Markdown to Word API: Developer Guide for Document Conversion
Manual document conversion does not scale. Whether you are generating reports from a CI/CD pipeline, exporting user-authored content from a CMS, or building a SaaS product that delivers polished Word documents, you need a programmatic way to turn Markdown into .docx files. A Markdown to Word API lets you automate that entire workflow with a single HTTP request — no desktop software, no browser interaction, and no human in the loop. This guide covers everything you need to integrate a conversion API into your stack: endpoint references, code samples in three languages, authentication patterns, advanced features like batch processing and webhooks, and battle-tested error-handling strategies.
Why Use an API for Markdown to Word Conversion?
Teams across engineering, product, and documentation frequently write in Markdown because it is lightweight, version-control friendly, and universally supported by developer tools. However, stakeholders outside the engineering org — clients, legal departments, executives — overwhelmingly expect Word documents. Bridging that gap manually is tedious and error-prone. An API-driven approach eliminates the friction entirely and brings several concrete advantages.
Automation at Scale
Convert hundreds or thousands of Markdown files to Word without any human intervention. Trigger conversions from scripts, pipelines, or scheduled jobs. A single API call replaces what would otherwise be minutes of manual copying, pasting, and formatting in a word processor.
CI/CD Integration
Embed document generation directly into your build and deployment pipelines. Every time documentation is merged to main, produce an up-to-date Word deliverable automatically. This guarantees that published documents are always in sync with the source of truth in your repository.
Consistent Output
APIs apply the same conversion logic every time. Headings, tables, code blocks, images, and lists are rendered identically across every document. No more variations caused by different people using different tools or settings on different machines.
Time Savings
An API call typically completes in under two seconds. Compare that to the three-to-five minutes it takes to open a converter, paste content, tweak formatting, and download the file manually. Over a team producing dozens of documents per week, the savings are substantial.
Beyond these core benefits, an API-first strategy future-proofs your document workflow. As your product grows, you can layer on features — templating, watermarking, metadata injection — without rearchitecting the conversion step. The API becomes a stable contract that the rest of your system depends on, while the implementation behind it can evolve independently.
For SaaS platforms, offering Word export as a feature is a significant differentiator. Users expect to be able to download their content in a standard format. By integrating a Markdown to Word API on the backend, you can provide a seamless "Export to Word" button that converts content server-side and streams the result to the client. No browser extensions, no third-party plugins — just a clean, one-click experience.
API Endpoint Reference
The Markdown to Word conversion API exposes a single, focused endpoint. You send Markdown content in the request body and receive a .docx binary in the response. Below is the full specification.
/api/convert
Converts a Markdown string into a Word document (.docx) and returns the binary file.
Request Headers
| Header | Value | Required |
|---|---|---|
| Content-Type | application/json |
Yes |
| Authorization | Bearer <API_KEY> |
Yes |
| Accept | application/vnd.openxmlformats-officedocument.wordprocessingml.document |
Optional |
Request Body (JSON)
| Field | Type | Description |
|---|---|---|
| markdown | string | The raw Markdown content to convert. Required. |
| filename | string | Desired filename for the output (without extension). Defaults to document. |
| template | string | Template ID to apply custom styles. Optional. |
| options | object | Advanced conversion settings (page size, margins, TOC). Optional. |
Example Request Body
{
"markdown": "# Project Report\n\nThis is the executive summary.\n\n## Key Findings\n\n- Revenue grew 23% YoY\n- Customer satisfaction at 94%\n\n## Data\n\n| Metric | Q1 | Q2 |\n|--------|-----|-----|\n| Users | 1.2M | 1.5M |",
"filename": "quarterly-report",
"template": "corporate-default",
"options": {
"pageSize": "A4",
"margins": { "top": "2.54cm", "bottom": "2.54cm", "left": "3.17cm", "right": "3.17cm" },
"tableOfContents": true
}
}
Response
| Status | Content-Type | Description |
|---|---|---|
| 200 | application/vnd.openxml... | Binary .docx file. The Content-Disposition header contains the filename. |
| 400 | application/json | Invalid request. Missing or malformed markdown field. |
| 401 | application/json | Missing or invalid API key. |
| 429 | application/json | Rate limit exceeded. Check Retry-After header. |
| 500 | application/json | Server error during conversion. Safe to retry with exponential backoff. |
Code Examples
Below are complete, copy-paste-ready examples for the three most common environments. Each example sends a Markdown string to the API and saves the resulting .docx file to disk. Replace YOUR_API_KEY with your actual key.
