Kling 4.0 Image to Video API

Klingvideo$0.166 / second

Submit a Kling 4.0 Image to Video run over HTTP, then poll it or take a webhook. Results are files on media.ezflows.io. Try it in the playground first.

Async: the POST answers at once with a request id. Poll it, or take the webhook.

Docs

Submit

Parameters at the top level of the JSON body. Answers 202 with a request id.

curlPOST /v1/models/kling-4-image-to-video

curl -X POST https://api.ezflows.io/v1/models/kling-4-image-to-video \
  -H "Authorization: Bearer $EZFLOWS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "first_frame_image": "https://media.ezflows.io/inputs/<account>/<upload-id>.png",
    "prompt": "The camera slowly orbits as the subject turns toward it and smiles, gentle breeze, warm natural light, soft ambient sound.",
    "duration": 5,
    "resolution": "1080p"
  }'

# 202 Accepted, at once — it never waits for the model:
# {"request_id": "req_8f2a41c9b70e4d15", "status": "queued",
#  "poll_url": "https://api.ezflows.io/v1/requests/req_8f2a41c9b70e4d15"}

Poll

Same bearer header, every few seconds, until the status is final.

curlGET /v1/requests/:id

REQUEST_ID=req_8f2a41c9b70e4d15   # from the POST

while :; do
  BODY=$(curl -s https://api.ezflows.io/v1/requests/$REQUEST_ID \
    -H "Authorization: Bearer $EZFLOWS_API_KEY")
  STATUS=$(echo "$BODY" | jq -r .data.status)
  case "$STATUS" in succeeded|failed|cancelled) break ;; esac
  sleep 3
done

echo "$BODY" | jq -r '.data.output.artifacts[].url'   # media.ezflows.io, kept 90 days

Response

Files are on media.ezflows.io, kept 90 days. A failed run says why and costs nothing.

json200 · succeeded

{
  "data": {
    "id": "req_8f2a41c9b70e4d15",
    "model_slug": "kling-4-image-to-video",
    "status": "succeeded",
    "http_status": 200,
    "cost": 0.83069,
    "auth_method": "api_key",
    "error": null,
    "submitted_at": "2026-09-12T18:07:21.114Z",
    "queue_started_at": "2026-09-12T18:07:21.402Z",
    "execution_started_at": "2026-09-12T18:07:22.010Z",
    "first_byte_at": "2026-09-12T18:07:52.871Z",
    "finished_at": "2026-09-12T18:07:55.203Z",
    "io_deleted_at": null,
    "canvas_id": null,
    "canvas_node_id": null,
    "client_attempt_id": null,
    "idempotency_key": null,
    "input": {
      "first_frame_image": "https://media.ezflows.io/inputs/<account>/<upload-id>.png",
      "prompt": "The camera slowly orbits as the subject turns toward it and smiles, gentle breeze, warm natural light, soft ambient sound.",
      "duration": 5,
      "resolution": "1080p"
    },
    "output": {
      "artifacts": [
        {
          "index": 0,
          "kind": "video",
          "contentType": "video/mp4",
          "url": "https://media.ezflows.io/outputs/<account>/req_8f2a41c9b70e4d15/0.mp4"
        }
      ]
    }
  }
}

Webhook

Skip polling: we POST the result to your endpoint, at least once.

Register: Create an endpoint under Webhooks in the dashboard; the signing secret is shown once.
Events: request.succeeded · request.failed · request.cancelled
Headers: ezflows-event-id (dedupe on it) · ezflows-timestamp (unix seconds) · ezflows-signature t=<ts>,v1=<hex HMAC-SHA256 of "<ts>.<raw body>">
Verify: Over the exact bytes received, in constant time; reject anything older than five minutes.
Respond: Any 2xx within 10 s. Redirects are not followed.
Retries: Five, with backoff: 30 s · 60 s · 2 min · 4 min · 8 min. Disabled after five consecutive dead deliveries.

jsonDelivery body

{
  "id": "82cf46a4-841e-41d6-b3c7-facc937d3252",
  "type": "request.succeeded",
  "created_at": "2026-09-12T18:07:55Z",
  "data": {
    "id": "req_8f2a41c9b70e4d15",
    "model_slug": "kling-4-image-to-video",
    "status": "succeeded",
    "cost": 0.83069,
    "output": {
      "artifacts": [
        {
          "url": "https://media.ezflows.io/…/0.mp4"
        }
      ]
    }
  }
}

curlverify.sh

# Create the endpoint under Webhooks in the dashboard; the signing secret is shown once.
# ezflows-signature: t=<ts>,v1=<hex HMAC-SHA256 of "<ts>.<raw body>">
# body.json = the exact bytes received. Reject anything older than five minutes.
EXPECTED=$({ printf '%s.' "$TS"; cat body.json; } \
  | openssl dgst -sha256 -hmac "$EZFLOWS_WEBHOOK_SECRET" -r | cut -d' ' -f1)

[ "$EXPECTED" = "$V1" ] && echo "valid" || echo "reject"

Parameters 5

Name	Type	Default	Allowed	Description
first_frame_imagerequired	string	—	one image url	Required starting image (JPG/PNG, min 300x300 px, up to 30 MB). Use a sharp frame whose subject can clearly move.
prompt	string	The camera slowly orbits as the subject turns toward it and smiles, gentle breeze, warm natural light, soft ambient sound.	—	Optional text directing the motion, camera and sound. Describe what moves, not the image already shown.
last_frame_image	string	—	one image url	Optional end image; Kling animates between the two frames. Add it to define a clear transition.
duration	integer	5	3–30	Output length in seconds (3-30). Use 5-10s for most clips; go longer only for sustained action.
resolution	enum	1080p	720p · 1080p	Output resolution, 720p or 1080p. Choose 1080p for final hero clips, 720p for faster drafts.

File inputs (first_frame_image: one image url · last_frame_image: one image url) take URLs. Upload the raw file to POST /v1/uploads with its own Content-Type and pass the url it returns. Inputs are kept 90 days.

Submit

Poll

Response

Webhook

Parameters 5

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