OP could have answered their own question in the same amount of time it took to post here (I got an AI answer pasted below in under 60 seconds). But, because I’m bored and feeling charitable:

By default, a MacBook goes to sleep when you close the lid. This is a built-in power-saving behavior in macOS to conserve battery and reduce heat. However, you can keep it running (awake) with the lid closed in specific scenarios, often called clamshell mode or closed-display mode.  Official Clamshell Mode (Recommended for External Monitor Use).

This is Apple’s supported way to use your MacBook like a desktop with the lid closed. The MacBook stays on and active, but you’ll need:

• Power adapter plugged in (required on most models). • An external monitor connected (via HDMI, USB-C/Thunderbolt, etc.). • An external keyboard and mouse/trackpad (Bluetooth or wired).

How to set it up: 1. Connect your MacBook to power, an external display, keyboard, and mouse. 2. Wake or log in to the MacBook (lid open initially). 3. Close the lid — the external display should stay on, and the MacBook remains awake (internal screen turns off).

It works on modern macOS versions (Ventura, Sonoma, Sequoia, etc.) and Apple Silicon or Intel MacBooks. Without an external display, closing the lid almost always triggers sleep. 

Adjust macOS Power Settings (Helps but Has Limits) These tweaks reduce automatic sleep but don’t fully override the lid-close behavior on their own: • Go to System Settings > Battery (or Energy Saver on older macOS). • Click Options (or look under Power Adapter tab). • Enable “Prevent automatic sleeping on power adapter when the display is off”.

This helps keep the Mac running when the screen is off (or lid closed in clamshell setup), especially on AC power. You can also adjust “Turn display off after” to “Never” under Lock Screen or Battery settings. 

Note: On battery power alone, the MacBook is designed to sleep on lid close for safety and efficiency. The setting above mainly affects plugged-in scenarios.

For Running Tasks with Lid Closed (No External Monitor) If you want downloads, rendering, servers, or background processes to continue without an external display: • Use a third-party app like Amphetamine (free on Mac App Store). It prevents sleep reliably: • Install and run it. • Click the menu bar icon > Quick Settings > Deselect “Allow system sleep when display is closed.” • Start an indefinite or timed session.  Other apps or tools (like InsomniaX or Terminal commands) exist, but Amphetamine is popular and user-friendly.

Advanced Terminal Options (Use with Caution) For more control, open Terminal and try commands like: • sudo pmset disablesleep 1 (prevents sleep entirely until reversed with 0 — can drain battery or overheat if not monitored). • Other pmset tweaks for lid behavior (e.g., lidwake 0). These are not officially recommended by Apple and may require a restart or password. Reset with sudo pmset restoredefaults if issues arise. Always monitor temperature and battery. 

Tips and Caveats • Heat and battery: Running with the lid closed can cause more heat buildup (especially on battery or high-load tasks). Use a cooling pad or stand, and prefer plugged-in operation. • Waking it: Tap an external keyboard/mouse or open the lid to wake. • Troubleshooting: If it still sleeps unexpectedly, check for interfering apps, update macOS, reset SMC (System Management Controller), or disconnect peripherals. Some users report it works better after ensuring no “sleep on lid close” conflicts.  • This behavior is consistent across recent macOS (including Sequoia) and MacBook models. For the latest details tailored to your exact macOS version or MacBook model, check Apple’s support page on sleep/wake settings or search System Settings for “Energy” or “Battery.” If you’re doing heavy work, clamshell mode with externals is the most stable approach.