import requests
import os
# Configuration
API_URL = "https://www.markdown-to-word.online/api/convert"
API_KEY = os.environ.get("MD_TO_WORD_API_KEY", "YOUR_API_KEY")
# Read Markdown from a file
with open("README.md", "r", encoding="utf-8") as f:
markdown_content = f.read()
# Make the API request
response = requests.post(
API_URL,
json={
"markdown": markdown_content,
"filename": "project-docs",
"options": {
"pageSize": "A4",
"tableOfContents": True
}
},
headers={
"Authorization": f"Bearer {API_KEY}",
"Content-Type": "application/json"
},
timeout=30
)
# Handle the response
if response.status_code == 200:
with open("project-docs.docx", "wb") as f:
f.write(response.content)
print("Conversion successful: project-docs.docx")
elif response.status_code == 429:
retry_after = response.headers.get("Retry-After", 60)
print(f"Rate limited. Retry after {retry_after} seconds.")
else:
print(f"Error {response.status_code}: {response.json()}")
import { writeFileSync, readFileSync } from "node:fs";
const API_URL = "https://www.markdown-to-word.online/api/convert";
const API_KEY = process.env.MD_TO_WORD_API_KEY || "YOUR_API_KEY";
async function convertMarkdownToWord(markdownPath, outputPath) {
const markdown = readFileSync(markdownPath, "utf-8");
const response = await fetch(API_URL, {
method: "POST",
headers: {
"Content-Type": "application/json",
"Authorization": `Bearer ${API_KEY}`
},
body: JSON.stringify({
markdown,
filename: "output-document",
options: { pageSize: "A4" }
})
});
if (!response.ok) {
const error = await response.json();
throw new Error(`API error ${response.status}: ${error.message}`);
}
const buffer = Buffer.from(await response.arrayBuffer());
writeFileSync(outputPath, buffer);
console.log(`Saved: ${outputPath}`);
}
// Usage
convertMarkdownToWord("./README.md", "./output.docx");
# Basic conversion
curl -X POST "https://www.markdown-to-word.online/api/convert" \
-H "Content-Type: application/json" \
-H "Authorization: Bearer YOUR_API_KEY" \
-d '{"markdown": "# Hello World\n\nThis is a **test** document.", "filename": "test"}' \
-o test.docx
# Convert from a file
curl -X POST "https://www.markdown-to-word.online/api/convert" \
-H "Content-Type: application/json" \
-H "Authorization: Bearer YOUR_API_KEY" \
-d "$(jq -n --arg md "$(cat README.md)" '{markdown: $md, filename: "readme"}')" \
-o readme.docx
# With advanced options
curl -X POST "https://www.markdown-to-word.online/api/convert" \
-H "Content-Type: application/json" \
-H "Authorization: Bearer YOUR_API_KEY" \
-d '{
"markdown": "# Report\n\n## Section 1\n\nContent here.",
"filename": "report",
"template": "corporate-default",
"options": {"pageSize": "Letter", "tableOfContents": true}
}' \
-o report.docx
Authentication & Rate Limits
Every API request must include a valid API key for authentication. Rate limits are enforced per key to ensure fair usage and platform stability. Understanding these constraints upfront will help you design robust integrations that handle edge cases gracefully.
API Key Authentication
Include your API key in the Authorization header using the Bearer scheme. API keys are 40-character alphanumeric strings prefixed with mdw_.
