Skip to main content
Get a credential on API keys, point it at the base URL below, and every endpoint is described in full in the API reference.

​
The basics

Authentication is one header, one step. The prefix is stored in clear so a leaked key is greppable and traceable to an organisation; the secret is stored only as a hash, so nobody — including us — can recover it. See Authentication. The OpenAPI document is public, needs no key, is readable cross-origin from a browser, and is generated from the running code — so it cannot describe an endpoint the API does not serve. The reference on this site is rendered from it. Generate a client from it. Documents are checked by the bytes, not the extension, so renaming a file changes nothing either way. A Word .docx is converted to PDF on our side, and the converted PDF is what fields are placed on and what gets signed — your original is kept unchanged. Text tags survive that render. The older .doc format is not accepted. Through the API a document travels base64-encoded inside the JSON body, which is what sets the API’s ceiling in the table above, whatever the document’s format or page count; the upload screen, which sends the file itself, allows more.

​
Before the first call

What the reference assumes you already know, and worth reading before the first call: each is a mistake that is cheap to avoid and expensive to make after a document has been sent.