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Runtime

How to run Selenium in a cloud sandbox

Install selenium with pip in an Ubuntu 24.04 microVM. Let Selenium Manager fetch Chrome and chromedriver, or run a Grid container there.

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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. Every sandbox is a Firecracker microVM with Python 3.12, Node.js 24 and sudo to install system libraries. Each test run gets a clean machine, with no profile, cookies or downloads left by the last one. A 2 vCPU, 4 GiB sandbox costs $0.03125 an hour while it waits (pricing). Selenium 4.51.0 was the current release on PyPI and npm on 25 October 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, and any code that should run remotely
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==4.51.0", 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==4.51.0", 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() call takes longer than later ones. In that call, Selenium Manager downloads the browser and driver into ~/.cache/selenium. SE_CACHE_PATH moves that folder. 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 in the Ubuntu archive's noble package index on 25 October 2026. For JavaScript, npm install selenium-webdriver@4.51.0 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. They install the Snap versions. Chrome for Testing, which Selenium Manager downloads, is a plain binary built for automation. 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:4.51.0-20261010", 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:4.51.0-20261010",  { 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 and its libraries fit in an 8 GiB disk. The Grid image with Docker needs more. Without credit, a sandbox has up to 10 GiB.
  • Time. A command's default timeout is 60 seconds. Set timeoutMs on installs and whole suites. Make the sandbox's timeoutSeconds longer than the run.
  • Ports. A sandbox without credit reaches ports 80 and 443 only. That 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 the same time. An account without credit runs four. Split a suite by file across sandboxes, and each shard gets its own browser.

Sources

Facts on this page were checked on 25 October 2026.

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of a 1 GB machine

  • No credit card
  • Four sandboxes at once, 2 vCPU and 4 GiB each
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