How to Change Aspect Ratio in iMovie on a Mac – and the Vertical Workaround

Learning how to change aspect ratio in iMovie is trickier than it sounds. Modern iMovie (version 10+) locks every project to a 16:9 canvas – there is no dropdown to switch to 9:16, 1:1, or 4:3. The built-in cropping tool lets you reframe footage, but it crops inside the 16:9 container, not resize the container itself.

To produce a true vertical 9:16 file (1080 × 1920) for TikTok, Instagram Reels, or YouTube Shorts, you need a workaround: either iMovie’s App Preview project type or a QuickTime Player rotation trick. This guide covers both the cropping method and the 9:16 workaround.

How to change aspect ratio in iMovie on a Mac

On a Mac, the only direct way to change the aspect ratio is through the Crop tool, which resizes the visible frame within the fixed 16:9 canvas. This removes black bars and fills the frame, but the exported file is always 16:9.

Step 1. Import your video

Open iMovie on your Mac. Create a new project or open an existing one. Click File > Import Media to import your video clip, or drag the file directly into the iMovie window. iMovie supports MP4, MOV, M4V, and other common formats. Drag the clip from the Project Media panel onto the timeline at the bottom of the window.

Step 2. Crop your video

Click on the video clip in the timeline to select it. In the preview window toolbar at the top, click the Crop icon (it looks like two overlapping rectangles or a set of cropping marks). The controls appear above the preview: Fit, Crop, and Ken Burns. Select Crop to Fill to enlarge the video so it fills the 16:9 frame without black bars, or Fit to keep the entire frame with black bars on the sides for portrait footage.

Step 3. Adjust the frame

When Crop to Fill is selected, a yellow rectangle appears over the preview. Drag the corners and edges of the rectangle to define the crop area. Drag the rectangle itself to reposition the visible region. This is how you reframe vertical or oddly-shot footage to center the subject in the 16:9 output. When the crop looks right, click the blue check mark (Apply) in the top-right corner of the preview.

Input formats supported by iMovie

iMovie accepts the following video and audio formats for import.

How to get a true 9:16 vertical video from iMovie (workaround)

iMovie’s timeline is locked to 16:9. To export a true vertical 1080 × 1920 file, you need this two-part workaround using iMovie’s App Preview project type and QuickTime Player.

Step 1. Start a new project

In iMovie, go to File > New App Preview. This creates a project type designed for portrait mode app store previews, which forces iMovie into a vertical 9:16 canvas. Add a vertical video clip or a portrait photo as the first item on the timeline to set the project ratio to 9:16, then drag your main footage after it. Delete the placeholder clip and use the Crop tool to center your subject in the vertical frame.

Step 2. Export and rotate in QuickTime Player

Click File > Share > File to export the project from iMovie. In the export dialog, select 1080p as the resolution. Open the exported file in QuickTime Player. Go to Edit > Rotate Left (or Rotate Right, depending on your clip’s orientation) to correct the rotation. Then go to File > Export As > 1080p to save the final vertical 1080 × 1920 file.

Output formats supported by iMovie

iMovie exports to these video formats after aspect ratio adjustment.

Aspect ratio limitations in iMovie

❌  No aspect ratio selector: iMovie 10+ removed the File > Project Properties > Aspect Ratio menu. The only ratio is 16:9.

❌  No true 9:16 native support: vertical 9:16 output requires the App Preview project + QuickTime rotate workaround.

❌  No 1:1, 4:5, or 4:3 support: custom ratios for Instagram feed (4:5) or square (1:1) are not available in iMovie at all.

❌  Crop only, no canvas resize: every ratio change in iMovie is a crop inside the 16:9 canvas, not a true canvas resize.

Alternative: Movavi Video Editor

Movavi Video Editor is the practical alternative to iMovie for changing aspect ratio. It includes a one-click canvas resize to any standard ratio – 16:9, 9:16 (vertical), 1:1, 4:3, 4:5, and custom dimensions – with no workarounds, no QuickTime rotation, and no crop-only restriction. Works on footage from any camera or device.

