AI Video Generator for YouTube Shorts: Specs, Rules and Prompts

An AI video generator for YouTube Shorts makes the vertical footage; you bring the idea, the script and the voice. Toybox AI's Video Creator makes clips in Vertical (9:16), the shape YouTube treats as a Short, at 4, 6 or 8 seconds each, from a written prompt or a starting photo. The clips are the easy part. YouTube's disclosure and inauthentic-content rules decide whether a Short can earn money, and they're covered below with the specs, faceless formats, hook prompts and thumbnails.

What YouTube counts as a Short

On a standard channel, YouTube treats any video uploaded since October 15, 2024 as a Short if it has a square or vertical shape and runs up to three minutes. These are the numbers to plan around, from YouTube Help as of September 2026:

In Video Creator, choose Vertical (9:16), which the tool labels "TikTok, Reels". The same clip works as a Short, a Reel and a TikTok video.

Uses for an AI video generator for YouTube Shorts

An AI video generator for YouTube content works best as the picture under something only you can add: a script, a voice, a real opinion. These uses fit clips of 4 to 8 seconds:

• Scene illustrations for narrated stories. A lighthouse keeper's storm, a medieval market at dawn, a submarine descending. You narrate; each sentence gets its own clip.
• B-roll for talking-head Shorts. Cut away from your face to a clip of the thing you're describing, then back.
• Explainer visuals. The water cycle, a volcano from the inside, how a lock and key work, shown as short animated shots while you explain.
• Product teasers for your own shop. A slow reveal of a new item for a Shorts ad or post; the product ad walkthrough has a shot list.
• Intros and channel bumpers. A 4-second branded opener you reuse, with the logo added as text in your editor.
• Photos brought to life. Start from your own photo with "Start from a photo"; the page on animating a still photo has motion prompts by photo type.

Faceless Shorts ideas that stay monetizable

Showing your face isn't on YouTube's Partner Program eligibility list, but the monetization policies do exclude mass-produced content. YouTube renamed its "repetitious content" policy "inauthentic content" on July 15, 2025, and it excludes from monetization AI-made videos built from generic templates that feel mass-produced without the creator's own insight. It also rules out image slideshows, templated storylines and scrolling text with little or no narrative. A recurring series is allowed when each video has its own story or focus.

These faceless formats build in the original part YouTube looks for:

1. "One minute of history" with your research. You write and voice the story of one real event; AI clips show the setting (ships, streets, weather), never invented footage of real people.
2. Nature facts with a narrator. One surprising fact per Short, such as how an octopus changes color, with a close-up AI clip for each step.
3. An original character series. A fictional robot gardener or a cat detective, with a new plot each episode and the same look, made from the same start image.
4. How-to Shorts with real hands. Your own footage of a recipe or a repair, with AI clips only for the parts you can't film, like the inside of an engine.
5. Local guides. Your voice on a town's history over AI scenes of how the harbor or main street might have looked, said out loud to be an illustration and disclosed under "AI use" if it looks real.

YouTube's rules for AI-made Shorts

Creators must tell YouTube when realistic-looking content was made or meaningfully altered with AI. That covers putting words or actions on a real person that never happened, editing footage of a real place or event to show something else, and inventing a realistic scene that never took place.

• How to disclose. In YouTube Studio's upload flow, under Attributes, select "Yes" for "AI use". YouTube then labels the video, and photorealistic content may also get a label in the player.
• What doesn't need it. Clearly unrealistic scenes (someone riding a unicorn), color and beauty filters, and production help such as an AI-written script, captions or a thumbnail.
• Automatic labels. YouTube may label content made with its own AI tools, files carrying C2PA metadata, and content its systems detect as AI-made.
• What happens if you don't. Creators who repeatedly skip disclosure can get a label added for them, have content removed, or lose their place in the YouTube Partner Program. YouTube says disclosing doesn't limit a video's audience or its eligibility to earn money.

Hook prompts for the first seconds

The opening shot has one job: show something moving before the viewer swipes. Run them in Video Creator with Format set to Vertical (9:16). Each starts mid-action with one clear subject.

Vertical macro shot of a glass of water on a kitchen counter. A single drop falls from above in slow motion and hits the surface, sending up a crown of water. Static camera, bright window light from the left, dark background, crisp detail.

Vertical shot, camera rushing low over dark ocean waves at dusk toward a lighthouse on a rocky point, its beam sweeping across storm clouds. Rain streaks past the lens. Dramatic, cinematic, cold blue tones with the warm light of the lamp.

