The Tool Desk
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What you need before writing a browser test
- k6, installed on the machine or test environment where you will run the script.
- A Chromium-based browser. Grafana’s example uses Chrome.
- Basic JavaScript or TypeScript familiarity. Browser operations use asynchronous calls, so you will need
asyncandawait.
The k6 runtime is not Node.js, and compatibility with npm modules can vary. The first-test tutorial recommends using a code editor but does not require a particular editor or prescribe computer hardware. See Grafana’s browser testing documentation and first-test tutorial for installation details and current setup requirements.
Create and run a minimal browser test
You can generate a starting file with k6’s browser template:
k6 new --template browser browser-script.js
k6 run browser-script.jsOr create browser-script.js yourself. This example opens a page, checks that it has a non-empty heading, and closes the page even if navigation or the check fails:
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import { browser } from 'k6/browser';
import { check } from 'k6';
export const options = {
scenarios: {
ui: {
executor: 'shared-iterations',
options: { browser: { type: 'chromium' } },
},
},
thresholds: {
checks: ['rate==1.0'],
},
};
export default async function () {
const page = await browser.newPage();
try {
await page.goto('https://your-test-environment.example');
const heading = await page.locator('h1').textContent();
check(heading, {
'expected page is shown': (value) => value !== '',
});
} finally {
await page.close();
}
}Replace the example URL and heading assertion with your own application and a meaningful outcome. For example, a test of a sign-in flow should verify a signed-in state, not merely that the sign-in page loaded. The checks: ['rate==1.0'] threshold is an example that requires all checks to pass; it is not a universal performance target. Set thresholds to match your service objectives and test environment.
Build a user flow with locators
Use page.locator(...) to find and interact with the controls in your flow. Prefer locators over brittle assumptions about timing or element position: they are suited to dynamic pages, including single-page applications where content changes or frames navigate. Add checks for the result a user should see after an action, such as a confirmation message or a destination heading. Grafana documents browser interactions and locators in its interaction guide.
Always close the page
Put await page.close() in a finally block. This releases allocated resources and supports accurate Web Vital calculations, including when a navigation or assertion throws an error. Browser API operations are asynchronous in k6 starting with version 0.52.0; use async/await rather than treating them as synchronous calls. See the current browser API guidance.
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Choose browser, protocol, or hybrid testing
| Approach | What it tells you | Best fit |
|---|---|---|
| Browser-level | Whether a user-facing flow works and what browser-visible performance metrics it produces. | Frontend behavior, client-heavy applications, and checks that depend on actual browser interaction. |
| Protocol-level | How backend endpoints behave under request load. | Generating most of the traffic when you need substantial load efficiently. |
| Hybrid | How the application behaves under backend load while a user journey is sampled in a browser. | Combining broad protocol traffic with a smaller browser workload. |
Grafana’s guidance recommends using protocol requests for most generated traffic and fewer browser VUs for browser-level coverage where appropriate. Full browser instances are not automatically the most efficient way to generate large volumes of load. Choose based on the question you need the test to answer, rather than treating browser testing as a replacement for protocol testing. Read the k6 browser overview for Grafana’s discussion of the two approaches.
Recommended Free Tools
Run locally or in Grafana Cloud k6
Run locally
For local development and debugging, run:
k6 run browser-script.jsReview the checks and browser metrics in the command output, then adjust the script or thresholds to reflect the behavior you need to verify.
Run in Grafana Cloud k6
Grafana Cloud k6 supports cloud execution through its interface or CLI. Its results view can show browser-test information, including the 75th percentile of Web Vitals over time. Cloud configuration may include a load zone, test name, and project settings; consult the current Grafana Cloud browser execution documentation for the applicable setup.
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Grafana’s current documentation says browser VUs consume 10 times more VU hours than protocol VUs in Grafana Cloud k6. That comparison is specific to Grafana Cloud’s stated usage model; it does not describe local runs or other providers. Account for it when planning cloud test volume.
