Kling 4.0

Overview

The Kling 4.0 text-to-video route is designed for developers who need to produce finished clips directly from plain text descriptions. Enter a prompt describing the subject, action, camera movement, and lighting, and you get a video clip that includes both visuals and audio. A single clip can be set to any duration from 3 to 30 seconds, output supports 720p and 1080p, and you can choose from four aspect ratios: 16:9, 9:16, 1:1, and 21:9. It suits teams producing ad spots, vertical social media content, and storyboard previews, and is called through the unified HiAPI.ai interface with billing based on output seconds.

Key Highlights

• A single generation covers 3 to 30 seconds — duration is specified directly as a request parameter, so long shots don't need to be split into multiple segments and stitched together, reducing post-production alignment work.
• Visuals and audio generated together — the scene described in the prompt is produced along with its sound, eliminating a separate voiceover or sound effect step.
• Four aspect ratios for different distribution channels — in addition to landscape and portrait, 1:1 and 21:9 are also available, so you can select the output ratio for a platform placement in one go.
• Switchable resolution on demand — both 720p and 1080p are available; iterate at lower resolution during the draft stage, then raise the clarity for the final version.

Capabilities

Describe shots with long prompts: prompts can be up to 2500 characters, enough to hold a complete description of subject, action, camera movement, lighting, and atmosphere, letting a single request express more complex shot intent.

Parameterized duration control: duration values range from 3 to 30 seconds, and billing is based on output seconds. Short clips and long shots use the same interface, making it easy to allocate cost according to content pacing.

Two-tier resolution output: choose 720p or 1080p; 1080p rendering takes noticeably longer, so it is best run after the creative direction is confirmed.

Preset aspect ratios: aspect_ratio supports 16:9, 9:16, 1:1, and 21:9, so generation directly yields the target placement ratio without a second round of cropping.

Use Cases

• Vertical short videos for social media teams — use a one-sentence scene description plus a 9:16 aspect ratio to generate a roughly 15-second clip, ready for short-video platforms or feed placements.
• Early-stage pitches for advertising creatives — quickly produce multiple versions of a shot concept at 720p so clients can narrow down the direction at a low-cost stage.
• Storyboarding and narrative previews — turn storyboard text into dynamic clips with sound to explain camera movement and pacing to the production team.
• Widescreen-style content — choose the 21:9 aspect ratio to generate cinematic landscape clips for openings or brand image assets.

Limitations and Selection Advice

Currently only text input is supported; you cannot constrain the visuals with reference images or first/last frames, so projects demanding high character consistency and precise composition are hard to control accurately. Public information differs on the maximum resolution, and this route caps out at 1080p. 1080p rendering takes noticeably longer; for long-duration clips, test consistency and stability first. If you have a source image to use as a starting point, switch to the image-to-video route in the same series; if you only need quick drafts, consider the Flash version.