Headless mode

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Headless模式是运行Firefox的一种非常有用的方式。就像听起来一样,Firefox正常运行,但没有任何可见UI组件。虽然不太适合浏览网页,但它对自动化测试非常有用。本文提供了有关运行 headless Firefox 的所有知识。

Using headless mode

This section provide usage instructions for headless mode.

Basic usage

You can run Firefox in headless mode from the command line, by including the -headless flag. For example:

/path/to/firefox -headless

Taking screenshots

Since Firefox 57, the -screenshot flag allows you to take screenshots of websites. The basic usage:

/path/to/firefox -headless -screenshot https://developer.mozilla.com

This creates a full-height screenshot of https://developer.mozilla.com, in the active directory called screenshot.png, with a viewport width of 800px.

You can omit -headless when using -screenshot, as it is implied:

/path/to/firefox -screenshot https://developer.mozilla.com

To override the default values, mentioned above, you can use the following flags/features:

  • -screenshot name url — Set a custom name for the screenshot by including it between the -screenshot flag and the URL you want to capture. You can specify other web-compatible image formats such as .jpg, .bmp, etc.
  • --window-size=x — Set a custom viewport width when taking the screenshot (full height is maintained). Note that the single argument version of this doesn't work.
  • --window-size=x,y — Set a custom viewport width and height to capture.

For example, the following command creates a screenshot of https://developer.mozilla.com, in the active directory called test.jpg, with a viewport width of 800px, and a height of 1000px:

/path/to/firefox -screenshot test.jpg  https://developer.mozilla.com --window-size=800,1000

Browser support

Headless Firefox works on Fx55+ on Linux, and 56+ on Windows/Mac.

Automated testing with headless mode

The most useful way to use headless Firefox, is to run automated tests. You can make your testing process much more efficient.

Selenium in Node.js

Here we'll create a Selenium test, using Node.js and the selenium-webdriver package. For this guide, we'll assume that you already have basic familiarity with Selenium, Webdriver, and Node, and you already have a testing environment created. If now, work through our Setting up Selenium in Node guide, and return when you have.

First, confirm you've installed Node and the selenium-webdriver on your system. Then create a new file, called selenium-test.js, and follow the steps below to populate it with test code.

Note: Alternatively, you could clone our headless-examples repo. This also includes a package file, so you can just use npm install to install necessary dependencies.

  1. Let's add some code. Inside this file, start by importing the main selenium-webdriver module, and the firefox submodule:

    var webdriver = require('selenium-webdriver'),
        By = webdriver.By,
        until = webdriver.until;
    var firefox = require('selenium-webdriver/firefox');
  2. Next, we create a new binary object representing Firefox Nightly, and add the -headless argument, so it will run in headless mode:

    var binary = new firefox.Binary(firefox.Channel.NIGHTLY);
  3. Now let's create a new driver instance for Firefox, using setFirefoxOptions() to include an options object, which specifies that we want to run the test using the above binary. This step will be unnecessary on Linux, and after headless mode lands in the release channel on Windows/Mac, but it is still useful if you want to test Nightly-specific features:

    var driver = new webdriver.Builder()
        .setFirefoxOptions(new firefox.Options().setBinary(binary))

    Alternatively, you can use options to set the binary and the headless arguments:

    var firefoxOptions = new firefox.Options();
    const driver = new webdriver.Builder()
  4. Finally, add the following code, which performs a simple test on the Google search homepage:

    driver.sleep(1000).then(function() {
    driver.sleep(2000).then(function() {
      driver.getTitle().then(function(title) {
        if(title === 'webdriver - Google Search') {
          console.log('Test passed');
        } else {
          console.log('Test failed');
  5. Finally, run your test with following command:

    node selenium-test

That's it! After a few seconds, you should see the message "Test passed" returned in the console.

Headless Firefox in Node.js with selenium-webdriver, by Myk Melez, contains additional useful tips and tricks for running Node.js Selenium tests with headless mode.

