Generate 3–20 second 720p clips with Kling 4.0 Flash (Kling 4 Flash) through EvoLink's unified API. Choose text, a first frame, reference images and videos, or video editing, then check the model ID and billed duration for your route.
Choose a Kling 4.0 Flash route and check its estimated cost before generating with your EvoLink balance. The playground uses the same endpoint and billing rules as your API integration.
Create a video
Runs against the live API with your own balanceWrite a prompt, add the first frame, references, or source video your route needs, then hit Generate — your result will appear here.
Results are kept for 24 hours — download anything you want to keep.
Kling 4.0 Flash bills per second of 720p output video. When a reference-to-video request includes reference video, billed seconds are the output plus the longer of the reference video total or the output, at a lower per-second rate. Video edit bills the output plus the longer of the source video or the output at the video-edit rate, which is twice the source length with the default auto duration. First frames and reference images are free.
Your first test
Text-to-video, 3s at 720P — the cheapest possible request, no reference video3 seconds at 720P
About 33 runs for $10
Credits are reserved when the task is created and settled when it finishes. Failed tasks are refunded in full.
Top up
At the first-test settings: 3s at 720PEnough to validate the four routes end to end
Enough for a full round of creative iteration
Enough to run a small production batch
Calculated with the same function the Playground uses, at the rate for your user group. With reference video, an 8s reference and a 5s output bill as 13 seconds at the video-input rate. A video edit of a 5s clip with duration auto bills as 10 seconds at the video-edit rate.
| Route | 720P | Billed seconds |
|---|---|---|
| Text-to-videokling-v4-flash-text-to-video | $0.094/s 6.392 cr/s | Output seconds |
| Image-to-videokling-v4-flash-image-to-video | $0.094/s 6.392 cr/s | Output seconds |
| Reference-to-videoWith reference images only | $0.094/s 6.392 cr/s | Output seconds |
| Reference-to-videoWith reference video | $0.063/s 4.284 cr/s | Output + max(reference video, output) |
| Video editkling-v4-flash-video-edit | $0.063/s 4.284 cr/s | Output + max(source video, output) |
First frames and reference images are never billed. The reference-video row has a lower per-second rate, but billed seconds include the reference video, so a request with video input usually costs more in total. Video edit bills the output plus the longer of the source video or the output; with the default auto duration a 5s clip costs 10 billed seconds.
The minimum charge is 3s at 720P, which is also the cheapest request you can send.
Kling 4.0 Flash is the short-clip tier of Kuaishou's Kling 4.0 family. EvoLink exposes four model IDs on one endpoint: text-to-video, image-to-video from a first frame, reference-to-video with up to 10 images and 5 videos, and video edit for an existing clip. Clips run 3–20 seconds at 720p.
Pick the model ID that matches your input. Each route accepts only its own media fields.
kling-v4-flash-text-to-videoGenerate 720p video from a text prompt, 3-20 seconds.
kling-v4-flash-image-to-videoAnimate a first frame into a 720p clip of 3-20 seconds.
kling-v4-flash-reference-to-videoGuide the video with up to 10 reference images and 5 reference videos.
kling-v4-flash-video-editEdit one source video with a prompt and optional reference images; framing follows the source and length defaults to it.
The fields that decide how you call it, and what each one means for your integration.
kling-v4-flash-text-to-video / kling-v4-flash-image-to-video / kling-v4-flash-reference-to-video / kling-v4-flash-video-edit
Each route accepts only its own media: no media on text-to-video, a first frame on image-to-video, reference images and videos on reference-to-video, and one source video plus reference images on video edit. Sending another route's fields returns 400.
720p
Every request is generated and billed at 720p, with or without the quality field. Use Kling 4.0 when you need 1080p.
3-20 seconds, integer
One request produces a clip of up to 20 seconds; it does not guarantee an uninterrupted take. Billing follows the requested duration. Video edit also accepts auto (the default), which matches the source video’s length.
Up to 10 images and 5 videos
Reference videos are 3-20s each and 20s in total. The prompt addresses them as <<<image_1>>> and <<<video_1>>>, numbered independently in array order.
16:9 / 9:16 / 1:1 / 21:9
Available on text-to-video and reference-to-video. Image-to-video follows the first frame and video edit follows the source video; neither takes aspect_ratio.
