Short-form platforms are built for vertical video. TikTok, Instagram Reels, and YouTube Shorts all favour a 9:16 aspect ratio — and modern AI video generators now support it natively. Here is how to create scroll-stopping AI video for TikTok without cropping landscape clips or losing character consistency.
Why 9:16 matters for AI video
Shooting or generating in the wrong aspect ratio is the most common short-form mistake. A 16:9 cinematic clip cropped to vertical cuts off composition, loses detail, and looks amateur beside native vertical AI video. Generate directly at 9:16 and your characters stay centred, your backgrounds fill the frame, and your clips are ready to post without re-editing.
Which AI video models support 9:16
Not every engine outputs portrait video. As of 2026, these models commonly support 9:16 AI video:
- Google Veo — 9:16 and 16:9; strong cinematic motion
- Seedance (OpenRouter / BytePlus) — 9:16 plus additional ratios; excellent with multiple character references
- OpenAI Sora — portrait sizes (e.g. 720×1280)
- Kling — 9:16, 16:9, and 1:1
Pick the model first, then choose aspect ratio — the available options filter automatically so you never submit an unsupported combination.
Prompting for vertical composition
Vertical framing changes how you write prompts. Tips for TikTok AI video and Reels:
- Centre your subject. "Medium close-up, character centred in frame" works better than wide establishing shots.
- Use vertical depth. Stairs, corridors, tall trees, and city streets use the tall frame naturally.
- Keep text-safe zones in mind. Leave the bottom third slightly clear for captions and UI overlays.
- Favour close-ups for dialogue. Faces read better on phone screens than distant wide shots.
Short-form story structure
A 30–60 second AI short video needs a tighter arc than a YouTube upload:
- Hook (0–3 s) — one striking visual or action
- Build (3–20 s) — two or three scenes with the same character references
- Payoff (final 5 s) — twist, punchline, or cliffhanger
In Tomson Studio, each beat is one screen. Generate three to five vertical scenes, stitch them in episode order, and export — the whole AI Reels workflow runs in the browser.
Character consistency in vertical series
TikTok and Reels reward recurring characters and episodic formats. Create a reference sheet once, reuse it in every 9:16 scene, and enable continue from previous screen when you want motion to flow across a swipe-style cut. Viewers subscribe to characters, not one-off effects — consistency is what makes a series.
9:16 vs 16:9: when to use each
- 9:16 — TikTok, Instagram Reels, YouTube Shorts, Snapchat, mobile ads
- 16:9 — YouTube long-form, presentations, TV-style content
- 1:1 — Instagram feed posts, some ad placements
You can maintain the same project, characters, and script while exporting different aspect ratios per platform — generate a 9:16 version for Shorts and a 16:9 version for YouTube from the same storyboard with different screens.
Export checklist before you post
- Generated at 9:16, not cropped from landscape
- Duration under 60 seconds for Shorts; 15–30 s often performs best on TikTok
- Character references attached in every scene
- Watermark applied if branding your series
- Captions added in-app — most short-form views are sound-off