Send files securely from your app or AI agent
Deliver a file to a person as a one-time, encrypted, auto-deleting download link, over a REST API and an MCP server. UK-hosted, with an audit trail and a zero-knowledge option.
What the Secure Send API does
AI agents and backends increasingly produce sensitive files: contracts, KYC extracts, medical letters, financial summaries. Dropping them into chat or a plain email is not safe, and a raw presigned URL has no expiry, no one-time access and no audit. FileSeal gives you a compliant secure-egress channel in one request.
Encrypted
AES-GCM-256. A one-click zero-knowledge mode keeps the key out of FileSeal entirely.
One-time + expiring
The link opens once, then the file is permanently deleted. Set an expiry from 1 to 168 hours.
Audited + UK-hosted
Every send and collection is logged. Hosted in the UK (London), GDPR-ready.
MCP-native
Agents call it as a tool via the fileseal-send MCP server. No glue code.
Send a file in one request
Encrypt the file on your side, then create the send. In link mode you relay the returned#k= link to the recipient and FileSeal never receives the key.
REST
curl -X POST https://fileseal.uk/v1/sends \
-H "Authorization: Bearer $FILESEAL_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"deliveryMode": "link",
"files": [{
"filename": "contract.pdf",
"mimeType": "application/pdf",
"ciphertextBase64": "<AES-GCM ciphertext, base64>"
}]
}'MCP server (.mcp.json)
{
"mcpServers": {
"fileseal-send": {
"command": "node",
"args": ["mcp/fileseal-send/index.mjs"],
"env": {
"FILESEAL_API_KEY": "${FILESEAL_API_KEY}",
"FILESEAL_API_BASE_URL": "https://fileseal.uk"
}
}
}
}Then your agent calls the secure_send tool; it encrypts locally and returns the share link.
Encryption and the zero-knowledge option
Default: link / zero-knowledge (most private)
The AES key lives only in the link’s #k=fragment, which browsers never send to the server, so FileSeal stores ciphertext it cannot read. You relay the link to the recipient.
Opt-in: email delivery
Pass deliveryMode: "email" and FileSeal holds the key so it can email the recipient a working one-time link. Encrypted and safe from outsiders, not zero-knowledge from FileSeal.
Start sending in minutes
Create an account, generate an API key in Settings, and make your first secure send. Free to evaluate.