First frame only
Image-to-video takes image_start only; image_end and keyframes return 400. Use Kling 4.0 image-to-video for first-to-last frame or keyframe control.
One source video, 3-20s
The output keeps the source aspect ratio and original audio, so aspect_ratio is not accepted. duration is auto by default (same length as the source) or 3-20 seconds. Billed seconds are the output plus the longer of the source or the output, so auto bills twice the source length.
These fields cover the main integration decisions. Open the API Reference for route-specific request and response examples.
modelstringChoose the text, image, reference, or edit model ID that matches your input.
Default: route-specific
promptstringDescribe the scene, motion, and camera. Up to 2500 characters; reference assets are addressed as <<<image_1>>> and <<<video_1>>>.
Default: required
qualityenum720p is the only option. Omitting it gives the same result.
Default: 720p
durationintegerSet 3-20 output seconds. Video edit also takes auto (the default) to match the source length.
Default: 5
aspect_ratioenumUse 16:9, 9:16, 1:1, or 21:9 on text and reference routes.
Default: 16:9
image_startstringFirst frame for image-to-video. Last and middle frames are not accepted on Flash.
Default: image route
image_urlsarrayUp to 10 reference images, addressed as <<<image_1>>>, <<<image_2>>>… in array order. Not billed.
Default: reference / edit routes
video_urlsarrayReference route: up to 5 reference videos, 20s in total. Edit route: exactly one source video, 3-20s. Their seconds are billed together with the output.
Default: reference / edit routes
Use the EvoLink API for product integration and batch jobs, or call it from Codex, Claude, or Gemini for fast creative and development workflows. Both paths share the same EvoLink API key, balance, model routes, and task history.
Best for: product backends, batch jobs, automated workflows
Call EvoLink’s unified video API from your server and control the model ID, parameters, task queue, callbacks, and result storage.
Best for: creative and development tasks in Codex, Claude, and Gemini
Give the Agent your output goal, assets, and acceptance criteria. It can choose the route, assemble the request, track the task, and return the result without requiring you to hand-code every step.
Use Kling 4.0 Flash to test short video ideas when 720p meets your delivery requirements.
This example shows the shortest runnable flow: create a task, save the returned task ID, then poll or wait for an HTTPS callback. Open the API tab for the complete parameter and response reference.
curl -X POST https://api.evolink.ai/v1/videos/generations \
-H "Authorization: Bearer $EVOLINK_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "kling-v4-flash-text-to-video",
"prompt": "A paper boat drifts down a rain-soaked street at dusk, neon reflections ripple, slow tracking shot",
"duration": 5,
"quality": "720p",
"aspect_ratio": "16:9",
"callback_url": "https://your-domain.com/webhooks/video-task-completed"
}'
# Save the returned task ID, then query:
curl https://api.evolink.ai/v1/tasks/{task_id} \
-H "Authorization: Bearer $EVOLINK_API_KEY"Check every value against the parameter cards above: ranges, allowed options, asset counts, and file types must match the selected route.
Check the Authorization bearer token and confirm the available balance and task billing in the console.
Review likeness rights, brand assets, readable text, sensitive content, and input-asset compliance.
A Kling 4.0 Flash task that reaches a final failed state is not charged. Keep the task ID, inspect the final state, and identify whether the cause is validation, review, or execution before retrying.
callback_url must be a public HTTPS URL, not localhost or a private network address. Always keep the task ID as a polling fallback.
Choose Kling 4.0 Flash for short 720p clips, high-volume drafts, and quick edits. Move to Kling 4.0 when a shot needs 1080p, a longer take, or frame-by-frame control.
Generation is asynchronous. Design around completion events and promote the drafts you keep to a final route.
Return the task ID immediately, show a pending state, and finish through polling or an HTTPS callback.
Budget for creative retries as well as video seconds: a completed clip may still fail your review. Reference-video seconds are billed too; trim inputs to the part that matters.
Store the files you want to keep as part of your completion handler instead of relying on result links.
Images and videos are numbered independently and follow array order. Reordering an array changes what <<<image_2>>> refers to.
With reference video, billed seconds are the output plus the longer of the reference total or the output. A 10s output with 5s of reference video bills as 20 seconds; with 15s of reference video, it bills as 25 seconds. Both use the video-input rate.
image_end, keyframes, 1080p, negative_prompt, sound, watermark settings, saved subjects, and multi-shot storyboards (model_params) are not accepted on Kling 4.0 Flash routes and return 400.
