8 Best Performance and Load Testing Tools for Networks and Apps

The right performance and load testing tools depend on what you need to measure. A link test, generated WAN traffic, and simulated API users answer different questions. For networks, measure throughput, latency, packet loss, and jitter; for applications, track response time, request rate, and errors as load rises.

Test in a controlled, authorized environment: generated traffic can degrade service. Record the test setup, path, and competing traffic so you can interpret the result.

Choose a tool for the layer you are testing

Throughput is delivered data over time; it differs from a link’s rated bandwidth. Latency measures transit or response time, while jitter is variation in packet delay. Traffic generators create load but do not measure application behavior. Web load tools model requests, not raw Ethernet traffic.

Eight performance and load testing tools

1. iPerf3: measure IP network throughput

iPerf3 is a free command-line tool maintained by ESnet at Lawrence Berkeley National Laboratory. Run a server at one endpoint and a client at the other to measure achievable IP bandwidth. Configure duration, parallel streams, and TCP or UDP; results include throughput and UDP loss. It is a strong first check for a LAN, VPN, or WAN path, but does not model application sessions or disk speed.

2. LAN Speed Test: check file-transfer performance

LAN Speed Test measures transfers to a shared folder, which makes the result easy to relate to copying files to a NAS. That test includes storage and file-sharing overhead as well as the network. Totusoft also offers LAN Speed Test Server, which can test between computers’ memory to reduce disk bottlenecks. The vendor currently lists version 4.4 for Windows and macOS; its Lite mode is functional, with some advanced features disabled.

3. SolarWinds WAN Killer: generate controlled WAN traffic

WAN Killer, part of SolarWinds Engineer’s Toolset for the Desktop, generates random traffic to a selected target. Set the protocol, port, packet size, circuit bandwidth, and load percentage. It helps test link behavior or traffic prioritization under pressure; use a separate monitor to measure impact. This Windows component is not an end-to-end user test.

4. Ostinato: craft packet-level traffic profiles

Ostinato provides a graphical controller and traffic-generator agents for building multiple Layer 2 and Layer 3 streams, replaying packet captures, and varying send rates. It is useful for validating network devices, protocol handling, and custom traffic mixes. Its feature set varies by license, and the vendor notes that stateful TCP connections are not supported, so use another tool when your test depends on realistic TCP application sessions.

5. Cisco TRex: stress-test network devices at scale

Cisco TRex is an open-source, DPDK-based traffic generator with stateless and stateful modes. It targets engineers testing routers, firewalls, and other network equipment with high-volume profiles. Setup is more involved than with a throughput utility, so TRex fits a dedicated lab with compatible hardware and a defined test plan.

6. Apache JMeter: load-test services over common protocols

Apache JMeter is an open-source test application for web, API, database, messaging, and other services. Its test plans can model requests, data, assertions, and user concurrency. JMeter works at the protocol level; it does not execute JavaScript like a browser. Apache recommends running load tests in command-line mode rather than driving a heavy test from the GUI, then reviewing the generated results.

7. Grafana k6: script API workloads and performance limits

Grafana k6 is a code-first performance testing tool whose JavaScript-based scripts define requests, scenarios, and thresholds. Scenarios model different load patterns, while thresholds turn metrics such as request duration into pass/fail criteria that can run in CI. Choose k6 when test plans belong alongside application code and you want repeatable checks. Validate that the script represents real user behavior before treating its results as a production forecast.

8. Wireshark: inspect what happened on the wire

Wireshark captures and analyzes packets; it does not generate load or provide a standalone benchmark. Pair it with iPerf3, a traffic generator, or an application test to inspect retransmissions, protocol exchanges, and packet timing. Capture filters limit what is recorded, while display filters narrow what you see after capture. Choose the right network interface and capture point, and remember that you may need elevated privileges for live capture.

Quick picks

• Measure link throughput: start with iPerf3; use LAN Speed Test when file-copy performance is the question.
• Create network traffic: use WAN Killer for a straightforward controlled load, or Ostinato and TRex for custom packet profiles.
• Load-test an application or API: compare JMeter’s visual test-plan approach with k6’s code-first scripts.
• Investigate symptoms: capture with Wireshark while a repeatable test runs.

For comparable results, record endpoints, duration, protocol, and concurrent traffic. Repeat the same scenario after a change, while monitoring for network, server, storage, or client saturation.