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Fortio

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description Fortio Overview

Fortio is an open-source website speed testing tool that analyzes a webpage’s performance by measuring various metrics like First Contentful Paint, Largest Contentful Paint, and total load time to identify optimization opportunities.

help Fortio FAQ

What is Fortio actually used for in practice?

Fortio is an open-source tool primarily used for load testing and latency measurement of web services, originally developed as part of the Istio service mesh project. It generates controlled HTTP and gRPC traffic while recording response-time percentiles, throughput, and error rates, rather than measuring browser-side rendering metrics.

How is Fortio related to Istio?

Fortio was originally created to benchmark and stress-test Istio service mesh performance, and it ships as a component within Istio installations. Users can deploy Fortio as a container inside a Kubernetes cluster to generate internal traffic and measure how Istio's sidecar proxies affect latency and throughput.

Is Fortio free and open-source?

Yes, Fortio is completely free and open-source, available on GitHub. It can be run as a standalone binary, inside a Docker container, or as a Kubernetes deployment, making it accessible for both individual developers and enterprise teams.

Can Fortio measure web vitals like Largest Contentful Paint?

No, Fortio focuses on backend and network-layer performance—latency, throughput, and error rates under load—rather than browser-rendered metrics like Largest Contentful Paint or First Contentful Paint. Tools such as Google Lighthouse or WebPageTest are better suited for measuring those front-end web vitals.

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