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To capture a localhost site in a cloud browser, start the site on your computer, connect it to TestMu AI (formerly LambdaTest) with its secure tunnel, then open the tunneled address in the browser or screenshot workflow and capture the desired browser and viewport. A cloud browser cannot normally reach your machine’s private localhost by itself. Older guides may still use LambdaTest terminology.
Before you start
Run your website locally and confirm it loads in a browser on the same computer that will run the tunnel. There is no universal server command here: use the command and port for your framework, then note the local address and port your app uses. The tunnel workflow depends on a running, reachable local server; the documentation does not prescribe a framework-specific command or one universal localhost address.
Sign in to your current TestMu AI/LambdaTest account and select the local testing or screenshot workflow that matches your goal. Product interface labels can change, so follow the current instructions in your account rather than relying on button locations from an older guide.
Connect localhost to the cloud browser
The tunnel creates an encrypted link between your computer and the provider’s cloud machines. TestMu AI documentation describes TCP with TLS 1.2 over port 443 and WebSocket over port 443. Unless you explicitly set a mode, the tunnel binary scans the network and selects one.
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Choose a tunnel setup method
- Platform-specific binary: Download the binary for your operating system and machine architecture, then follow the current tunnel instructions. This is suitable for command-line use and automation.
- UnderPass: The vendor describes this graphical desktop app as a way to set up the tunnel without terminal commands.
- Integrations: The product page also lists an npm plugin and GitHub Actions integration for local testing. Check the current product instructions for their setup and availability.
The vendor’s published tunnel requirements include Windows 7 or later, macOS 10.12 or later, modern Linux distributions, FreeBSD or Solaris; x86_64 or ARM64; one physical CPU core; 2 GB RAM; 200 MB disk; permission to execute the binary; and outbound access to vendor servers over port 443. These are the vendor’s requirements, not independent performance measurements. Its documentation page says it was last updated September 11, 2026: Test locally hosted web pages.
Use the address expected by the tunnel
After starting the tunnel, open the local site through the address and port recognized by the tunnel configuration and current cloud-testing workflow. Do not assume that typing localhost into a remote browser points to your computer: localhost normally refers to the machine making the request. The official material confirms local-site access but does not provide one universal address, port mapping, or host alias for every setup. Use the current tunnel instructions for your configuration.
Capture the screenshot
- Keep your local server running and start the tunnel using the selected binary or UnderPass.
- In the local browser-testing or screenshot workflow, enter the tunneled local address specified by your configuration.
- Select the browser and device or viewport combination you need, then launch the session or screenshot capture.
- Inspect the result and share it if that option is available in your current workflow and account.
For responsive comparisons, capture the intended viewport or device matrix rather than treating one desktop image as proof of mobile behavior. The vendor’s screenshot-testing article says desktop-resolution selection applies to desktop devices and directs mobile checks toward responsive testing. It also discusses saved configurations, shareable results, and screenshots of pages behind login; those details come from a December 18, 2025 article and should not be treated as a guarantee that every historical control or feature remains unchanged. See the screenshot-testing overview.
Keep credentials and the tunnel safe
- Treat tunnel access keys and API tokens as private credentials. Do not expose them in public code, repositories, or environments.
- If a credential is exposed, revoke it and generate a replacement, as the vendor advises.
- Stop the tunnel when the testing session is finished.
The current local-testing product information is at TestMu AI local page testing.
Or skip the browser setup
If you only need a screenshot of a publicly reachable page, ScreenshotNeo provides a one-request screenshot API. It does not replace LambdaTest’s cloud-browser workflow for comparing browsers or devices, but it can avoid configuring a browser locally.
cURL example, using the documented endpoint and adapting the target URL:
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 options and response details. Cookie banners are accepted before capture and more than 60 known consent platforms, newsletter popups, and chat widgets can be removed; each step can be turned off. Bot checks, blank pages, timeouts, failed loads, and cache hits are not billed, and responses identify the page verdict and billing status. An MCP server gives AI agents tools for screenshots, page information, and PDF capture. The free plan includes 1,000 shots a month with no card; paid plans start at $5 for 3,000 shots. ScreenshotNeo is made by Yorker Media. Sign up for the free plan.
Troubleshooting
The cloud browser cannot open the local page
- Confirm the site loads on the same machine running the tunnel and that the server is still running.
- Check that you entered the address and port recognized by the tunnel configuration, not an assumed remote-machine
localhostaddress. - Check outbound network access to the vendor over port 443 and follow the current documentation’s tunnel mode and mapping instructions.
The tunnel will not start
- Verify that you downloaded a binary for the machine’s operating system and architecture and have permission to execute it.
- Check the published minimum requirements: one physical CPU core, 2 GB RAM, and 200 MB disk, along with outbound access over port 443.
- If network conditions prevent the selected connection mode, consult the vendor’s current instructions; the binary normally scans the network to choose a mode, while explicit mode selection is also possible.
The screenshot is blank or the page appears incomplete
- First load the local page in your own browser and confirm it has finished rendering. A tunnel cannot repair a stopped server or an application error.
- Check the exact local route and port used by the app. If only some routes fail, verify that the page’s assets and API calls are reachable in the cloud session too.
- If the problem persists, check the tunnel and session status in the current product workflow and consult the official support documentation.
A tunnel credential may have leaked
Revoke the exposed key or token and generate a new one. Remove the secret from public code and repositories; do not assume that deleting a visible copy makes an exposed credential safe.
Common choices and limits
| Decision | Use this when | Important qualification |
|---|---|---|
| CLI binary or UnderPass | Choose the binary for command-line setup and automation, or UnderPass if you prefer a graphical setup without terminal commands. | Both options and their instructions are subject to current vendor support and interface changes. |
| One-off screenshot or repeated browser/device checks | A one-off capture suits a quick visual check; a configured screenshot-testing workflow suits repeat comparisons across selected combinations. | Exact features and availability can depend on current account packaging; confirm them in the product. |
| Desktop viewport or mobile coverage | Use desktop resolution choices for desktop comparisons and responsive testing for mobile device combinations. | The vendor’s published guidance distinguishes these workflows; it does not establish a universal browser/device count. |
Current browser counts, free-plan limits, retention periods, and commercial entitlements are not established by the cited product material here, so check the account’s current plan and documentation before depending on them.
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