The infamous Black Bars are a common issue in OBS, directly related to aspect ratio. If the image is too small, it won’t be able to fill in the entire screen. As a result, the Black Bars will appear at the top and bottom, or left and right sides of the display capture. While it's not harmful, the bug is very unsightly. To fix this problem, you’ll have to adjust the aspect ratio so that the width and height of the image are compatible with the screen. As mentioned, you can do that by changing the Canvas and Output Resolution. The trick is to make the two match up: 1. Open OBS and click on “Settings” in the bottom-right corner of the screen. 2. Select the “Video” tab from the panel on the right-hand side. 3. Check if the aspect ratios for the Canvas and Output resolution match. If not, readjust accordingly. 4. Click “Apply.” One more thing you can try is adjusting the display resolution to match the Base and Output settings. Check out the previous sections for the steps to change the screen resolution on a Mac and PC.