Kling AI API vs Runway API

Kling AI API

Kling 3.0 from $0.084 a second, with audio from $0.126. Developer docs, API terms and pricing render only with JavaScript.

Runway API

OpenAPI 3.1, llms.txt and Markdown copies of every docs page. Gen-3 Alpha Turbo and Gen-4 Aleph were removed on 2026-07-30 with no prior notice in the changelog.

Kling AI API

1. Sign a JWT (HS256) with iss set to your AccessKey and a 30 minute exp, then send it as a bearer token
2. Generate a new key pair if you need Kling 3.0 Turbo. Older keys don't reach it
3. Create with POST /v1/videos/text2video or /v1/videos/image2video, then poll the task id until it succeeds
4. Take model IDs and prices from kling.ai/llms.txt. The HTML docs need JavaScript
5. Email support@kling.ai to revoke training use of your Input. The terms don't exempt API calls

Runway API

1. Send X-Runway-Version: 2024-11-06 on every request or it fails
2. Use the SDK's wait-for-output helper or poll GET /v1/tasks/{id} until SUCCEEDED or FAILED
3. Don't retry a SAFETY.* failure unchanged. It's moderation, not an outage
4. Take model IDs from the models page, not memory. Two were removed without notice on 2026-07-30
5. Copy outputs to your own storage. URLs expire within 24 to 48 hours