transfr.one worker

A Cloudflare Worker for dead-simple, temporary file transfer: PUT a file, get back a URL with an unguessable key, and the file is gone after 24 hours. Files are stored in R2 and can be encrypted end-to-end in the browser (OpenPGP) before they ever leave the machine.

Check it out: https://transfr.one

API

Method	Path	Description
GET	/	The landing page with usage instructions.
PUT/POST	/<name>	Upload a file, returns the URL to download it from.
GET/HEAD	/<key>	Download a file. Browsers get an HTML page instead; ?raw always returns the bytes.
OPTIONS	any	CORS preflight.

curl --upload-file ./file.txt https://transfr.one/file.txt
# https://transfr.one/68d0f3a2-3f1c9b27d4e0/file.txt

curl -L https://transfr.one/68d0f3a2-3f1c9b27d4e0/file.txt > file.txt

Encrypt before uploading to keep the contents private from the server:

gpg -c -o- file.txt | curl https://transfr.one/file.txt.pgp --data-binary @-

Object keys are <expiry-hex>-<random-hex>/<file name>. The expiry is part of the key, so the worker stops serving a file on time even though R2 lifecycle rules only delete once a day; the 6 random bytes are the only secret protecting a file, so treat the URL like a password.

Uploads are served back with Content-Disposition: attachment and X-Content-Type-Options: nosniff unless they are a type the browser can safely render in place (images other than SVG, video, audio, text/plain), so an uploaded HTML file cannot run script on the worker's origin.

Layout

html/            the two pages, as plain HTML with {{TOKEN}} placeholders
  index.html       landing page: drag & drop upload, optional PGP encryption
  access.html      what a browser sees for an uploaded file, with PGP decryption
src/
  index.ts         entry point and routing
  upload.ts        PUT/POST: validation and storing the object
  download.ts      GET/HEAD: ranges, conditional requests, download headers
  pages.ts         fills the HTML templates
  templates.ts     single pass {{TOKEN}} substitution
  escape.ts        HTML and JSON-in-script escaping
  keys.ts          key generation, expiry parsing
  config.ts        bindings and variables, validated
  cors.ts          CORS headers and preflight
  http.ts          response helpers and page security headers
  mime.ts          content type validation, Content-Disposition
  format.ts        human readable sizes and durations
test/            vitest tests, run inside workerd via @cloudflare/vitest-pool-workers

The HTML files are bundled as text modules (the Text rule in wrangler.toml), so they are plain editable HTML rather than strings inside TypeScript.

Development

npm install
npm run dev        # wrangler dev, R2 simulated locally
npm test           # vitest, runs the worker inside workerd
npm run typecheck

Initial setup

Install wrangler and log in with wrangler login.

1. Create the bucket and have R2 clean up after itself:

   wrangler r2 bucket create transfr-temp-store
   wrangler r2 bucket lifecycle add transfr-temp-store expire-1-day "" --expire-days 1

2. Point wrangler.toml at it: set bucket_name under [[r2_buckets]], and make sure binding matches the R2_DEFAULT_NAMESPACE variable.

3. Deploy and map the route to your domain on the Cloudflare dashboard:

   npm run deploy

Configuration

Variables in wrangler.toml under [vars]:

Variable	Default	Description
R2_DEFAULT_NAMESPACE	–	Name of the R2 binding to store files in (required).
R2_MAX_FILE_SIZE_BYTES	21000000	Largest accepted upload.
R2_DEFAULT_FILE_TTL	86400	File lifetime in seconds.
RAW_ONLY_HOSTS	–	Hosts that always serve bytes, never the HTML page, e.g. for embedding.

An invalid value is a startup error rather than a silently ignored limit.