Selenium in Java

Note: Thanks a lot to nicholasdipiazza for writing these instructions!

This guide assumes you already have Geckodriver on your machine, as explained in  Setting up Selenium in Node, and an IDE set up which supports Gradle projects.

  1. Download our headlessfirefox-gradle.zip archive (see the source here). Extract it, and import the headlessfirefox folder into your IDE, as a gradle project.

  2. Edit the build.gradle file, to set selenium to a later version, if needed. At the time of writing, we used 3.5.3.

    group 'com.mozilla'
    version '1.0'
    apply plugin: 'java'
    sourceCompatibility = 1.8
    repositories {
    dependencies {
       testCompile group: 'junit', name: 'junit', version: '4.12'
  3. Edit the webdriver.gecko.driver property, in the HeadlessFirefoxSeleniumExample.java file, to equal the path where you installed geckodriver (see line 15 below).

    package com.mozilla.example;
    import org.openqa.selenium.By;
    import org.openqa.selenium.WebElement;
    import org.openqa.selenium.firefox.FirefoxBinary;
    import org.openqa.selenium.firefox.FirefoxDriver;
    import org.openqa.selenium.firefox.FirefoxOptions;
    import java.util.concurrent.TimeUnit;
    public class HeadlessFirefoxSeleniumExample {
     public static void main(String [] args) {
       FirefoxBinary firefoxBinary = new FirefoxBinary();
       System.setProperty("webdriver.gecko.driver", "/opt/geckodriver");
       FirefoxOptions firefoxOptions = new FirefoxOptions();
       FirefoxDriver driver = new FirefoxDriver(firefoxOptions);
       try {
         WebElement queryBox = driver.findElement(By.name("q"));
         queryBox.sendKeys("headless firefox");
         WebElement searchBtn = driver.findElement(By.name("btnK"));
         WebElement iresDiv = driver.findElement(By.id("ires"));
       } finally {
  4. Run the java class, and you should see the HTML content of this page printed in your console/terminal.

Selenium in Python

This guide assumes you already have geckodriver on your machine, as explained in Setting up Selenium in Node.

  1. Install the latest version of the Python client for Selenium.

  2. Edit the following, to set the executable_path on line 11, to the path where you installed geckodriver:

    from selenium.webdriver import Firefox
    from selenium.webdriver.common.by import By
    from selenium.webdriver.common.keys import Keys
    from selenium.webdriver.firefox.options import Options
    from selenium.webdriver.support import expected_conditions as expected
    from selenium.webdriver.support.wait import WebDriverWait
    if __name__ == "__main__":
        options = Options()
        driver = Firefox(executable_path='geckodriver', firefox_options=options)
        wait = WebDriverWait(driver, timeout=10)
        wait.until(expected.visibility_of_element_located((By.NAME, 'q'))).send_keys('headless firefox' + Keys.ENTER)
        wait.until(expected.visibility_of_element_located((By.CSS_SELECTOR, '#ires a'))).click()
  3. Run the Python script, and you should see the HTML content of this page printed in your console/terminal.

Other testing solutions

  • Slimerjs has Firefox support built in on Linux, with Mac and Windows support, coming soon. See Headless SlimerJS with Firefox by Brendan Dahl for more details.
  • TestCafe (v.0.18.0 and higher) also supports testing in headless Firefox, by default. See the documentation for the details.

In addition, you can use headless Firefox to run automated tests written in most other popular testing apps, as long as you are able to set environment variables.

Troubleshooting and further help

If you are having trouble getting headless mode to work, then do not worry — we are here to help. This section is designed to be added to as more questions arise, and answers are found.

  • On Linux, certain libraries are currently required on your system, even though headless mode doesn't use them, as Firefox links against them. See bug 1372998, for more details and progress towards a fix.

If you want to ask the engineers a question, the best place to go is the #headless channel on Mozilla IRC. If you are pretty sure you've found a bug, file it on Mozilla Bugzilla.

See also