Fluentd to Fluent Bit: A Migration Guide

When and why to migrate? Why Migrate? Fluentd vs. Fluent Bit: What are the Differences Background Performance Routing Telemetry signal focus Custom processing Custom plugins Monitoring How to get started with a Fluentd to Fluent Bit migration Deployment Deployed as an Aggregator / Collector Adding a Telemetry Pipeline Configuration Custom Plugins Custom Processing Logic Migrating Portions at a Time Conclusion Frequently Asked Questions Why migrate from Fluentd to Fluent Bit What are some differences between Fluentd and Fluent Bit? Can Fluentd and Fluent Bit work together? Posted on October 1, 2025 by Anurag Gupta | Fluent Bit Maintainer | Field Architect | Chronosphere CNCF projects highlighted in this post Fluentd was created over 14 years ago and still continues to be one of the most widely deployed technologies for log collection in the enterprise. Fluentd’s distributed plugin architecture and highly permissive licensing made it ideal as part of the Cloud Native Computing Foundation (CNCF) as a now graduated project. However, enterprises drowning in telemetry data are now requiring solutions that have higher performance, more native support for evolving schemas and formats, and increased flexibility in processing. Enter Fluent Bit. Fluent Bit , while initially growing as a sub-project within the Fluent ecosystem , expanded from Fluentd to support all telemetry types – logs, metrics, and traces. Fluent Bit now is the more popular of the two with over 15 billion deployments and used by Amazon, Google, Oracle and Microsoft to name a few. Fluent Bit also is fully aligned with OpenTelemetry signals, format and protocol, which ensures that users will be able to continue handling telemetry data as it grows and evolves. Among the most frequent questions we get as the maintainers of the projects are: How do we migrate? What should we watch out for? And what business value do we get for migrating? This article aims to answer these questions with examples. We want to help make it an easy decision to migrate from Fluentd to Fluent Bit. Here is a quick list of the reasons users switch from Fluentd to Fluent Bit: Higher performance for the same resources you are already using Full OpenTelemetry support for logs, metrics, and traces as well as Prometheus support for metrics Simpler configuration and routing ability to multiple locations Higher velocity for adding custom processing rules Integrated monitoring to better understand performance and dataflows To understand all the differences between the projects, it is important to understand the background of each project and the era it was built for. With Fluentd, the main language is Ruby and initially designed to help users push data to big data platforms such as Hadoop.