Replicate Free code examples in Python and JavaScript

Same package name as Python. The constructor reads REPLICATE_API_TOKEN, so nothing about the token appears in code.

npm install replicate

export REPLICATE_API_TOKEN="r8_your-token"

A model reference can be owner/name, or owner/name:version pinned to an exact build. PIN IT IN PRODUCTION — an unpinned reference follows the model's latest version, and community models change without warning.

import { writeFile } from "node:fs/promises";
import Replicate from "replicate";

const replicate = new Replicate();

const [output] = await replicate.run(
  "black-forest-labs/flux-schnell",
  { input: { prompt: "astronaut riding a rocket like a horse" } },
);

// FileOutput is a ReadableStream; writeFile accepts it directly.
await writeFile("output.png", output);

The client, the auth and the output handling stay put. Only the reference and the input keys change — which is the whole argument for routing through Replicate rather than integrating four vendors.

const JOBS = [
  ["black-forest-labs/flux-schnell",
   { prompt: "a brass microphone on a dark desk" }],

  ["stability-ai/sdxl",
   { prompt: "a brass microphone on a dark desk", width: 1024 }],
];

for (const [reference, input] of JOBS) {
  const result = await replicate.run(reference, { input });

  // Some models return an array, some a single FileOutput.
  const files = Array.isArray(result) ? result : [result];

  await Promise.all(
    files.map((file, index) =>
      writeFile(`${reference.replace("/", "-")}-${index}.png`, file),
    ),
  );
}

run() waits for the whole prediction, which for a video model is minutes. predictions.create returns straight away and posts to your webhook when it completes.

const prediction = await replicate.predictions.create({
  model: "black-forest-labs/flux-schnell",
  input: { prompt: "painting of a cat by andy warhol" },
  webhook: "https://my.app/webhooks/replicate",
  webhook_events_filter: ["completed"],
});

console.log(prediction.id, prediction.status);

The body is the full prediction. Check status before reading output — a failed prediction has an error and no output, and a webhook fires for both.

import express from "express";

const app = express();
app.use(express.json());

app.post("/webhooks/replicate", async (request, response) => {
  const { id, status, output, error } = request.body;

  if (status !== "succeeded") {
    console.error(`prediction ${id} ${status}: ${error ?? "no detail"}`);
    return response.sendStatus(204);
  }

  // output here is plain URLs, not FileOutput — this is a fresh
  // HTTP request, not the SDK. Download them before they expire.
  const urls = Array.isArray(output) ? output : [output];
  for (const [index, url] of urls.entries()) {
    const file = await fetch(url);
    await writeFile(`${id}-${index}.png`,
      Buffer.from(await file.arrayBuffer()));
  }

  response.sendStatus(200);
});

app.listen(3000);