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Remote templates

A remote template fetches its output from another HTTP service instead of rendering HTML locally. It is defined by a single template.http.hbs file: a Handlebars template that renders a raw HTTP request. PDF Server executes that request and returns the response body (typically a PDF) as the result.

remote-invoice/
  template.http.hbs
  schema.json
  examples/
    minimal.json
{{! template.http.hbs — renders a raw HTTP request }}
GET {{documentUrl}} HTTP/1.1
Host: {{host}}
Accept: application/pdf

The rendered request is parsed and executed; a non-2xx response (status > 299) is an error. The most common use is inside a composition to stitch a remotely-produced PDF together with locally-rendered pages (see the remote-merge example in the Gallery).

Security: read this before using request data in the URL​

The request text is rendered from template data. If any part of the URL, host, or headers comes from untrusted request data, this becomes a Server-Side Request Forgery vector: a caller could make your server fetch internal endpoints (for example a cloud metadata service), and newline characters in a value can inject additional headers.

Safe usage:

  • Only build remote requests from trusted data (fixed hosts, internal configuration), never from end-user input.
  • Prefer pinning the scheme and host in the template and passing only an opaque identifier as data.
  • Deploy with an egress network policy that blocks private/link-local ranges.

See Security model and Proved security issues for the full analysis and mitigations.