Billed per second of video, with a separate rate when video input is included. Your exact rate is in the table above.
Reuse your EvoLink API key and the shared video generation endpoint, without a separate Kling developer account.
Use one prepaid balance for Kling 4.0 Flash and other EvoLink models, without buying separate vendor credits.
Poll a single task endpoint or register a callback. Reserved and settled amounts are both visible in your logs.
Keep the same EvoLink API key, video generation endpoint, and task tracking flow when switching models. Check the new model’s accepted fields, duration limits, and pricing, then test its output before changing production traffic.
Compare Kling generations under one EvoLink account and API key, then choose by resolution, length, editing features, and cost.
Kling 4.0
The full Kling 4.0 model: 1080p, takes of up to 30 seconds, and first, middle, and last frame control.
View
Kling 3.0 Motion Control
The previous generation's motion control route: copy a reference video's motion onto a character image.
View
Seedance 2.5
ByteDance's video model with multi-shot storytelling and image, video, and audio references.
View
Veo 3.1
Google DeepMind's Veo 3.1: 8-second clips with native audio, available in Fast and Pro variants.
ViewWhere to go once you have decided Kling 4.0 Flash fits.
Per-second rates for every video model in one table.
One key works across every model on the platform.
1080p, 30-second takes, and keyframe control on the full model.
Kling 4.0 Flash is the 720p short-clip tier of Kuaishou's Kling 4.0 family. EvoLink provides kling-v4-flash-text-to-video, kling-v4-flash-image-to-video, kling-v4-flash-reference-to-video, and kling-v4-flash-video-edit through /v1/videos/generations.
Flash outputs 720p only, runs 3 to 20 seconds per request, and takes a first frame only on image-to-video. Kling 4.0 adds 1080p, takes of up to 30 seconds, and first, middle, and last frame control. Both use the same endpoint and request format, and Flash costs less per second.
Each route accepts different media: none on text-to-video, a first frame on image-to-video, reference images and videos on reference-to-video, and one source video on video edit. Choose the ID that matches your input; media fields from another route return 400.
Total cost depends on output duration and any input video. Without video input, only output seconds are billed. With reference video, billed seconds are the output plus the longer of the reference total or the output, at the video-input rate. A lower per-second rate does not necessarily mean a cheaper task. Video edit bills the output plus the longer of the source or the output; auto bills twice the source length. See the table above for current rates.
720p only. You can omit quality or send 720p; any other value returns 400. Use Kling 4.0 when you need 1080p.
3 to 20 seconds per request, in whole seconds. Video edit defaults to the length of its source video (duration auto) or takes 3 to 20 seconds.
No. Flash image-to-video takes image_start only; image_end and keyframes return 400. Use Kling 4.0 image-to-video when you need a first-to-last frame transition or middle frames.
Write <<<image_1>>> for the first image in image_urls and <<<video_1>>> for the first video in video_urls. Images and videos are numbered independently and follow array order.
There is no separate input charge for first frames or reference images. Video generation is still billed; reference videos and source videos also affect the billed duration.
On the output plus the longer of the source video or the output, at the video-edit rate; the source length is rounded up to a whole second. With the default duration auto the output matches the source, so a 5s clip bills as 10 seconds; a 10s clip with duration 20 bills as 40 seconds. Reference images are free.
These routes do not accept structured multi-shot storyboards through model_params. A prompt can describe scene changes, and a generated clip may contain cuts; a single uninterrupted take is not guaranteed. For precise editing, generate shots separately and review the results.
Not in this release. Saved subjects (element_list), custom voices, and video extension are not available on these routes yet.
No. Use the EvoLink API reference for each route. These routes accept 720p output and prompts up to 2500 characters. 4K, HDR controls, saved subjects, custom voices, multi-shot storyboards and video extension are not offered here. A provider announcement or client subscription does not define EvoLink's request fields.
Use an EvoLink account, API key, and sufficient EvoLink balance. A Kling app subscription is not required for these EvoLink routes, and Kling app credits do not pay for EvoLink API requests. Check the pricing section before submitting a task.
Kling positions Flash for faster creation, but that is not a fixed API completion-time guarantee. Queue time, input media, output duration, and retries affect your workflow. Compare completion time and cost per accepted clip using your own prompts and inputs.