UploadToBlockchain proves a file existed on a given date — no account, pay per upload. Your file is hashed (optionally encrypted client-side with AES-256-GCM, so even we can't read it) and stored permanently on Arweave, giving you a public, verifiable record. Add a Bitcoin-backed certificate via OpenTimestamps — it only ever sees the hash, never the file. Built for creators and freelancers who need solid proof of prior existence. $4.99 per proof, $9.99 with Bitcoin. Up to 50MB.