4f16a6a035 | ||
---|---|---|
.. | ||
recipes | ||
architecture.md | ||
bug-labels.md | ||
configuration.md | ||
error-reporting.md | ||
hacking-tips.md | ||
headless-chrome.md | ||
lantern.md | ||
new-audits.md | ||
puppeteer.md | ||
readme.md | ||
releasing.md | ||
scoring.md | ||
throttling.md | ||
understanding-results.md |
readme.md
This directory contains useful documentation, examples (keep reading), and recipes to get you started. For an overview of Lighthouse's internals, see Lighthouse Architecture.
Using programmatically
The example below shows how to run Lighthouse programmatically as a Node module. It
assumes you've installed Lighthouse as a dependency (yarn add --dev lighthouse
).
const lighthouse = require('lighthouse');
const chromeLauncher = require('chrome-launcher');
function launchChromeAndRunLighthouse(url, opts, config = null) {
return chromeLauncher.launch({chromeFlags: opts.chromeFlags}).then(chrome => {
opts.port = chrome.port;
return lighthouse(url, opts, config).then(results => {
// use results.lhr for the JS-consumeable output
// https://github.com/GoogleChrome/lighthouse/blob/master/types/lhr.d.ts
// use results.report for the HTML/JSON/CSV output as a string
// use results.artifacts for the trace/screenshots/other specific case you need (rarer)
return chrome.kill().then(() => results.lhr)
});
});
}
const opts = {
chromeFlags: ['--show-paint-rects']
};
// Usage:
launchChromeAndRunLighthouse('https://example.com', opts).then(results => {
// Use results!
});
Performance-only Lighthouse run
Many modules consuming Lighthouse are only interested in the performance numbers. You can limit the audits you run to a particular category or set of audits.
// ...
const flags = {onlyCategories: ['performance']};
launchChromeAndRunLighthouse(url, flags).then( // ...
You can also craft your own config (e.g. mixed-content-config.js) for custom runs. Also see the basic custom audit recipe.
Differences from CLI flags
Note that some flag functionality is only available to the CLI. The set of shared flags that work in both node and CLI can be found in our typedefs. In most cases, the functionality is not offered in the node module simply because it is easier and more flexible to do it yourself.
CLI Flag | Differences in Node |
---|---|
port |
Only specifies which port to use, Chrome is not launched for you. |
chromeFlags |
Ignored, Chrome is not launched for you. |
outputPath |
Ignored, output is returned as string in .report property. |
saveAssets |
Ignored, artifacts are returned in .artifacts property. |
view |
Ignored, use the opn npm module if you want this functionality. |
enableErrorReporting |
Ignored, error reporting is always disabled for node. |
listAllAudits |
Ignored, not relevant in programmatic use. |
listTraceCategories |
Ignored, not relevant in programmatic use. |
configPath |
Ignored, pass the config in as the 3rd argument to lighthouse . |
preset |
Ignored, pass the config in as the 3rd argument to lighthouse . |
verbose |
Ignored, use logLevel instead. |
quiet |
Ignored, use logLevel instead. |
Turn on logging
If you want to see log output as Lighthouse runs, include the lighthouse-logger
module
and set an appropriate logging level in your code. You'll also need to pass
the logLevel
flag when calling lighthouse
.
const log = require('lighthouse-logger');
const flags = {logLevel: 'info'};
log.setLevel(flags.logLevel);
launchChromeAndRunLighthouse('https://example.com', flags).then(...);
Testing on a site with authentication
When installed globally via npm i -g lighthouse
or yarn global add lighthouse
,
chrome-debug
is added to your PATH
. This binary launches a standalone Chrome
instance with an open debugging port.
- Run
chrome-debug
. This will log the debugging port of your Chrome instance - Navigate to your site and log in.
- In a separate terminal tab, run
lighthouse http://mysite.com --port port-number
using the port number from chrome-debug.
Testing on a mobile device
Lighthouse can run against a real mobile device. You can follow the Remote Debugging on Android (Legacy Workflow) up through step 3.3, but the TL;DR is install & run adb, enable USB debugging, then port forward 9222 from the device to the machine with Lighthouse.
You'll likely want to use the CLI flags --disable-device-emulation --throttling.cpuSlowdownMultiplier
.
$ adb kill-server
$ adb devices -l
* daemon not running. starting it now on port 5037 *
* daemon started successfully *
00a2fd8b1e631fcb device usb:335682009X product:bullhead model:Nexus_5X device:bullhead
$ adb forward tcp:9222 localabstract:chrome_devtools_remote
$ lighthouse --port=9222 --disable-device-emulation --throttling.cpuSlowdownMultiplier=1 https://example.com
Lighthouse as trace processor
Lighthouse can be used to analyze trace and performance data collected from other tools (like WebPageTest and ChromeDriver). The traces
and devtoolsLogs
artifact items can be provided using a string for the absolute path on disk if they're saved with .trace.json
and .devtoolslog.json
file extensions, respectively. The devtoolsLogs
array is captured from the Network
and Page
domains (a la ChromeDriver's enableNetwork and enablePage options.
As an example, here's a trace-only run that reports on user timings and critical request chains:
config.json
{
"settings": {
"auditMode": "/User/me/lighthouse/lighthouse-core/test/fixtures/artifacts/perflog/",
},
"audits": [
"user-timings",
"critical-request-chains"
],
"categories": {
"performance": {
"name": "Performance Metrics",
"description": "These encapsulate your web app's performance.",
"audits": [
{"id": "user-timings", "weight": 1},
{"id": "critical-request-chains", "weight": 1}
]
}
}
}
Then, run with: lighthouse --config-path=config.json http://www.random.url