Runtime

How to run Selenium in a cloud sandbox

Pip-install selenium in an Ubuntu 24.04 microVM and let Selenium Manager fetch Chrome and chromedriver, or run a Grid container there.

On Runtime, Selenium needs no browser setup of its own. Selenium Manager, built into Selenium since 4.11, downloads Chrome for Testing and the matching chromedriver the first time a test asks for Chrome, and every sandbox is a Firecracker microVM with Python 3.12, Node.js 24 and sudo to receive them. Each test run gets a clean machine with no profile, cookies or downloads left by the last one, from $0.03125 an hour for 2 vCPU and 4 GiB while it waits (pricing). Selenium 4.49.0 was the current release on PyPI and npm on 25 September 2026.

Two ways to use a sandbox

Where the test code runs What runs in the sandbox Use it when
In the sandbox Python or Node, Selenium, Chrome CI jobs, agents, anything that should run remote
On your machine A Selenium Grid container, reached by you An existing suite that expects a Remote browser

Run a Selenium script in the sandbox

TypeScriptimport { writeFile } from "node:fs/promises";import { Sandbox } from "withruntime";const test = `import sysfrom selenium import webdriveroptions = webdriver.ChromeOptions()options.add_argument("--headless=new")driver = webdriver.Chrome(options=options)driver.get(sys.argv[1])driver.save_screenshot("home.png")print(driver.title)driver.quit()`;await using sbx = await Sandbox.create({ diskMiB: 8192, timeoutSeconds: 900 });const slow = { check: true, timeoutMs: 600_000 } as const;await sbx.exec(  "sudo apt-get update -qq && sudo apt-get install -y -qq fonts-liberation libasound2t64 " +    "libatk-bridge2.0-0t64 libcups2t64 libgbm1 libgtk-3-0t64 libnss3 libxss1",  slow,);await sbx.exec("pip install --quiet selenium==4.49.0", slow);await sbx.files.write("/workspace/home.py", test);const run = await sbx.exec(["python3", "home.py", "https://example.com"], slow);console.log(run.stdout);await writeFile("home.png", await sbx.files.read("/workspace/home.png"));
Pythonfrom withruntime import SandboxLIBS = ("fonts-liberation libasound2t64 libatk-bridge2.0-0t64 libcups2t64 "        "libgbm1 libgtk-3-0t64 libnss3 libxss1")with Sandbox.create(disk_mib=8192, timeout_seconds=900) as sbx:    sbx.exec(f"sudo apt-get update -qq && sudo apt-get install -y -qq {LIBS}",             check=True, timeout_ms=600_000)    sbx.exec("pip install --quiet selenium==4.49.0", check=True, timeout_ms=600_000)    sbx.files.upload("home.py", "/workspace/home.py")  # the script above    run = sbx.exec(["python3", "home.py", "https://example.com"],                   check=True, timeout_ms=600_000)    print(run.stdout)    sbx.files.download("/workspace/home.png", "home.png")

The first webdriver.Chrome() takes longer than later ones: that is Selenium Manager downloading the browser and driver into ~/.cache/selenium, which SE_CACHE_PATH moves. pip install needs no virtual environment; it installs to /workspace/.local (the sandbox environment).

The library names are Ubuntu 24.04's (t64 suffixes), checked on packages.ubuntu.com on 25 September 2026. For JavaScript, npm install selenium-webdriver@4.49.0 uses the same Selenium Manager and the same libraries.

Why not apt-get install chromium-browser

On Ubuntu 24.04, chromium-browser (version 2:1snap1-0ubuntu2) and firefox (1:1snap1-0ubuntu5) are transitional packages that install the Snap versions. Chrome for Testing, which Selenium Manager downloads, is a plain binary built for automation, so leave the browser to Selenium.

Drive a browser in the sandbox from your own test suite

Run Selenium's standalone-chrome image with Docker in the sandbox, forward its port 4444 to your machine, and point webdriver.Remote at it. Your tests stay where they are; only the browser moves.

Pythonfrom selenium import webdriverfrom withruntime import Sandboxwith Sandbox.create(disk_mib=10_240, timeout_seconds=3600) as sbx:    sbx.exec("sudo enable-docker", check=True, timeout_ms=600_000)    sbx.exec("docker run -d -p 4444:4444 -p 7900:7900 --shm-size=2g "             "selenium/standalone-chrome:4.48.0-20260905", check=True, timeout_ms=900_000)    sbx.exec("timeout 120 bash -c 'until curl -sf localhost:4444/status; do sleep 2; done'",             check=True, timeout_ms=180_000)    with sbx.forward_port(4444, local_port=0) as grid:        driver = webdriver.Remote(command_executor=f"http://127.0.0.1:{grid.local_port}",                                  options=webdriver.ChromeOptions())        driver.get("https://example.com")        print(driver.title)        driver.quit()
TypeScriptimport { Sandbox } from "withruntime";await using sbx = await Sandbox.create({ diskMiB: 10_240, timeoutSeconds: 3600 });await sbx.exec("sudo enable-docker", { check: true, timeoutMs: 600_000 });await sbx.exec(  "docker run -d -p 4444:4444 -p 7900:7900 --shm-size=2g selenium/standalone-chrome:4.48.0-20260905",  { check: true, timeoutMs: 900_000 },);const grid = await sbx.forwardPort(4444, { localPort: 4444 });const watch = await sbx.forwardPort(7900, { localPort: 7900 });console.log("Grid: http://127.0.0.1:4444  live view: http://127.0.0.1:7900/?autoconnect=1");// Run your suite against http://127.0.0.1:4444, then:await Promise.all([grid.close(), watch.close()]);

Port 7900 is the image's noVNC view of the browser; the project's README gives its default password as secret. The forward goes through Runtime's API with your key, so neither port is open to the internet (forward ports). Docker Hub images come through mirror.gcr.io first.

Limits worth knowing

  • Disk. Chrome for Testing plus its libraries fit in an 8 GiB disk; the Grid image with Docker needs more, and the free trial allows up to 10 GiB.
  • Time. A command's default timeout is 60 seconds. Give installs and whole suites timeoutMs, and the sandbox a timeoutSeconds longer than the run.
  • Ports. A trial sandbox reaches ports 80 and 443 only, which covers Selenium Manager's downloads and most sites under test. Paid sandboxes reach any port, such as a staging server on 8443.
  • Parallel runs. A paid account runs 100 sandboxes at once to start with; the trial runs eight. Split a suite by file across sandboxes and each shard gets its own browser.

Sources

Facts on this page were checked on 25 September 2026.

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