Authorization: Bearer mdw_a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6q7r8s9t0
Security Best Practice
Never hard-code API keys in your source code. Use environment variables or a secrets manager (AWS Secrets Manager, HashiCorp Vault, or your CI/CD platform's secret storage). Rotate keys periodically and use separate keys for development and production environments.
Rate Limiting Policies
Rate limits are applied per API key using a sliding window algorithm. When you exceed your limit, the API returns a 429 Too Many Requests status with a Retry-After header indicating how many seconds to wait.
| Plan | Requests / Minute | Requests / Day | Max File Size |
|---|---|---|---|
| Free | 10 | 100 | 500 KB |
| Pro | 60 | 5,000 | 5 MB |
| Enterprise | 300 | Unlimited | 25 MB |
Rate Limit Response Headers
Every API response includes headers that let you monitor your current usage in real time. Use these to implement proactive throttling before hitting limits.
| Header | Description |
|---|---|
| X-RateLimit-Limit | Maximum requests allowed in the current window. |
| X-RateLimit-Remaining | Requests remaining in the current window. |
| X-RateLimit-Reset | Unix timestamp when the current window resets. |
Advanced Features
Beyond basic conversion, the API supports several advanced capabilities that let you tailor the output to your exact requirements. These features are available on Pro and Enterprise plans.
Custom Templates
Upload a .docx reference template via the dashboard, and the API will apply its styles — fonts, heading sizes, colors, header/footer layouts — to every document you generate. This is invaluable for organizations that need brand-consistent output. Templates are stored server-side and referenced by ID.
{
"markdown": "# Quarterly Review\n\nContent goes here...",
"template": "tmpl_acme_corp_2026",
"options": {
"headerText": "ACME Corporation - Confidential",
"footerText": "Page {PAGE} of {NUMPAGES}"
}
}
Template styles cascade: heading fonts, paragraph spacing, table borders, and list bullet styles from your template override the API defaults. Elements not defined in the template fall back to the system defaults.
Batch Conversion
When you need to convert multiple documents at once, the batch endpoint accepts an array of conversion jobs and returns a ZIP archive containing all generated files. This is significantly more efficient than sending individual requests because the server can process jobs in parallel and you save on network round-trips.
POST /api/convert/batch
{
"jobs": [
{ "markdown": "# Doc 1\n\nFirst document content.", "filename": "doc-1" },
{ "markdown": "# Doc 2\n\nSecond document content.", "filename": "doc-2" },
{ "markdown": "# Doc 3\n\nThird document content.", "filename": "doc-3" }
],
"template": "corporate-default"
}
The batch endpoint supports up to 50 documents per request. Each job in the array accepts the same parameters as the single-conversion endpoint. The response is a ZIP file with Content-Type: application/zip.
Webhooks
For long-running or large batch conversions, you can provide a webhook URL. Instead of waiting for the response synchronously, the API will return a 202 Accepted status immediately and POST the result to your webhook endpoint when conversion is complete. This pattern is ideal for serverless architectures and event-driven workflows where you want to avoid holding connections open.
{
"markdown": "# Large Document\n\n...",
"filename": "large-report",
"webhook": {
"url": "https://your-server.com/webhooks/conversion-complete",
"secret": "whsec_your_webhook_signing_secret"
}
}
Webhook payloads include an HMAC-SHA256 signature in the X-Signature-256 header, computed with your webhook secret. Always verify this signature before processing the payload to prevent spoofed requests. The payload body contains a download_url that remains valid for 24 hours.
Error Handling & Best Practices
A well-integrated API client anticipates failures and handles them gracefully. The Markdown to Word API uses standard HTTP status codes and returns structured JSON error bodies. Below are the most common error scenarios and the recommended strategies for dealing with them.
Common Error Responses
400 Bad Request
The markdown field is missing, empty, or exceeds the maximum size for your plan. Validate input on the client side before sending the request. Check that the JSON body is well-formed and that all required fields are present.
{ "error": "INVALID_REQUEST", "message": "The 'markdown' field is required and must be a non-empty string." }
401 Unauthorized
The API key is missing, malformed, expired, or revoked. Double-check that the Authorization header is formatted correctly as Bearer <key> with exactly one space between "Bearer" and the key.