Movavi Video Editor is available on both Windows PC and Mac, making it the right tool for creators who work across platforms or need ratios iMovie simply doesn’t support.

How to change aspect ratio using Movavi Video Editor

Three steps from any footage to a true vertical 9:16 or any other ratio on your Mac or Windows PC.

Step 1. Install Movavi Video Editor and import your video

Download and install Movavi Video Editor for Windows or Mac. Open the app and click Add Files to upload your video. Drag it onto the Timeline at the bottom of the screen.

Step 2. Change the aspect ratio

In the Aspect ratio dropdown list under the preview window, select your target ratio: 9:16 for TikTok/Reels/Shorts, 16:9 for YouTube, 1:1 for Instagram feed, or Custom aspect ratio to type in specific dimensions (e.g., 1080 × 1920 for 9:16). The preview canvas immediately resizes to the new ratio.

Step 3. Export your clip

When the framing looks right, click Export. Choose the output format, pick a save location, and click Start.

Conclusion

Changing the aspect ratio in iMovie means cropping within a fixed 16:9 canvas using the Crop to Fill tool. To get a true vertical 9:16 file, the App Preview project + QuickTime Player rotation workaround produces clean results without quality loss.

When you need true canvas resizing to 9:16, 1:1, 4:5, or any custom ratio without workarounds, Movavi Video Editor handles it in three clicks on both PC and Mac. Download the free trial and produce the correct ratio for every platform from the same source footage.

Frequently asked questions

How do I resize a video in iMovie?

To resize a video in iMovie on a Mac:

1. Select the clip in the timeline.
2. Click the Crop icon in the preview toolbar and choose Crop to Fill.
3. Drag the yellow crop rectangle to the area you want to keep.
4. Click the blue Apply checkmark.

This resizes the visible frame by cropping – the output file is always 16:9. For a true canvas resize to a different ratio – like vertical 9:16 for TikTok – use the App Preview workaround described in Section 3, or use a dedicated tool like Movavi Video Editor, which resizes the canvas in one step without cropping workarounds.

How do I change iMovie from 1920 × 1080 to 1080 × 1920?

iMovie cannot natively export a true 1080 × 1920 vertical file from its standard project mode.

Here’s the workaround:

1. In iMovie, go to File > New App Preview to create a portrait mode project.
2. Add a vertical clip or image first to set the canvas to 9:16, then add your main footage.
3. Export at 1080p.
4. Open the exported file in QuickTime Player, go to Edit > Rotate to correct the orientation, then File > Export As > 1080p.

The result is a 1080 × 1920 vertical file. Alternatively, import your 1920 × 1080 file into Movavi Video Editor, set the aspect ratio to 9:16, reposition the clip, and export – no rotation tricks needed.

How do I set a 9:16 ratio in iMovie?

iMovie’s standard project type is fixed at 16:9 and does not have a 9:16 ratio option.

Here’s the cleanest way to set vertical 9:16 in iMovie:

1. Go to File > New App Preview – this creates a project type that forces a vertical portrait canvas.
2. Add a vertical image or video first to anchor the 9:16 ratio, then place your main footage after it.
3. Delete the placeholder and use the Crop tool to reframe.
4. Export via File > Share > File and rotate in QuickTime Player if needed.

For a simpler approach without any workaround, Movavi Video Editor includes a 9:16 preset that sets the canvas directly, works on Mac and Windows PC, and is free to try.

Why is iMovie changing the aspect ratio of my video?

iMovie forces every project to a 16:9 canvas. When you import a clip with a different aspect ratio – such as a vertical 9:16 video, a square 1:1 clip, or a 4:3 recording – iMovie either adds black bars (letterboxing or pillarboxing) or crops the edges to fill the 16:9 frame, depending on whether Fit or Crop to Fill is applied. This is iMovie’s default behavior and cannot be turned off in the current version. The resolution of the first clip you import sets the project resolution (e.g., 4K or 1080p), but the ratio always stays 16:9. If iMovie is cropping your footage unexpectedly, check the Crop setting on each clip (click the Crop icon in the preview toolbar) and switch it from Crop to Fill to Fit to show the full frame with black bars instead.