A whole subsystem
Documents, fields, signing pages, emails and audit trails take months to build well.
Sign · E-signature API
An e-signature API that sends documents in one API call.
The Flaxxa Sign API lets your product send a document for e-signature in one call: the document as a URL, base64 or HTML, the signers and their fields. It returns a signing link per signer to redirect to, fires an HMAC-signed webhook when the envelope completes, and serves the signed PDF and certificate by id.
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sign.flaxxa.com / api
One API call
flx_live_••••a1b2POST /v1/sign/envelopes/send
{ "external_id": "PROPOSAL-42", … }
→ 201 Created
status: sentsigning_links: 2
webhook envelope.completed HMAC ✓
Signed PDF + certificate120 req/min
- To send an envelope
- 1 call
- Redirect your users
- Signing links
- HMAC-signed
- Webhooks
- Your own ids
- external_id
01 / 04
Why not build e-signatures yourself?
Sending users elsewhere
Asking users to sign in a separate tool breaks your flow.
Reconciling by hand
Matching signed documents back to your records is fiddly without shared ids.
02 / 04
How does the Flaxxa Sign API work?
Send in one call
POST a document, recipients and fields to /envelopes/send, and Flaxxa Sign creates and sends the envelope.
Redirect to sign
Take the signing link for each signer and send your user there, instead of waiting for the email.
Hear back
HMAC-signed webhooks fire on sent, opened, signed, declined and completed.
Reconcile
Match everything by the external_id you set, and fetch the signed PDF and certificate.
03 / 04
What does the API give you?
One-call send
Documents (URL, base64 or HTML pages), recipients, fields and order in a single POST.
Signature blocks in HTML
A signature-block element in your HTML becomes that signer's exact spot.
Signing links
A URL per signer to redirect to, instead of waiting for the email.
Webhooks
Subscribe to the envelope events; every payload is HMAC-SHA256 signed.
Idempotent writes
An Idempotency-Key header means a retried send doesn't send twice.
Fetch the proof
The signed PDF, audit trail and certificate by the envelope's id.
04 / 04
What changes with an API?
No signing system to build
Add e-signatures to your product without building the hard parts.
Fits your flow
Send your user straight to their signing link from your own app.
Reconciles itself
Your own ids tie every signed document back to your records.
Keep exploring
More Sign capabilities
Send for signature
Send documents for e-signature: upload a PDF or write one, place fields per signer, choose sequential or parallel signing, countersign and send.
Audit trail
Every Flaxxa Sign envelope logs consent and each step with time and IP address, and gives you a signing certificate with document and signature hashes.
Tracking
Track every envelope: draft, sent, in progress, completed, declined, voided or expired. See who's still to sign, send a reminder or void it.
FAQ
E-signature API: common questions
A way for your own software to send documents for signature, track them and fetch the signed result, without anyone using a separate e-signature app.
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