Vertical video on a Mac

Social video is portrait. The Mac's bundled editor is not: iMovie locks projects to 16:9, so a vertical clip exports with black bars down both sides. The workarounds people share on Apple's own forums involve rotating the footage sideways, exporting, and rotating it back in QuickTime. If you are here, you have probably met that problem. Here is what actually works, including the tools we did not make.

Stay in iMovie - if your video is landscape

iMovie is free, already installed, and good at what it was built for: landscape movies. If you are cutting 16:9 for YouTube or a screen, there is no reason to leave it. For vertical output the rotate-export-rotate workaround does function, but you give up titles that read correctly during editing, and every export needs the extra QuickTime step. For an occasional clip, that can be fine. As a routine, it wears thin.

DaVinci Resolve - free and professional, with a learning curve

Resolve handles any aspect ratio: set the timeline to 1080×1920 and the format problem is gone. The free version is a full professional editor - which is both the recommendation and the warning. If you want colour grading, multi-track sound and an editing career's worth of tools, it is the strongest free choice on the Mac. If you want to put three clips, a caption and a music track together before lunch, it is a lot of application for the job.

CapCut - free, vertical by default, and the one most people already use

CapCut is the honest first answer for a lot of people, and leaving it out of a vertical-video guide would be silly. It runs natively on the Mac, opens straight into 9:16, has auto-captions, templates and trending audio, and the free tier covers an ordinary social edit without paying anything. It is made by ByteDance, the company behind TikTok, which is exactly why it fits TikTok so well.

The trades are worth knowing before you commit a workflow to it: it wants an account, a meaningful set of features sits behind CapCut Pro, and the AI and cloud features process your footage off your machine. Terms and free-tier limits have also moved more than once. If none of that bothers you, CapCut is free and very good at this job.

The subscription editors - a service, priced like one

The big social-video editors handle vertical natively and add cloud asset libraries, AI features and phone-and-web access. They are genuinely capable, and if you edit across devices every day the service model can earn its monthly price. That price is the trade: you are renting the workflow, the features shift with the plan tiers, and stopping the payment stops the tool.

PX7 Video Assemble - the ordinary social edit, owned

Our app covers one job: assemble clips and photos on a timeline, trim, add text, captions, voice-over and music, and export. Portrait 9:16, landscape 16:9, square 1:1 and portrait 4:5 are native project formats - no rotating, no bars. Captions are generated on your Mac, files never leave it, and there is no account. One payment - less than a single month of a video subscription - and it is yours, on up to seven Macs.

What it is not: a grading suite, a cloud asset library, or a phone app. If you need those, Resolve and the subscriptions above are the honest answers. Assemble is for the edit most social posts actually need, made by a person in Copenhagen who answers the support mail himself.

Try PX7 Video Assemble free for 7 days

The numbers, whichever tool you pick

Export 9:16 at 1080×1920. That is what TikTok, Reels and Shorts are built around, and anything else invites re-encoding, black bars or a crop you did not choose. For the other social shapes: 1:1 is 1080×1080 and 4:5 is 1080×1350.

Then leave room for the interface. Every platform lays its own buttons, captions and handle over your video, and they cover roughly the top tenth and the bottom fifth of the frame, with the right edge taken by the action buttons. Keep text and faces inside the middle - a rough rule that survives platform redesigns is to treat the outer 10% top, 20% bottom and 10% right as reserved. The most common vertical-video mistake is not the aspect ratio; it is a subtitle sitting exactly where the caption bar lands.

What each way of going vertical actually costs

"Just make it vertical" hides three different operations with three different prices. We measured them rather than describing them: a 1920×1080 test clip converted to 1080×1920 with ffmpeg 8.1.1 on macOS 26.5.2, Apple silicon.

• Scale it to 1080×1920. You get the right pixel dimensions and a distorted picture: the file comes out with a 256:81 pixel aspect ratio, meaning everything is stretched tall. This is the one that looks subtly wrong and nobody can say why.
• Fit it inside the frame with bars. Nothing is lost and nothing is distorted, but the picture occupies a 607-pixel band in a 1920-pixel frame — 32% of the screen is your video and 68% is black. That is the iMovie rotate-and-export workaround, and it is why those posts perform badly.
• Crop to 9:16. The frame stays full, and you keep 56% of the original width — 44% of your picture is cut away, taken off the sides. Fine for a centred subject, fatal for a two-person interview.

None of the three is free, which is the actual argument for shooting vertical or editing in a vertical timeline from the start: it is the only route that costs nothing. Measured 31 July 2026.

The short version

Landscape video, no budget: iMovie. Free and vertical out of the box, if an account and cloud processing are fine: CapCut. Full professional control: DaVinci Resolve. Cross-device service workflow: a subscription editor. The everyday vertical edit, on your own machine and without renting it: PX7 Video Assemble.