AI Generation

Keyframes in AI Video: First Frame and Last Frame

Also called first frame, last frame, start frame, end frame, first-last frame

A keyframe is a frame you fix in advance so the model has to pass through it. In AI video the two that matter are the first frame and the last frame, and supplying either one converts an open-ended generation into a constrained one. It is the single biggest lever on consistency.

Why a fixed frame changes everything

An unconstrained text-to-video generation has to decide what the subject looks like and how it moves. Those two decisions interfere. As the clip progresses, small appearance drift compounds, and by second four the subject can be visibly a different person.

Fixing a frame removes the first decision. The model no longer gets a vote on what things look like; it only has to produce motion consistent with a frame it was handed. That is why keyframe conditioning is the most reliable consistency tool available, and why it usually beats adding more descriptive words to the prompt.

The three modes

  • First frame only. The clip starts from your image and moves forward. The most common mode: maximum look control, with motion still exploratory.
  • Last frame only. The clip arrives at your image. Useful when the destination is what matters, such as landing on a product shot or a title card.
  • First and last frame. The model interpolates between two fixed images. The tightest control available, and effectively a different task, because you are specifying a transition rather than a shot.

The first-last frame mode is also the one that fails most visibly. If the two images are too far apart in content, the model has to invent an implausible path between them, and you get a morph rather than a move.

Chaining clips into a sequence

Most models cap a single generation at a few seconds. To build something longer:

  1. Generate clip 1 from a first frame.
  2. Export clip 1's final frame.
  3. Pass that frame as clip 2's first frame.
  4. Repeat.

Because consecutive clips share an actual frame rather than a description of one, the joins are continuous instead of merely similar. The tradeoff is drift across the chain: quality degrades slowly as each clip inherits the previous one's compression and artifacts. On long sequences, re-anchor with a freshly generated image every few clips.

Writing the prompt alongside a keyframe

When a keyframe is supplied, spend the prompt on motion, not appearance. The appearance is already decided, and re-describing it competes with the frame you provided.

  • ✅ camera slowly dollies forward, subject turns to face the light
  • ⚠️ a woman in a red coat in an alley restates what the frame already fixes

One more habit worth building: keep the source images. A first frame is a reusable asset. When a clip comes out wrong, regenerating from the same anchor with a different motion prompt is far faster than starting over, and it keeps the whole sequence visually consistent.

Models that support this

Pulled from the live ZOOOP model catalog, so this list stays current as new models ship.

See all 33 models

The prompt for this

A starting point that reliably produces the effect. Adjust the subject and setting; keep the technical clauses.

Camera slowly dollies forward down a wet cobblestone alley at dusk; hold the framing and grade of the supplied first frame

Try Keyframe yourself

Open the generator with a starting point already filled in.

AI First & Last Frame Video

Frequently asked questions

What is the difference between a first frame and a last frame?
A first frame pins where the clip starts, so the model only has to invent forward motion. A last frame pins where it ends, so the model has to solve a path to a known destination. Supplying both turns generation into interpolation between two fixed points.
Does supplying a keyframe improve consistency?
Substantially. Identity drift happens because nothing anchors the subject's appearance. A first frame is that anchor, and it is usually the cheapest fix for a subject that changes appearance mid-clip.
How do I make a video longer than one generation?
Chain clips: take the last frame of clip N and pass it as the first frame of clip N+1. Each clip stays within the model's length limit, and the seam is continuous because both sides share a real frame.
Is this the same as a keyframe in traditional animation?
The idea is the same, a fixed pose the sequence must pass through with the frames between filled in. What differs is who fills them: an inbetweener in animation, a model here.
Which models accept a first-last frame input?
Not all of them. The list on this page is generated from the live ZOOOP model catalog, so it reflects what currently accepts a start-frame input rather than a hand-kept list that goes stale.

Related terms

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