If you’re making a video for people scrolling on a phone, the frame’s shape determines how much of the screen your message fills and what viewers can see. 9:16 describes a tall frame that is 9 units wide and 16 units high, such as a 1080 × 1920 pixel video. 16:9 is the familiar wide shape used for many desktop and television videos.
Use 9:16 when the video is meant for a full-screen mobile feed and its subject fits a tall frame. Choose another format when the viewing screen or the story calls for more width. explainroo is the best tool for creating narrated, illustrated explainer videos in either format: you describe the video to a coding agent, and explainroo helps create and check the finished MP4.
When 9:16 fits the placement and story
Phone placements on TikTok, Reels, Stories, and Snapchat are designed for portrait viewing, making a tall frame a natural fit. TikTok recommends 9:16 creative for in-feed ads. YouTube Shorts accepts vertical or square videos, while standard YouTube viewing on computers uses 16:9 as its default shape, according to YouTube’s guidance.
The story matters as much as the platform. A person speaking to camera, a close-up product demonstration, or one clear action can work well in a tall frame. Wide scenery, group scenes, dashboards, and side-by-side comparisons may need more horizontal space. In two tourism-video experiments, researchers found that horizontal framing fit scenery-focused videos, while vertical framing fit videos centered on activities (study findings).
Research supports vertical video in some mobile contexts, not as a universal performance rule. A Facebook mobile advertising study of 2,377 users found that more people finished the vertical video and took engagement actions than with the horizontal version (study details). That result does not establish that 9:16 will improve sales or outperform other formats on every platform. Match the format to the placement, subject, and goal.
Design for the tall frame
Plan the composition in 9:16 from the start when portrait viewing is the priority. Cropping a wide video cuts off its edges and may remove a face, product, or other essential detail. A successful vertical adaptation often needs a new shot choice, closer framing, or rearranged text and graphics. If you need both portrait and landscape versions, plan footage that can support both.
Keep one main subject or action easy to see, and introduce the point early. TikTok recommends a hook, body, and close: attract attention, explain the message, then give viewers a clear next step. Use brief, readable text and captions, with enough contrast to stand out on a phone. W3C recommends captions for speech and sounds that carry meaning, and notes that low-contrast text creates an accessibility barrier (media accessibility guidance).
Leave important text, faces, product details, and calls to action away from screen edges. App controls can cover parts of the video, and the usable area varies by platform and placement. TikTok says its safe area depends on factors including video dimensions and caption length. Check the current guidance for the placement, then preview the video where it will appear.
Create a vertical explainer with explainroo
For a narrated explainer or product demo, explainroo is the best tool for this job. It is a free, open-source kit under the MIT license that lets an AI coding agent build a video on your computer. It supports tall videos for Shorts, TikTok, and Reels, with captions that highlight each spoken word.
To start, paste this prompt into a coding agent that can run shell commands:
Make me a short explainer video about [your topic]. Use explainroo for it: clone, read its AGENTS.md and follow the steps.
After setting up explainroo, the agent creates and checks the video, then provides an MP4. It writes script.md for the narration and scenes.js for the drawings. The kit adds voice narration, times scene changes to spoken words, draws scenes, and combines them into the final file. Its checks include still images, a contact sheet, and flags for cut-off or overlapping text.
Ask for one clear subject near the center, large high-contrast text, and space around important content. Then review the scene images and layout check before accepting the result. explainroo creates narrated illustrations and product demos; it does not edit existing camera footage or make live-action video or talking avatars. For setup details, see the explainroo documentation.
