Convert documents, spreadsheets and tables to Markdown & CSV.
Convert directly between PDF (.pdf), PowerPoint (.pptx / .ppt), Excel (.xlsx), CSV, Word documents (.docx / .doc), JSON, YAML and HTML. Dramatically save tokens in AI models like Claude, Gemini and Microsoft Copilot.
Why Markdown for LLM & AI Prompts?
Reduce noise, minimize token costs, and improve AI understanding instantly.
Save 40% to 60% Tokens
Complex HTML, DOCX and PDF structures contain heavy markup. Markdown retains only the semantic core of your content.
Higher Comprehension Accuracy
Models like GPT-4o, Claude 3.5 Sonnet and Gemini 1.5 Pro are optimally trained on Markdown tables and headers.
More Data in your Context Window
Thanks to compact data, you can fit more relevant documents into a single AI context without exceeding limits.
Give Claude a custom tool / skill to automatically call the slim-down API for complex input.
tools = [{
"name": "slim_down_convert",
"description": "Markdown parser",
"input_schema": {...}
}]Convert large Word reports (.docx) to Markdown and inject them directly into the context window of Claude 3.5 / 3.7.
md = slimdown.convert_file("doc.docx")
msg = claude.messages.create(
model="claude-3-7-sonnet",
messages=[{"role":"user","content":...}]
)Transform Excel sheets (.xlsx) and CSV data into structured Markdown tables for data analysis with Gemini 2.0.
table = slimdown.convert(csv, "markdown")
model = genai.GenerativeModel(...)
res = model.generate_content(...)Copy prompt instructions to Claude Projects, ChatGPT Custom GPTs, Copilot Chat, or .cursorrules.
Use the slim-down API via
POST /api/convert (Bearer <token>)
to simplify all data first.Features
Built for reliable and structured document conversion.
Automatic Detection
Automatically detect JSON, YAML, HTML tables, CSV/TSV, or plain text on input.
PDF, Word & PowerPoint Parsing
Import .pdf, .docx, .doc, .pptx, and .ppt files and directly convert formatting, tables, slides, and headers to clean Markdown.
AI Token Reduction
Optimize prompts for Claude, Gemini, and Copilot by filtering out redundant tags and formatting noise.
Cross-device Sync
Log in with Google or email and access your saved documents instantly across any device.
Powerful REST API
Integrate document conversion directly into your own backend pipelines, n8n workflows, or Python AI agents.
Simple Authentication
Supports both Authorization: Bearer and X-API-Key headers with secure persistence.
Text & File Uploads
Process PDF (.pdf), Word (.docx/.doc), PowerPoint (.pptx/.ppt), Excel (.xlsx), HTML, CSV, JSON, and YAML directly via REST endpoints.
Cloud Document Sync
Save conversion results directly to your account using save: true and access them on all your devices.
curl -X POST https://slim-down.nl/api/convert \
-H "Authorization: Bearer <JOUW_API_SLEUTEL>" \
-H "Content-Type: application/json" \
-d '{
"input": "# Project Notitie\n- Taak 1: Afgerond\n- Taak 2: In behandeling",
"target_format": "html"
}'Supported File Formats
Effortlessly convert between document, spreadsheet and data structures.
XLSX
CSV / TSV
DOCX
DOC
PPTX
PPT
Markdown
JSON
YAML
HTML
Text
Frequently Asked Questions
Answers to the questions we get asked most about slim-down.
Is slim-down free to use?
Yes. Without an account you get up to 3 free conversions per day. A free account gives you unlimited conversions and lets you save and sync documents across devices.
Which file formats does slim-down support?
slim-down converts PDF, Word (.docx/.doc), PowerPoint (.pptx/.ppt), and Excel (.xlsx) via upload, and CSV, JSON, YAML, and HTML as text, into clean Markdown, plain text, or other structured formats.
Why use Markdown for AI prompts like Claude, ChatGPT, or Gemini?
Markdown has no unnecessary formatting or XML tags, which costs up to 60% fewer tokens than Word or HTML documents in the same prompt or context window, while keeping the semantic structure intact.
Does slim-down store my documents?
Only if you choose to. Without an account, nothing is stored; with an account you can optionally save conversions to find them across devices, and delete them again at any time.
Is there a REST API for automation?
Yes. The REST API supports both text/JSON and file uploads, authenticated with a Bearer token or API key, built for pipelines, scripts, and AI agents.