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Pagespeed Lab Test Simulator

Attempts to mimic Pagespeed Lab tests (lighthouse section) by setting machine specific slowdown settings, allowing easy calibration.

Other features:

  • Project configurations ( config folder )
  • Block static resources with the blocked_patterns setting ( example Analytics, Trackers, etc )
  • Reports are saved in the reports folder
  • Auto Calibration ( WIP )

Requirements:

  • Google Lighthouse requires Node 18 LTS (18.x) or later.

Instructions:

  • Copy example_project.cfg configuration file in ./config, rename and change settings

Run lighthouse test for Mobile:

bash performance example_project

Run lighthouse test for Desktop:

bash performance example_project desktop

Simulated Slowdown

Tweak slowdown factor in config/{project}.cfg. Pagespeed uses a simulated slowdown of 4x for mobile tests, and no slowdown for desktop.

The approximate hardware difference between the pagespeed and a M3 Pro processor is near 10x so by adjusting the config to:

# Adds 10 to slowdown
mobile_slowdown=14
desktop_slowdown=10

The lighthouse scores become similar to Pagespeed

Blocking Assets

We can block assets by adding them to the blocked_patterns list in config/config.cfg.

For example we can block trackingware by adding:

blocked_patterns+=(
    "googletagmanager"
    "doubleclick.net"
)

Pagespeed Default Settings

Mobile

{
    "onlyCategories": [
        "performance"
    ],
    "channel": "lr",
    "formFactor": "mobile",
    "locale": "en-US",
    "screenEmulation": {
        "deviceScaleFactor": 1.75,
        "height": 823,
        "mobile": true,
        "width": 412
    },
    "throttling": {
        "downloadThroughputKbps": 1474.5600000000002,
        "requestLatencyMs": 562.5,
        "rttMs": 150,
        "throughputKbps": 1638.4,
        "uploadThroughputKbps": 675,
        "cpuSlowdownMultiplier": 4
    },
    "throttlingMethod": "simulate"
}

Desktop

{
    "extends": "lighthouse:default",
    "settings": {
        "onlyCategories": [
            "performance"
        ],
        "channel": "lr",
        "formFactor": "desktop",
        "locale": "en-US",
        "screenEmulation": {
            "deviceScaleFactor": 1,
            "height": 940,
            "width": 1350,
            "mobile": false
        },
        "throttling": {
            "rttMs": 40,
            "throughputKbps": 10240,
            "cpuSlowdownMultiplier": 1
        },
        "throttlingMethod": "simulate"
    }
}