R2

R2 is Cloudflare’s object storage: buckets of arbitrarily large objects addressed by key, with an S3-compatible API. In alchemy an R2 bucket is a one-line resource, and Workers reach it through typed, access-scoped bindings.

Reach for R2 whenever you need to store files: uploads, build artifacts, media, backups, or document corpora for AI Search.

Create a bucket

src/bucket.ts

import * as Cloudflare from "alchemy/Cloudflare";

export const Bucket = Cloudflare.R2.Bucket("Bucket");

Yield it inside your Stack:

alchemy.run.ts

import * as Alchemy from "alchemy";
import * as Cloudflare from "alchemy/Cloudflare";
import * as Effect from "effect/Effect";
import { Bucket } from "./src/bucket.ts";

export default Alchemy.Stack(
  "MyApp",
  {
    providers: Cloudflare.providers(),
    state: Cloudflare.state(),
  },
  Effect.gen(function* () {
    const bucket = yield* Bucket;

    return { bucketName: bucket.bucketName };
  }),
);

No name required — alchemy generates a unique one from the app, stage, and logical ID.

Bind it to a Worker

Bind the bucket in the Worker’s init phase and use the typed client in the runtime handlers. This Worker stores objects on PUT /:key and serves them back on GET /:key:

src/worker.ts

import * as Cloudflare from "alchemy/Cloudflare";
import * as Effect from "effect/Effect";
import { HttpServerRequest } from "effect/unstable/http/HttpServerRequest";
import * as HttpServerResponse from "effect/unstable/http/HttpServerResponse";
import { Bucket } from "./bucket.ts";

export default Cloudflare.Worker(
  "Worker",
  { main: import.meta.url },
  Effect.gen(function* () {
    const bucket = yield* Cloudflare.R2.ReadWriteBucket(Bucket);

    return {
      fetch: Effect.gen(function* () {
        const request = yield* HttpServerRequest;
        const key = request.url.split("/").pop()!;

        if (request.method === "PUT") {
          yield* bucket.put(key, request.stream, {
            contentLength: Number(request.headers["content-length"] ?? 0),
          });
          return HttpServerResponse.empty({ status: 201 });
        }

        const object = yield* bucket.get(key);
        if (object === null) {
          return HttpServerResponse.text("Not found", { status: 404 });
        }
        return HttpServerResponse.text(yield* object.text());
      }).pipe(
        Effect.catchTag("R2Error", (error) =>
          Effect.succeed(
            HttpServerResponse.text(error.message, { status: 500 }),
          ),
        ),
      ),
    };
  }).pipe(Effect.provide(Cloudflare.R2.ReadWriteBucketBinding)),
);

R2 operations can fail with a typed R2Error — Effect keeps it in the type system until you handle it, here with Effect.catchTag. Tutorial part 2 builds this Worker step by step.

Read, Write, ReadWrite

The bucket capability is split by access level so each Worker gets least privilege:

• Cloudflare.R2.ReadBucket — head, get, list.
• Cloudflare.R2.WriteBucket — put, delete, multipart uploads.
• Cloudflare.R2.ReadWriteBucket — both.

Each level has two interchangeable implementations you provide as a layer on the Worker:

• *BucketBinding (ReadBucketBinding, WriteBucketBinding, ReadWriteBucketBinding) — a native R2 binding on the Worker, the default choice.
• *BucketHttp (ReadBucketHttp, WriteBucketHttp, ReadWriteBucketHttp) — the same client over Cloudflare’s HTTP API with a scoped API token, for when a native binding isn’t available.

Your runtime code depends only on the capability (ReadBucket(Bucket) etc.) — swapping the implementation layer doesn’t touch the handlers.

Where next

• Tutorial part 1 — deploy your first bucket.
• Add AI Search (AutoRAG) — RAG over documents stored in R2.

Related:

• Workers — how buckets get read and written.

Reference:

• Bucket API reference