Runway Gen-4 API: Pricing, Specs, and How to Access It
Runway Gen-4 turns an image into a 5–10s 720p video. What its API and plans cover, full specs, and the video APIs you can call today.
Runway Gen-4 is the AI video generator Runway released on March 31, 2025. Give it one input image and a text prompt and it returns a 5- or 10-second 720p video at 24fps, with the character and scene consistency that made it Runway's breakout model. It is no longer the newest model in the lineup (Gen-4.5 took that spot in December 2025), but Gen-4 Turbo is still the cheapest image-to-video model on Runway's API. This post covers what Gen-4 does, how Runway bills it, how to call the Runway API, and which comparable models you can call pay-per-use today.
TL;DR: Runway Gen-4 is image-to-video only: one input image plus a text prompt in, a 5- or 10-second 720p video at 24fps out. In Runway's app it is billed in credits that come with a monthly plan; on Runway's developer API you buy credits directly, and Gen-4 Turbo costs well under half as much per second as the newer Gen-4.5. Runway models are not available on Unifically. The closest live alternatives here are Veo 3.1, Kling 3.0, SeeDance 2.0, and Wan 2.6, all pay-per-use with no subscription.
What is Runway Gen-4?
Gen-4 launched on March 31, 2025 as Runway's flagship video model, with the faster Gen-4 Turbo following days later. Its selling point was consistency: keep the same character, object, or location across separate generations from a single reference image, with no fine-tuning. That solved the biggest complaint about AI video at the time, and it is why "runway gen 4" is still one of the most-searched video model names in 2026.
The model is strictly image-to-video. Every generation starts from a required input image that becomes the first frame, and the text prompt should describe the motion, not the scene. There is no text-to-video mode on Gen-4; that arrived with Gen-4.5.
| Spec | Gen-4 | Gen-4 Turbo |
|---|---|---|
| Input | Image (required) + text prompt | Image (required) + text prompt |
| Durations | 5 or 10 seconds | 5 or 10 seconds |
| Output resolution | 720p class | 720p class |
| Aspect ratios | 16:9 (1280×720), 9:16 (720×1280), 1:1 (960×960), 4:3 (1104×832), 3:4 (832×1104), 21:9 (1584×672) | Same six |
| Frame rate | 24fps | 24fps |
| Prompt limit | 1,000 characters | 1,000 characters |
A few things around the edges: outputs can be upscaled to 4K as a separate action in the app, a fixed seed setting reproduces similar motion across runs, and Gen-4 outputs video without sound. Audio is a separate tool in Runway's suite, not part of the generation.
The Gen-4 family also covers two related tools. Gen-4 References handles consistent characters and objects in image generation (the API model gen4_image takes reference images). Act-Two is performance capture: record yourself acting and drive a character with your movement and expression.
Is Gen-4 still Runway's latest model?
No. Runway announced Gen-4.5 on December 1, 2025, and its help center now files Gen-4 under "an older generation" of models. At launch, Gen-4.5 topped the crowd-voted Video Arena leaderboard, ahead of Google's Veo and OpenAI's Sora 2 Pro.
The practical differences, from Runway's own spec sheets:
- Gen-4.5 does text-to-video. No input image needed, 16:9 at 720p. Image-to-video works too, across the same six aspect ratios as Gen-4.
- Flexible durations. 2 to 10 seconds, against Gen-4's fixed 5 or 10.
- Same in-app price as base Gen-4. It costs the same credits per second, with a Standard plan or higher required in the app.
- Better motion and prompt following. Gen-4.5 handles sequenced instructions in one prompt: camera choreography, timed events, atmosphere changes.
So why would anyone still use Gen-4? One reason: Gen-4 Turbo costs well under half as many credits per second as Gen-4.5, and it is still the model Runway recommends for testing ideas before spending on a final pass. For video-to-video editing, Runway's current answer is Aleph 2.0.
Runway Gen-4 pricing: credits and plans
Runway bills everything in credits. In the app, credits come bundled with a subscription. On the developer API, you buy them directly at a flat rate per credit.
The app plans are Free (a one-time credit grant), Standard, Pro, Max, and Enterprise; current prices and monthly credit allowances are on runway.com/pricing. Max replaced the old Unlimited plan, which Runway now labels legacy. Extra credits can be bought on any paid plan, and they do not expire.
Per second, base Gen-4 and Gen-4.5 cost the same number of credits, and Gen-4 Turbo costs well under half of that. Base Gen-4 is app-only; on the API you get Gen-4 Turbo and Gen-4.5. Because a plan's credits are spent per second of output, a ten-second video costs twice a five-second one on every model.
