IIS Application Request Routing (ARR) review
A free, self-hosted IIS module for HTTP routing, balancing, monitoring, and caching.
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
IIS Application Request Routing (ARR) is a free, self-hosted IIS module that routes HTTP requests to content servers and distributes traffic across them. It is aimed at web server administrators and hosting providers already running Windows servers with IIS. The module can manage server farms in IIS Manager, making it relevant for teams that want request routing and balancing within an existing IIS environment rather than a separate hosted service.
ARR’s HTTP controls are its main strength. Rules can inspect URLs, headers, and server variables, while administrators can choose among multiple load-balancing algorithms. Health monitoring uses live traffic and URL tests; cookie-based client affinity can keep a client on a content server, and host-name affinity supports shared hosting. Reverse-proxy configurations and disk-based HTTP caching extend its role beyond distributing requests. These capabilities make ARR a fit for IIS-based HTTP workloads that benefit from centralized farm management and runtime statistics.
The deployment trade-off is a close tie to the IIS stack: ARR is installed on Windows servers running IIS and relies on the IIS URL Rewrite module for request inspection and routing rules. It is not a managed service, so the team operates the environment itself. Microsoft’s official page lists compatibility through IIS 10. For Windows/IIS users seeking free HTTP reverse proxying and balancing, ARR covers the core needs; teams wanting a managed option or balancing beyond its stated HTTP focus should consider alternatives.
IIS Application Request Routing (ARR) pros and cons
- Where it wins
- Routes HTTP requests using URLs, headers, and server variables
- Offers selectable balancing algorithms, health checks, and client affinity
- Includes reverse-proxy routing and disk-based HTTP caching
- Where it doesn't
- Requires Windows Server running IIS and the IIS URL Rewrite module
- Self-hosted only; it is not a managed service
- Focused on HTTP routing rather than broader load-balancing needs
IIS Application Request Routing (ARR) fact sheet, pricing and score →
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