Convert Markdown to PDF in Node.js (TypeScript)

What you need

• An API key. Create one in the app under API keys and export it as FORMFEED_API_KEY. A test key (ff_test_…) is right for trying things out. See the quick start.
• Node.js (TypeScript). You need Node.js 22 or newer and the @formfeed/sdk package, which has no dependencies of its own.
• A Markdown file. report.md next to the program, up to 1 MB. A sample is further down.

npm install @formfeed/sdk
npm install --save-dev tsx   # runs the .ts file directly

The program

The program reads report.md, posts it as markdown with bookmarks from its headings, waits for the result when the API answers 202, stops with the API’s message when something is wrong, and saves the PDF.

import { readFile, writeFile } from 'node:fs/promises';
import { Formfeed } from '@formfeed/sdk';

const formfeed = new Formfeed({ apiKey: process.env.FORMFEED_API_KEY! });
const markdown = await readFile('report.md', 'utf8');

// a problem answer (4xx, 5xx) throws a FormfeedError with the API's code, title and detail
let render = await formfeed.renders.create({
  markdown,
  settings: {
    pdf: { outline: true },
  },
});
// not done within 60 seconds: the API answered 202 and the render goes on in the background
if (render.status !== 'succeeded') render = await formfeed.renders.waitFor(render.id);
if (render.status === 'failed') throw new Error(`render failed: ${JSON.stringify(render.error)}`);

await writeFile('report.pdf', await formfeed.renders.download(render));
console.log(render.id, render.page_count, 'page(s),', render.units, 'unit(s)');

Run it

It prints the render’s id, the page count and the units it cost, and report.pdf lies next to the program.

export FORMFEED_API_KEY=ff_test_...
npx tsx render.ts

What is particular about Node.js (TypeScript)

• Top-level await. The file uses await outside a function, so it must be an ES module: keep "type": "module" in package.json or name it .mts.
• Retries are built in. The SDK sends an Idempotency-Key with every render and retries 429, 503 and network errors up to three times with backoff, with the same key: a retry of a request that was answered already gets that answer back instead of a second render.
• Errors are typed. A problem answer throws a FormfeedError whose code is the API’s error code (template_not_found, quota_exceeded, …); catch it where you would show the user something useful.
• Runs anywhere fetch does. The SDK uses only web APIs, so the same call works in Deno, Bun and Cloudflare Workers; only the file access differs.

A Markdown file with a title

The front matter gives the PDF its title and author; without one the first heading is the title. A line \newpage starts a new page, and a link to a heading works inside the PDF:

---
title: Release notes 2.4
author: Fennlor Studio GmbH
---

# Release notes 2.4

## What is new

- Faster previews, see [the numbers](#numbers)
- Footnotes in the export[^1]
- [x] Tested on every plan

## Numbers

| Step    | Before | After  |
| :------ | -----: | -----: |
| Preview | 840 ms | 310 ms |
| Export  | 2.1 s  | 1.4 s  |

\newpage

## Thanks

To everyone who reported a problem.

[^1]: From version 2.4 on.

What the settings control

• Look. settings.markdown.theme is document, which styles the text, in the brand kit’s fonts and colour where the workspace has one, or none; settings.markdown.css comes after it.
• Raw HTML. Shown as text by default. settings.markdown.html: "allow" writes it as it stands, for Markdown you wrote yourself, never for text from your users or a model.
• Line breaks. settings.markdown.breaks: true makes a single line break a line break, for text from a chat.
• Paper, header and footer. paper, margin, header.html and footer.html work as for HTML; elements with the classes pageNumber and totalPages show the page numbers.

Placeholders in the Markdown

Add "engine": "jinja2" (or liquid, handlebars) and a data object, and {{ … }} in the text is filled before it is read as Markdown, with all helpers. The Markdown guide has the rest.

When the API says no

• One shape for every error. Errors are problem documents (RFC 9457) with type, title, status, detail, a stable code and the request_id to quote to support; the type URL leads to a page about that error. The list is in the error reference.
• The usual ones. 401 unauthorized for a missing or revoked key, 404 template_not_found for a wrong template name, 422 template_runtime_error when the template fails on the data, 429 rate_limited above the plan’s requests per second, 402 quota_exceeded when the Free plan’s units are used up (a paid plan bills extra units up to its hard cap).
• Retry safely. Send an Idempotency-Key header with the POST, and repeat the request with the same key when you do not know whether the first attempt arrived: for 24 hours the key returns the first answer instead of rendering and billing again. The answer is stored once the first attempt has been answered, so do not retry while it may still run; and problems below 500 are stored too, so a corrected request needs a new key.

The job around this program

This guide is one program. What the job needs around it, from the template to the limits and the price, is on the page Markdown to PDF API.

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