Vertical extreme close-up of an octopus on a coral reef as its skin shifts from sandy brown to deep red in a wave of color. Shallow depth of field, soft underwater light, particles drifting in the water, slow push in.

Vertical shot of a small round robot with a watering can, stepping carefully between rows of glowing mushrooms in a greenhouse at night. It stops and looks straight into the camera. Soft cinematic lighting, gentle mist, stylized 3D animation look.

For more scenes to adapt, browse the Veo prompt library, and switch the format to Vertical before you run any of them.

Tips for better AI Shorts

1. Write the voiceover first. Time it, then plan one clip per sentence or two. Clips follow the script, not the other way around.
2. Reuse one start image for a series. Make your character or setting once, then start each clip from that image so episodes look alike.
3. Keep text off the clips. Titles and captions belong in your editor's text tool, which keeps them crisp. Generated letters can warp as the picture moves.
4. Decide which sound comes from the clip. Video Creator clips come with sound, and there's no separate setting for it, so describe ambience or music in the prompt. When your own voiceover runs across several clips, ask for quiet background sound only and lower the clips' audio under your voice. The page on sound for AI video covers both.
5. Keep the subject near the center. Leave the edges of the frame for on-screen buttons and captions, and ask for the subject "centered in the frame" in the prompt.
6. Check the ending loops cleanly. A Short that ends on a frame close to its opening replays smoothly; an end frame that matches your start image makes this easier.

Thumbnails for Shorts and long videos

A Shorts thumbnail should be 9:16. YouTube recommends 2160 x 3840 pixels for a custom Shorts thumbnail, and it replaces a 16:9 custom thumbnail on a vertical video with an auto-generated 4:5 one in the home feed, Explore and Subscriptions. So the tool depends on the video:

• Long videos (16:9). Give YouTube Thumbnail Generator a description, or up to 80 characters of hook text, and optionally your photo, and it returns one thumbnail. It currently costs 80 credits on the Free plan, and every result is 16:9, never vertical.
• Shorts (9:16). Export a still frame from your editor as a JPG or PNG, upload it to Smart Editor, and set the Shape to Story (9:16) and the quality to 4K, which outputs 2160 x 3840 pixels, the size YouTube recommends. Type the title text you want into "What should change?". Smart Editor is a Pro tool, currently 110 credits at 4K. Because it redraws the entire frame, proofread the title and look closely at any face before you upload.

Either way, the same basics apply: a single subject, a few big words, and high contrast. The guide on what makes a good thumbnail goes through them with examples.

Where AI clips fall short for Shorts

• Each clip is short. Video Creator makes 4, 6 or 8 seconds per clip; a Short of 30 seconds or more always means cutting several clips together.
• Resolution. Video Creator makes 720p clips, below the 1080p YouTube accepts for Shorts. Video Creator Lite offers 720p or 1080p, and 1080p clips are always 8 seconds.
• Faces and text can drift. Toybox doesn't guarantee that text stays sharp while it moves. Keep generated clips free of words, and check faces at full screen.
• Cost adds up per clip. Every clip is charged separately: currently 350 credits in Video Creator, and 180 (720p) or 220 (1080p) in Video Creator Lite, with both tools on Pro plans and up. A 30-second Short built from four 8-second clips comes to 1,400 credits in Video Creator, more than the 1,000 a Pro plan includes each month, or 880 in Lite at 1080p. Check Toybox's pricing page for current numbers.

How to make a YouTube Short with Video Creator

1. Write and time the voiceover. Split it into lines of 4 to 8 seconds, one clip per line.
2. Go to Video Creator with a Pro plan. Video Creator Lite offers the same Format and Length choices for fewer credits, which suits drafts.
3. Set Format to Vertical (9:16) and choose a Length of 4, 6 or 8 sec for the line.
4. Describe the shot in "Describe your video". Start mid-action, name one subject, and add the camera move. Add a start image with "Start from a photo" if the series has a recurring character.
5. Press "Create video". Each clip needs a few minutes to render. Unsaved clips stay in Recent for 24 hours; save the ones you'll use.
6. Assemble the Short. Join the clips in a video editor, then add your voiceover, captions and title text, with the clips' own sound set lower than your voice.
7. Upload and disclose. In YouTube Studio, set "AI use" to "Yes" if the Short looks realistic, and add a 9:16 thumbnail on a computer.