Developer API

Authentication

Create an API key under Account → API keys, then send it as a bearer token:

curl -H "Authorization: Bearer ufax_YOUR_KEY" \
  https://unlimitedfaxing.com/api/v1/documents

Templates

Templates use {{Placeholder}} tokens and a simple markup subset (# headings, - bullets, | pipe | tables, **bold**).

# Create a template
curl -X POST -H "Authorization: Bearer ufax_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{"name":"Invoice","body":"# Invoice\n\nBill to: {{Client}}\n\n**Total: {{Total}}**"}' \
  https://unlimitedfaxing.com/api/v1/templates

# List templates
curl -H "Authorization: Bearer ufax_YOUR_KEY" \
  https://unlimitedfaxing.com/api/v1/templates

Documents

Generate a PDF from a template plus data. Consumes 1 document from your monthly quota.

# Generate a PDF
curl -X POST -H "Authorization: Bearer ufax_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{"templateId":1,"data":{"Client":"Acme Corp","Total":"$500.00"}}' \
  https://unlimitedfaxing.com/api/v1/documents
# → {"id":"…","fileName":"Invoice-20260907-120000.pdf","pages":1,"downloadUrl":"/api/v1/documents/…/file"}

# Download it
curl -H "Authorization: Bearer ufax_YOUR_KEY" \
  https://unlimitedfaxing.com/api/v1/documents/{id}/file -o invoice.pdf

Fax

Send a PDF or TIFF. Consumes fax pages from your quota ($0.03/page overage on paid plans).

# Send a fax
curl -X POST -H "Authorization: Bearer ufax_YOUR_KEY" \
  -F "file=@contract.pdf" -F "destination=+14155551212" \
  https://unlimitedfaxing.com/api/v1/fax
# → {"id":"…","status":"Sending","pages":3}

# Check status
curl -H "Authorization: Bearer ufax_YOUR_KEY" \
  https://unlimitedfaxing.com/api/v1/fax/{id}

Sign

Request e-signatures. Signers get a link (no account needed). When everyone signs, the final PDF includes an audit certificate. Consumes 1 signature per signer.

# Create a signature request (upload a PDF…)
curl -X POST -H "Authorization: Bearer ufax_YOUR_KEY" \
  -F "file=@contract.pdf" -F "title=MSA" \
  -F 'signers=[{"email":"jane@example.com","name":"Jane Doe"}]' \
  https://unlimitedfaxing.com/api/v1/sign

# …or reference a generated document
curl -X POST -H "Authorization: Bearer ufax_YOUR_KEY" \
  -F "documentId=GUID" -F "title=MSA" \
  -F 'signers=[{"email":"jane@example.com"}]' \
  https://unlimitedfaxing.com/api/v1/sign

# Poll status; finalDownloadUrl appears when completed
curl -H "Authorization: Bearer ufax_YOUR_KEY" \
  https://unlimitedfaxing.com/api/v1/sign/{id}

Webhooks

Register endpoints under Account → Webhooks. We POST JSON with an X-Ufx-Signature header — HMAC-SHA256 of the raw request body using your endpoint's signing secret:

{
  "id": "…",
  "type": "fax.status",
  "occurredAt": "2026-09-07T12:00:00Z",
  "data": { "id": "…", "status": "Delivered", "pages": 3 }
}

Event	Fired when
fax.status	An outbound fax changes status
fax.received	An inbound fax arrives
sign.completed	All signers have signed a request
document.generated	A document is generated via the API

Failed deliveries retry up to 3 times with backoff.

Errors & quotas

Errors return JSON with an error code. Exceeding your plan quota returns HTTP 402 with {"error":"quota_exceeded","remaining":…,"limit":…}. Free tier: 50 documents, 5 signatures, 10 fax pages per month.