Mixer AI
Kling 4.0 Flash vs HeyGen Video: specs and price
Kling 4.0 Flash — maximum duration: 20 s; first frame: Yes. HeyGen Video — resolutions: 768p.
When to choose Kling 4.0 Flash and when HeyGen Video
Kling 4.0 Flash
- Maximum duration: 20 s vs 15 s for HeyGen Video
- Generation modes: from text / from first frame / from references vs from text for HeyGen Video
- First frame: Yes vs No for HeyGen Video
- Input photos: up to 7 vs up to 1 for HeyGen Video
HeyGen Video
- Resolutions: 768p vs 720p for Kling 4.0 Flash
- Prompt limit: 32,000 characters vs 8,000 characters for Kling 4.0 Flash
- Aspect ratios: 6 vs 5 for Kling 4.0 Flash
Key differences
Specifications
| Spec | Kling 4.0 Flash | HeyGen Video |
|---|---|---|
| Generation modes | from text / from first frame / from references | from text |
| First frame | Yes | No |
| Input photos | up to 7 | up to 1 |
| Input videos | up to 5 | No |
| Minimum duration | 3 s | 5 s |
| Maximum duration | 20 s | 15 s |
| Resolutions | 720p | 768p |
| Aspect ratios | 9:16 / 16:9 / 1:1 / auto / 21:9 | 9:16 / 16:9 / 1:1 / 4:3 / 3:4 / 21:9 |
| Prompt limit | 8,000 characters | 32,000 characters |
| Price, 1 s (different quality) | — coins · 720p | — coins · 768p |
There is no shared resolution for a direct price comparison, so each price includes its setting and is not highlighted as cheaper.
Price at the same settings
What to compare visually
For a fair A/B test, use the same scene and, where both modes allow it, the same first frame. Inspect motion continuity, character and object consistency, physics and contacts, camera behavior, temporal deformation, in-clip cuts and audio synchronization.
What to inspect with Kling 4.0 Flash
A lighter Kling 4.0: clips of 3–20 seconds in 720p from text and references, or from a start frame.
- Text and references: a prompt up to 8000 characters, up to 7 photos and up to 5 videos totaling up to 20 seconds; the Video sound switch keeps the sound of reference videos.
- Start frame: one optional photo; without it choose 16:9, 9:16, 1:1 or 21:9, with it the format follows the photo.
- Flash gives 720p and up to 20 seconds only; choose Kling 4.0 for 1080p and 30 seconds.
- Start frame mode accepts no video: videos belong to references mode only.
What to inspect with HeyGen Video
Creates videos with sound from a text prompt or a single source image.
- Text: the result is created from a written description.
- Every available setting is shown in the Studio form before launch, and the price follows them.
- The result length is 5 to 15 seconds.
- At most 1 photo as input.
How to run a fair comparison
- Fix the scene, the first frame (if both models accept one), the duration and the resolution.
- Judge motion, not stills: faces, hands and objects should hold across the whole clip and at cuts.
- If sound matters, listen to it separately: dialogue, effects and lip sync differ between models.
- Price a finished clip, not a second: the per-second rate times your real duration, rounded up once.
Sources
Prices, availability and specifications come from the Mixer AI catalog. This is not an independent test: try both models on the same task before choosing.
What we compare
FAQ
Which is cheaper: Kling 4.0 Flash or HeyGen Video?
The models use different settings, so a direct price comparison would be misleading: the prices of Kling 4.0 Flash and HeyGen Video are in the table, so compare for the mode you need.
How does Kling 4.0 Flash differ from HeyGen Video?
Kling 4.0 Flash — maximum duration: 20 s; first frame: Yes; input photos: up to 7. HeyGen Video — resolutions: 768p.
How should I compare Kling 4.0 Flash and HeyGen Video fairly?
Fix the scene, first frame, duration and resolution. Watch the motion across the whole clip and listen to the sound separately. Price the finished clip, not one second.
Are both models available in Mixer AI?
Yes. Both models are in the Mixer AI video catalog; the launch button on the page opens Canvas on a computer and the Studio on a phone. The page exists only for models in the current catalog.
Which model is better?
There is no single winner. First rule out the model that lacks the duration, first or last frame, sound or resolution you need, then compare clips on your own scene. The table highlights only measurable differences.