Can you put a GoPro or Osmo Action on the Osmo Mobile 6?

Not as a supported setup. The Osmo Mobile 6 is designed and balanced for smartphones that weigh 170 to 290 g and are 67 to 84 mm wide. A GoPro or DJI Osmo Action camera is lighter, smaller and a different shape, and DJI doesn't make an action-camera adapter for its phone gimbals. A third-party bracket won't change the load the motors are designed for, and you lose DJI Mimo features. Your action camera's own stabilization is usually the better tool.

Action cam on an OM 6? — DJI designs and balances the Osmo Mobile 6 for smartphones. Action cameras are below its weight range and DJI doesn't make an adapter, so results aren't supported.

Why it doesn't fit well

Weight. The Osmo Action 5 Pro weighs 146 g, below the Osmo Mobile 6's 170 g minimum. The Action 4 is 145 g, and GoPro HERO cameras are similar small, light blocks. That's outside the load range DJI designs the gimbal for.
Shape and balance. The magnetic clamp stretches across a flat phone 67 to 84 mm wide. An action camera is a small block with its lens off-center, so it won't sit centered.
No app control. DJI Mimo's tracking, zoom wheel, timelapse and gesture features use the phone's camera. With an action camera clamped on, none of those connect, and the shutter button won't trigger the camera.

What about a third-party adapter?

If you find a third-party bracket that holds an action camera like a phone, know that DJI doesn't test or support it, and the weight limits still apply. If you try one, keep the total within 170 to 290 g, center it, and expect mixed results. We don't recommend it as a substitute for the right tool.

Better options for smooth action-camera footage

Use the built-in stabilization. The Action 5 Pro's RockSteady 3.0 and 360° HorizonSteady handle walking, biking and helmet footage well. See horizon lock and tracking.
Stabilize in post. Record with EIS off and the FOV on Wide, then use Gyroflow.
Use a handle, not a gimbal. An extension rod or the Osmo Action Multifunctional Charging Handle gives a steady grip and controls.
Use a camera with a gimbal built in. The Osmo Pocket 3 has a 3-axis mechanical gimbal and a 1-inch sensor. See do you need a gimbal for an action camera.

When the Osmo Mobile 6 is the right pick

If the camera you want to stabilize is your phone, it's a great choice: magnetic clamp, 215 mm extension rod, ActiveTrack and about 6.4 hours of battery. Check your phone in Osmo Mobile 6 compatible phones.

Shop the Osmo Mobile 6 for your phone, or the Osmo Action 5 Pro for action and water.