429 Too Many Requests
You have exceeded the rate limit for your plan. Read the Retry-After header and wait that many seconds before retrying. Implement a queue or token-bucket on the client side to prevent bursts from triggering this error.
500 Internal Server Error
An unexpected server-side failure occurred during conversion. These are safe to retry. Use exponential backoff: wait 1 second, then 2, then 4, up to a maximum of 30 seconds. If the error persists after 3 retries, log the request ID from the X-Request-ID header and contact support.
Integration Best Practices
Use Exponential Backoff with Jitter
When retrying failed requests, add a random jitter (0 to 500ms) to the backoff interval. This prevents thundering herd problems where many clients retry at exactly the same time after a rate-limit window resets.
Implement Idempotency
Include an Idempotency-Key header with a unique value (UUID v4) for each logical conversion request. If you need to retry a request that may have partially succeeded, the server will return the cached result rather than processing the conversion again. This prevents duplicate documents in your workflow.
Set Reasonable Timeouts
Configure a 30-second timeout for single conversions and 120 seconds for batch requests. If the server has not responded within that window, the conversion has likely failed and you should retry. Do not set timeouts shorter than 10 seconds — complex documents with many tables or images legitimately take a few seconds to process.
Validate Markdown Before Sending
Run basic validation on the client side: check that the Markdown string is non-empty, within the size limit for your plan, and valid UTF-8. Catching these issues before the network request saves latency and avoids burning API quota on requests that will always fail.
Log Request IDs
Every API response includes an X-Request-ID header. Log this value alongside your application logs. When you contact support about a failed conversion, providing the request ID allows the team to trace the exact processing pipeline and diagnose the issue significantly faster.
Frequently Asked Questions
What Markdown features are supported by the API?
The API supports the full CommonMark specification plus GitHub Flavored Markdown (GFM) extensions. This includes headings (H1 through H6), bold, italic, strikethrough, inline code, fenced code blocks with language identifiers, ordered and unordered lists, nested lists, blockquotes, horizontal rules, links, images (referenced by URL), tables with alignment, task lists (checkboxes), and footnotes. Mathematical expressions in LaTeX syntax (using dollar signs) are rendered as formatted equations in the output document.
Can I convert Markdown to PDF instead of Word?
Yes. The same API supports PDF output. Set the format field to "pdf" in your request body (the default is "docx"). PDF output uses a headless Chromium renderer to produce pixel-perfect documents. All the same options — templates, page size, margins, table of contents — apply to both formats. You can also use the PDF vs Word comparison guide to decide which format best fits your use case.
Is there a file size limit for Markdown input?
Yes, the limit depends on your plan. Free accounts can send up to 500 KB of Markdown per request, Pro accounts up to 5 MB, and Enterprise accounts up to 25 MB. These limits refer to the raw Markdown text size, not the generated output. If your document includes many external images referenced by URL, those images are fetched server-side and do not count toward the input limit. For very large documents that exceed the Enterprise limit, consider splitting them into chapters and using the batch endpoint to convert them separately.
How do I handle images in my Markdown?
Use standard Markdown image syntax with absolute URLs: . The API server fetches each image at conversion time and embeds it directly into the Word document. Supported formats are PNG, JPEG, GIF, and SVG. Images must be publicly accessible (no authentication required). If you need to include private images, you can base64-encode them inline using data URIs, though this increases the request body size. For optimal results, use images with a resolution of at least 150 DPI.
Is my data secure? Do you store the Markdown content?
All API communication is encrypted via TLS 1.3. Your Markdown content is processed in memory and is never written to persistent storage. Generated documents are cached in ephemeral storage for up to 60 minutes (to support webhook delivery and retry scenarios) and then permanently deleted. We do not log, index, or analyze the content of your documents. Enterprise customers can request a dedicated processing environment with additional isolation guarantees. For full details, see our Privacy Policy.
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