge on capability: Azure Monitor covers Metrics collection, Fluentd covers Data parsing.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which Azure Monitor and Fluentd actually diverge.

Attributes where Azure Monitor and Fluentd differ
AttributeAzure MonitorFluentd
Pricing modelusage-basedopen-source
Founded20102011

Identical on both: starting price (Free), 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 Azure Monitor

  • Metrics collection
  • Alerts and notifications
  • Custom dashboards

Only in Fluentd

  • Data parsing
  • Filtering and buffering
  • Event routing

Both cover

  • Log collection
  • API
  • Webhooks
  • REST
  • Web support
  • Api support

What people use each for

The jobs each tool is most often brought in to do.

Azure Monitor

  • Collecting logs and metrics from Azure resourcesnot Fluentd
  • Alerting on metric thresholds and log queriesnot Fluentd
  • Application performance monitoring through Application Insightsnot Fluentd
  • Long-term log retention for compliancenot Fluentd
  • Querying operational data with KQLnot Fluentd

Fluentd

  • Unified log collection and routing from many sources to many destinationsnot Azure Monitor
  • Parsing and transforming log records before forwardingnot Azure Monitor
  • Aggregating logs from containers into Elasticsearch, S3 or a SIEMnot Azure Monitor

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Azure Monitor

  • Billed per GB ingested across three separate log plans, Auxiliary, Basic and Analytics, so the plan chosen changes the rate as much as the volume does
  • Only the first 5 GB a month of Analytics logs is free per billing account
  • Retention beyond the base period is charged per GB per month, up to 2 years interactive and 12 years long term
  • Log queries and search jobs are billed per GB scanned, so investigating an incident costs money
  • Alert rules are billed per time series for metrics and by execution frequency for logs
  • The pricing page shows placeholders rather than rates until a region and currency are chosen

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

Azure Monitor

Free
  • FreeFree
    • Log collection
    • Metrics collection
    • Alerts and notifications

Fluentd

Free
  • FreeFree
    • Log collection
    • Data parsing
    • Filtering and buffering

Which should you pick?

Choose Azure Monitor if

  • You need metrics collection.
  • You want to start without paying.
  • You work on Web, Api.
  • You also want alerts and notifications.
Azure Monitor review

Choose Fluentd if

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

Questions people ask

Is Azure Monitor or Fluentd better?
Neither clearly leads. Azure Monitor 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, Azure Monitor or Fluentd?
Azure Monitor starts at Free and Fluentd at Free.
Does Azure Monitor or Fluentd run on more platforms?
Both run on Web, Api, so platform support will not decide this one for you.
Can I use Azure Monitor for free?
Both have a free tier, so you can try either at no cost before committing.
What is Azure Monitor best used for?
Azure Monitor is most often used for collecting logs and metrics from azure resources, alerting on metric thresholds and log queries, application performance monitoring through application insights, long-term log retention for compliance. Of those, collecting logs and metrics from azure resources and alerting on metric thresholds and log queries are not what Fluentd is typically brought in for.
What can Azure Monitor do that Fluentd cannot?
Azure Monitor covers Metrics collection, Alerts and notifications, Custom dashboards. Fluentd covers Data parsing, Filtering and buffering, Event routing. Both handle Log collection, API, Webhooks, REST.

Answered from the vendors’ own pages

Azure Monitor: How does Azure Monitor billing work?

Billing is based on data volume ingested into Azure Monitor. Additional charges apply separately for alerts, notifications, web tests, and data export. Activity log and platform metrics are automatically collected with an Azure subscription.

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
Azure Monitor: What savings are available with Azure Monitor?

Capacity reservations offer up to 36% savings compared to standard pay-as-you-go pricing when you commit to reserved capacity upfront.

Source
Azure Monitor: Is there a free tier for Azure Monitor?

No dedicated free tier exists. Activity log and platform metrics are automatically collected with an Azure subscription, but detailed monitoring requires additional configuration and associated costs.

Source
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