Mettl Secure Browser: Requirements and What It Blocks

Mettl Secure Browser, or MSB, is the lockdown application Mercer Mettl uses when an employer wants the whole machine controlled rather than just the browser tab. As of September 9, 2026, Mettl documents it for Windows 7 and later with administrator rights and for macOS 10.14 and later. There is no Linux build and no mobile version. Once launched from the test link, it closes every other application, blocks other websites and blocked software, prevents screen mirroring, and does not let you leave until the test is submitted.

System requirements

Windows. Mettl's Windows MSB documentation states that "Windows MSB 12 will run on only windows (7 and above) and will support a minimum of 4.5.1. .NET framework." Three more requirements: "The candidate should have administrator rights on the system and not logged in as a Guest User," "MSB requires a 65 MB permanent free space on the default hard drive," and "The system's OS is up to date with no pending installations / updates."

macOS. The Mac install guide gives "Recommended MacOS: MacOS 10.14 and above." You open the .dmg, drag MSB to Applications, and confirm the security warning on first launch. It does not state whether the build is Intel, Apple silicon, or universal.

Not supported. Mettl's MSB test guide says "Mettl Proctored Assessments are not supported on Mobile devices (eg. Cellphone / Smartphones / Pads / Tablets)." No Linux installer is documented anywhere in Mettl's support center; Mettl's browser-based tests list Firefox on Linux, but MSB does not. A Linux user should ask the recruiter for the browser-based mode before the deadline.

Antivirus. Mettl's guidance is blunt. The MSB issues page says "Disable the antivirus in your computer before installing and launching the MSB," and the Windows documentation offers the alternative of adding MSB to the antivirus's trusted applications. Re-enable it afterward.

Permissions on macOS

MSB asks for the camera and microphone through the system prompt, documented in Mettl's camera and microphone guide, and for Screen Recording, documented in a separate screen recording guide that walks through Security & Privacy. Without the screen permission the test cannot capture your display, which is part of what proctoring records.

How to launch it

Install it once, then leave it alone. The MSB test guide warns: "do not open MSB by double clicking the application. MSB will be self-launched if you click on test link." The download itself comes from the invitation; the guide says to "Click on 'CLICK HERE' tab to download the Mettl Secure Browser (MSB) installation file." There is no app-store listing.

On launch, MSB "will prompt us to close any other application that may already be running on the computer." If it cannot close something, you are asked to end it in Task Manager. Save your work before you click the test link.

What MSB blocks

From Mettl's Windows documentation and the MSB test-taker guide:

• Leaving: "It does not allow the candidate to move out of the test window before the test is finished."
• Other software: MSB "shuts down all active applications and browsers" and "restricts from opening any unauthorized website or accessing any blacklisted software/third party applications."
• Switching: it "restricts access to different activities, such as switching to other websites and screens during the exam."
• Displays: it "does not allow sharing/mirroring of computer screens on any other display device."
• Exiting: "MSB ensures that test-takers cannot exit the application before the test is completed." The test ends when you finish it or when time runs out, at which point "your test will be auto completed and submitted."

Mettl's Start Assessing Better guide still labels the feature "Mettl Secure Browser (Beta)" and describes it as "a custom browser that temporarily lockdowns the computer to prevent the use of unauthorized resources during a test by controlling access to system functions, websites and applications."

What is not in the documentation matters too. Mettl's fetchable support pages do not describe virtual machine detection or remote-desktop blocking for MSB; a 2020 security document on mettl.com may, but it is not readable as text. Do not assume either direction.

What MSB captures

The same proctoring as the browser mode, inside the lockdown. Mettl requests the camera and microphone, requires your face and ID photos ("share your current image (capture using your webcam) and image of your required Identity Proof"), and captures the screen. The anti-cheating measures page documents snapshots "at every 60 seconds" and full webcam capture as options, and the eight AI flags apply. Details are in whether Mettl records your screen and whether Mettl uses your camera.

How MSB compares to other lockdown apps

Mettl's approach is a locked browser on a physical Windows or macOS machine with an administrator account. Other vendors ship the same idea with different limits; the general model and what to check before installing any of them is in when the coding assessment is an app, not a website.

What this means for candidates

Install MSB a day early on a machine you administer, update the OS first, and rehearse the launch from the link, not the icon. Use one display, unplug the rest, and close everything before you start; MSB will force-close what you forget. If you are on Linux, a managed work laptop without admin rights, or a tablet, tell the recruiter now. The complete list of what Mettl records across every tier is in what Mettl proctoring records and flags.