Does Runway have an API?
Yes. The developer platform lives at dev.runwayml.com, with docs at docs.dev.runwayml.com. It runs on its own credit purchases; no subscription needed. Note that base Gen-4 is app-only. On the API, the Gen-4 route is gen4_turbo.
Runway's own models on the API:
| API model | Task | Billed |
|---|---|---|
gen4_turbo | Image-to-video | Per second |
gen4.5 | Text- and image-to-video | Per second |
act_two | Performance capture | Per second |
aleph2 | Video-to-video editing | Per second |
gen4_image | Image generation with references | Per image, by resolution |
gen4_image_turbo | Fast image generation | Per image |
The same API also carries third-party models under Runway's credit system (Veo 3.1, SeeDance 2, Hailuo 3, ElevenLabs audio, and others), at higher per-second rates than Runway's own models.
Official SDKs are @runwayml/sdk for Node and runwayml for Python. A Gen-4 Turbo call looks like this:
from runwayml import RunwayML
client = RunwayML() # reads RUNWAYML_API_SECRET
task = client.image_to_video.create(
model="gen4_turbo",
prompt_image="https://example.com/first-frame.jpg",
prompt_text="Slow dolly-in as the subject turns toward the window",
ratio="1280:720",
duration=5,
).wait_for_task_output()
print(task.output)
Generation is asynchronous: the API returns a task, and the SDK helper polls until the video is ready. API keys are issued in the developer portal after sign-up.
Runway Gen-4 vs alternatives you can call today
Runway's models are not available on Unifically, and we are not going to pretend otherwise. To call Gen-4 or Gen-4.5, go through Runway's own API or app as described above.
If what you want is strong image-to-video billed pay-per-use, with no subscription and no credit packs, these are the closest models live on Unifically today:
- Veo 3.1: up to 8 seconds, 720p to 4K, with synchronized dialogue, ambient sound, and effects generated in the same call. From $0.075 per video. Gen-4 outputs silent video, so native audio is the clearest capability gap.
- Kling 3.0: multi-shot generation with 2 to 6 scenes per call, 3 to 15 seconds single-shot, a 4K mode, and lip-sync. From $0.06 per second.
- SeeDance 2.0: up to 9 image, video, and audio references against Gen-4's single input image, 4 to 15 seconds, up to 4K on Pro. The Mini variant starts at $0.044 per second.
- Wan 2.6: text-, image-, or reference-to-video with up to 5 references, 720p or 1080p, 2 to 15 seconds, with automatic audio. The Flash variant starts at $0.0175 per second at 720p.
All four run through one API key with pay-per-use billing and no monthly fee. New accounts start with a $0.50 balance; on video models that covers only a few seconds, so treat it as a smoke test rather than a trial. Live rates for every model are on the pricing page, and the full catalog is at /models.
Frequently asked questions
How much does Runway Gen-4 cost?
Runway bills Gen-4 in credits per second of output, and Gen-4 Turbo costs well under half as many credits as base Gen-4. In the app, credits come with a monthly plan; on Runway's API you buy them directly, and only Gen-4 Turbo is available there. Runway lists current plan and credit prices at runway.com/pricing.
Is Runway Gen-4 free?
Partly. Runway's Free plan includes a one-time credit grant, enough for a handful of short Gen-4 Turbo videos, and it does not refill monthly. After that you need a paid plan or API credits.
What is the difference between Gen-4 and Gen-4 Turbo?
Same task, same specs. Turbo generates faster and costs well under half as many credits per second as Gen-4. Runway recommends drafting in Turbo and switching to Gen-4 only when Turbo's results fall short. The API offers only the Turbo version, as gen4_turbo.
Does Runway Gen-4 do text-to-video?
No. Gen-4 and Gen-4 Turbo require an input image that becomes the first frame; the prompt describes the motion. For text-to-video from Runway, use Gen-4.5, which generates 16:9 720p video from a prompt alone.
What resolution is Runway Gen-4?
720p class, in six aspect ratios: 1280×720, 720×1280, 960×960, 1104×832, 832×1104, and 1584×672, all at 24fps. The app can upscale a finished video to 4K as a separate step.
Can I use the Runway API without a subscription?
Yes. The developer API at dev.runwayml.com bills its own credits, bought directly, with no plan required. Subscriptions only cover the app at runway.com.
We will update this post when Runway changes API credit rates, when Gen-4.5's promised additional input types arrive, or if Gen-4 Turbo leaves the API. If Runway models ever come to Unifically, this comparison section is where we will say so.
