Get started →

If you prefer not to use an SDK, you can call the Maildeno Render API directly over HTTP.

Base URL

https://api.maildeno.com

Authentication

All requests require a Bearer token in the Authorization header:

Authorization: Bearer sk_live_your_api_key

Endpoints

POST /v1/sdk/render

Render a template and return the output string.

Request

POST /v1/sdk/render
Content-Type: application/json
Authorization: Bearer <API_KEY>
{
  "template_id": "550e8400-e29b-41d4-a716-446655440000",
  "target": "html",
  "dynamic_data": {
    "merge_tags": {
      "text": {
        "name": "Noruwa",
        "company": "Maildeno"
      },
      "url": {
        "reset_url": "https://app.example.com/reset/abc123"
      },
      "attr": {
        "alt_text": "Banner image"
      }
    },
    "context": {
      "plan": "pro",
      "country": "usa"
    }
  }
}

Request fields

Field Type Required Description

template_id

string (UUID v4)

✓

The template to render.

target

string

"html" (default), "react-email", or "mjml".

dynamic_data

object

See below.

dynamic_data.merge_tags

object

{ text?, url?, attr? } — all optional sub-objects.

dynamic_data.context

object

Flat map of string | number | boolean values.

Response — 200 OK

The response body is the raw rendered string (not JSON-wrapped):

<!DOCTYPE html>
<html lang="en">
...
</html>

Content-Type is text/html for html target, text/plain for react-email and mjml.

Error responses

Status Code Description

401

INVALID_API_KEY

Missing, malformed, revoked, or expired key.

403

FORBIDDEN

Key does not have scope for the requested target.

404

TEMPLATE_NOT_FOUND

Template ID does not exist.

422

RENDER_ERROR

Request body is invalid or render pipeline failed. Includes issues array.

 
{
  "code": "RENDER_ERROR",
  "message": "template_id is not a valid UUID",
  "issues": [
    {
      "loc": ["body", "template_id"],
      "msg": "Input should be a valid UUID, invalid character: expected an optional prefix of `urn:uuid:` followed by [0-9a-fA-F-], found `n` at 1",
      "type": "uuid_parsing"
    }
  ]
}

curl examples

# Minimal — HTML, no dynamic data
curl -X POST https://api.maildeno.com/v1/sdk/render \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $MAILDENO_API_KEY" \
  -d '{"template_id": "550e8400-e29b-41d4-a716-446655440000"}'
# Full request with merge tags and context
curl -X POST https://api.maildeno.com/v1/sdk/render \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $MAILDENO_API_KEY" \
  -d '{
    "template_id": "550e8400-e29b-41d4-a716-446655440000",
    "target": "html",
    "dynamic_data": {
      "merge_tags": {
        "text": { "name": "Noruwa", "company": "Maildeno" }
      },
      "context": { "plan": "pro" }
    }
  }'

Key management endpoints

POST /api/v1/keys

Create a new API key.

curl -X POST https://api.maildeno.com/api/v1/keys \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <ADMIN_KEY>" \
  -d '{"name": "Production HTML", "targets": ["html"]}'
{
  "id": "key_01abc...",
  "name": "Production HTML",
  "key": "sk_live_...",   // shown once — copy it now
  "targets": ["html"],
  "created_at": "2025-01-01T00:00:00Z"
}