Read browser metrics without mistaking examples for targets
k6 browser results can include request metrics and Web Vitals such as FCP (First Contentful Paint), LCP (Largest Contentful Paint), CLS (Cumulative Layout Shift), INP (Interaction to Next Paint), and TTFB (Time to First Byte). Grafana’s documentation output demonstrates these metrics, but its displayed sample values are illustrative—not a benchmark or a recommended pass/fail value. Define thresholds from your own service objectives, test environment, and user expectations. Grafana describes browser metrics in its browser testing documentation.
Reliability and measurement practices
- Wait for a meaningful state. Prefer an element, navigation, or other relevant condition over arbitrary sleeps. The recommended practices cover waiting and common sources of unreliable tests.
- Handle consent banners and overlays. A cookie banner, newsletter popup, or chat widget can block the control your test needs. Make the test’s expected banner behavior explicit or use a suitable test environment.
- Account for dynamic elements and input delays. Applications may update or replace elements while the test runs. Use locators and wait for the state you intend to interact with instead of assuming the page is static.
- Keep metrics useful. Avoid unbounded time-series cardinality when adding dynamic labels or values; follow Grafana’s guidance for browser test metrics.
- Treat device presets as emulation. Presets can approximate mobile browser behavior, but they are not measurements from a physical device.
- Know the Cloud limitation. Environment-variable browser customization is unsupported for browser tests running in Grafana Cloud k6; check the current browser options documentation before relying on it.
Docker and Chrome sandboxing
If you run a local browser test in Docker, check the guidance for Grafana’s master-with-browser image before using it. The documented image warns about launching Chrome with no-sandbox; Grafana advises using that configuration only with trustworthy websites and documents a hardened alternative. Do not apply the no-sandbox setting indiscriminately to tests of untrusted sites. See the relevant browser setup documentation before adopting a container command.
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Troubleshoot common browser-test failures
| Symptom | Likely cause | What to check |
|---|---|---|
| The browser scenario will not start. | The browser scenario configuration is missing or malformed, or a Chromium-based browser is unavailable in the execution environment. | Confirm the scenario has an executor and options.browser.type is 'chromium'; verify k6 and the browser setup for that environment. |
| An operation returns before the page is ready or the script behaves as if it is synchronous. | Browser operations are asynchronous. | Use an async default function and await browser calls. The browser API is asynchronous starting in k6 v0.52.0. |
| A click or locator fails intermittently. | The page is dynamic, the target element changed, or a banner or overlay is blocking it. | Use a locator, wait for the intended state, and account for consent banners, popups, and chat widgets. Avoid arbitrary fixed sleeps when a state-based wait is available. |
| Web Vital results look inaccurate or resources accumulate. | The page was not closed reliably after a run. | Close it in a finally block so cleanup occurs on both success and failure. |
| A cloud browser test does not honor environment-variable customization. | That customization is unsupported for browser tests running in Grafana Cloud k6. | Use a supported browser option instead and verify current Cloud documentation for the setting. |
| A Docker browser run raises a Chrome sandbox concern. | The image’s documented launch configuration may use no-sandbox. |
Follow Grafana’s warning: use it only with trustworthy websites, or use the documented hardened alternative. |
Or skip the browser setup
If your goal is to capture a page rather than exercise an interactive k6 user journey, ScreenshotNeo provides a one-request website screenshot API. It returns PNG, JPEG, WebP, or PDF and also offers an MCP server for AI agents. It is not a replacement for k6 load testing or browser-flow assertions.
For example, this cURL request captures a page as WebP (replace the URL with your target):
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpSee the ScreenshotNeo API documentation for request options. Cookie and consent banners, newsletter popups, and chat widgets are removed before capture; each of those cleanup steps can be turned off. Bot checks and CAPTCHAs, blank pages, timeouts, failed loads, and cache hits are not billed, and response headers report the page verdict and billing status. AI agents can use its MCP server tools to take screenshots, get page information, and capture PDFs. The free plan includes 1,000 screenshots per month with no card; paid plans start at $5 for 3,000 screenshots.
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Frequently Asked Questions
Can I use TypeScript for a k6 browser test?
The first-test tutorial assumes basic JavaScript or TypeScript familiarity; use the current k6 guidance for the supported script setup.
Does a browser test replace a load test?
No. Browser testing checks user-visible behavior and frontend metrics; protocol traffic is generally better suited to generating most high-volume load.
Quick Recap
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