API docs

Base URL: https://api.slipkiln.com. All requests and responses are JSON, except render endpoints, which return application/pdf.

Quickstart

Get a free API key (50 documents/month).
Save it in your shell: export SLIPKILN_KEY=sk_…
Send HTML or JSON and get a PDF back.

curl -X POST https://api.slipkiln.com/v1/render/template \
  -H "Authorization: Bearer $SLIPKILN_KEY" \
  -H "Content-Type: application/json" \
  -d '{"template":"invoice","data":{"number":"INV-1001","currency":"USD",
       "customer":{"name":"Acme Co."},
       "items":[{"description":"Consulting","qty":10,"unit_price":120}]}}' \
  -o invoice.pdf

const res = await fetch("https://api.slipkiln.com/v1/render/template", {
  method: "POST",
  headers: { Authorization: `Bearer ${process.env.SLIPKILN_KEY}`, "Content-Type": "application/json" },
  body: JSON.stringify({
    template: "invoice",
    data: { number: "INV-1001", currency: "USD", customer: { name: "Acme Co." },
            items: [{ description: "Consulting", qty: 10, unit_price: 120 }] },
  }),
});
if (!res.ok) throw new Error((await res.json()).message);
await require("fs/promises").writeFile("invoice.pdf", Buffer.from(await res.arrayBuffer()));

import os, requests

r = requests.post(
    "https://api.slipkiln.com/v1/render/template",
    headers={"Authorization": f"Bearer {os.environ['SLIPKILN_KEY']}"},
    json={"template": "invoice",
          "data": {"number": "INV-1001", "currency": "USD", "customer": {"name": "Acme Co."},
                   "items": [{"description": "Consulting", "qty": 10, "unit_price": 120}]}},
    timeout=30,
)
r.raise_for_status()
open("invoice.pdf", "wb").write(r.content)

Authentication

Send your key as a bearer token: Authorization: Bearer sk_…. Keys are shown once at signup and stored only as a hash, so we can't recover a lost key. Email support@slipkiln.com if you lose yours. Keep keys server-side. Don't ship them in browser or mobile code.

Create a key with POST /v1/signup {"email":"you@company.com"} → 201 {"api_key":"sk_…","plan":"free","monthly_limit":50}. One account per email.

POST/v1/render/html

Render your own HTML/CSS with a headless Chromium.

Field	Type
`html`	string, required	Full HTML document or fragment (≤ 2 MB). Images, fonts and CSS must be inlined as `data:` URIs. External URLs are blocked.
`options`	object	See render options.

curl -X POST https://api.slipkiln.com/v1/render/html \
  -H "Authorization: Bearer $SLIPKILN_KEY" -H "Content-Type: application/json" \
  -d '{"html":"<h1 style=\"color:#0f766e\">Hello PDF</h1>","options":{"format":"Letter","margin":{"top":"20mm"}}}' \
  -o hello.pdf

const res = await fetch("https://api.slipkiln.com/v1/render/html", {
  method: "POST",
  headers: { Authorization: `Bearer ${process.env.SLIPKILN_KEY}`, "Content-Type": "application/json" },
  body: JSON.stringify({ html: "<h1>Hello PDF</h1>", options: { format: "Letter" } }),
});
const pdf = Buffer.from(await res.arrayBuffer());

r = requests.post("https://api.slipkiln.com/v1/render/html",
    headers={"Authorization": f"Bearer {os.environ['SLIPKILN_KEY']}"},
    json={"html": "<h1>Hello PDF</h1>", "options": {"format": "Letter"}}, timeout=30)
open("hello.pdf", "wb").write(r.content)

Successful responses include x-usage-month: documents rendered by your account this month.

POST/v1/render/template

{"template": "invoice" | "receipt" | "certificate", "data": {…}, "options": {…}}. All text is HTML-escaped. GET /v1/templates (no auth) returns every template with full example data.

Templates

Shared brand object (all templates):

`brand.name`	string	Shown when no logo is given
`brand.logo`	string	Base64 `data:image/png\|jpeg\|gif\|webp\|svg+xml;base64,…` only
`brand.color`	string	Hex accent color, e.g. `#0f766e`
`brand.email`, `brand.website`	string	Contact lines
`brand.address`	string[]	Address lines

invoice (A4)

`number`	string	Invoice number
`issue_date`, `due_date`	string	Printed as given
`currency`	string	ISO 4217, default `USD`
`customer`	object	`name`, `email`, `address` (string[])
`items`	array	`{description, qty, unit_price}`, max 500. Totals are computed.
`tax_rate`	number	Percent, e.g. `8.25`
`notes`	string	Footer note

receipt (A5)

`number`, `date`	string
`payment_method`	string	e.g. "Visa •••• 4242"
`currency`, `tax_rate`, `items`		Same as invoice
`customer.name`	string

certificate (A4 landscape)

`title`	string	e.g. "Certificate of Completion"
`recipient`	string	Name
`description`	string	Body text
`date`	string
`signer`	object	`name`, `title`
`certificate_id`	string	Printed bottom-right

Render options

`format`	`A4` \| `A5` \| `Letter` \| `Legal`
`landscape`	boolean
`margin`	`{top,right,bottom,left}`, values like `10mm`, `0.5in`, `20px`
`print_background`	boolean, default true
`javascript`	boolean, default false (HTML endpoint only; network stays blocked)

Account & billing

`GET /v1/me`	Plan and usage this month
`POST /v1/billing/checkout` `{"plan":"starter\|growth\|scale"}`	Returns `{url}` to Stripe Checkout
`POST /v1/billing/change-plan` `{"plan":…}`	Switch paid plans (prorated)
`POST /v1/billing/portal`	Returns `{url}` to the Stripe billing portal (card, invoices, cancel)

Or use the Billing page.

Errors

Errors are JSON: {"error":"code","message":"…"}.

Status	error	Meaning
400	`invalid_request`, `invalid_template`, `invalid_email`, `invalid_plan`	Bad input
401	`unauthorized`	Missing/invalid key
402	`quota_exceeded`	Free plan's 50 docs used this month
408	`render_timeout`	Render took over 15 s
409	`email_exists`, `already_subscribed`	Conflict
413	`render_too_large` / body too large	Request > 2 MB or PDF > 20 MB
422	`render_failed`	Chromium could not render
429		Rate limited; retry after the `retry-after` header
503	`render_busy`	Temporarily at capacity; retry with backoff

Limits & security

60 requests/minute per key; signup 5/hour per IP.
Free: 50 successful documents per calendar month (UTC). Failed renders don't count. Paid plans: included documents, then per-document overage (see pricing).
Request body ≤ 2 MB; PDF ≤ 20 MB; 15 s per render.
Rendering runs in an isolated Chromium with no network access: only data: URIs load. JavaScript is off unless you set options.javascript.
Documents are processed in memory and not stored after delivery.