FlowViewer review
A focused, free flow-analysis suite for teams managing their own collection infrastructure.
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
FlowViewer is an open-source network traffic analysis toolset for organizations that export NetFlow or related flow data from network devices. Its browser-based suite includes FlowViewer for text-based reports and filtering, FlowGrapher for traffic graphs, and FlowMonitor for long-term traffic monitoring. It is intended for network operations and security teams that manage their own flow collection infrastructure, rather than teams looking for a hosted monitoring service.
The suite covers NetFlow v5, NetFlow v9, IPFIX, and sFlow through its underlying components. Reports can be filtered by addresses, ports, interfaces, AS numbers, protocols, TCP flags, and next-hop values, with support for both IPv4 and IPv6 analysis. Graphs show bits per second, flows per second, and packets per second. Long-term views include peak, minimum, mean, and 95th-percentile values, while saved reports, saved filters, and dashboards support recurring operational monitoring. The documentation describes sFlow support through SiLK as available.
FlowViewer is free and open source, with no paid software tier described in its published pricing model. The vendor also offers paid installation, router configuration, training, and custom support services. Deployment is on premises, using a Unix server or virtual appliance, so the product fits teams prepared to operate their own flow environment. Choose it for basic flow reports, detailed filters, and long-term traffic graphs without a software license cost. Choose an alternative when verified application-level or conversation analysis is a central requirement, or when a hosted deployment is preferred.
FlowViewer pros and cons
- Where it wins
- Free, open-source flow reports with extensive filtering
- IPv4 and IPv6 analysis across several flow protocols
- Long-term graphs, saved reports, and operational dashboards
- Where it doesn't
- Requires exported flow data and an existing collection setup
- Designed for on-premises Unix servers or virtual appliances
- Does not provide verified application or conversation analysis
FlowViewer fact sheet, pricing and score →
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