windows-iso-downloader

A clean, open-source tool for obtaining official Windows ISO files directly from Microsoft's CDN — without a Windows machine, the Media Creation Tool, or browser restrictions.

Live: msdl.tech-latest.com · By: TechLatest

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What it does

MSDL replicates the session flow that Microsoft uses to serve ISO download links — identical to the approach used by Rufus/Fido. You get the exact same signed CDN URL Microsoft would give you, just without the browser requirement.

• ✅ Direct Microsoft CDN links — no proxying of actual file data
• ✅ 38 languages per consumer release
• ✅ ARM64 + x64 + x86 support
• ✅ Windows Server 2016–2025 and Windows 11 Enterprise evaluation ISOs
• ✅ No account, no browser lock, no ads, no tracking
• ✅ Consumer links expire in 24 hours (Microsoft's standard behaviour, not a limitation)

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Screenshots

Home	All Releases

Product detail — language selector	Product detail — download links

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CLI Tool

msdl is a standalone command-line tool that fetches Windows ISO links directly from your machine — no browser, no server in the middle.

# Interactive — pick product and language
msdl

# Direct with flags
msdl --id 3262 --lang "English"

# Evaluation / Server ISOs
msdl --eval server-2025

# Pipe directly into a downloader
msdl --id 3262 --lang "English" | wget -i -
msdl --id 3262 --lang "English" | xargs aria2c -x 16 -s 16

# List all available products
msdl --list

Install

Download the latest binary from GitHub Releases and rename it:

Platform	File	Rename to
Windows	msdl-windows-amd64.exe	msdl.exe
macOS (Apple Silicon)	msdl-darwin-arm64	msdl
macOS (Intel)	msdl-darwin-amd64	msdl
Linux	msdl-linux-amd64	msdl

winget support is in progress: winget install starkSV.msdl (pending package review).

Crowdsourced cache

By default, each successful fetch is contributed back to the web app's cache — so the next visitor gets a cached link instead of hitting Microsoft cold. Contribution is a background POST to /contribute. No personal data is sent — only the product ID, SKU ID, and the raw Microsoft JSON response. To opt out:

msdl --id 3262 --lang "English" --no-contribute
# or: MSDL_NO_CONTRIBUTE=1

Usage telemetry

By default, each run sends an anonymous event to help us understand which products are popular and which platforms are used. No personal data is sent — only action type (fetch, eval, list, interactive), platform (windows, darwin, linux), CLI version, and whether the run succeeded. To opt out:

MSDL_NO_TELEMETRY=1 msdl --id 3262 --lang "English"

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Project Structure

windows-iso-downloader/
├── frontend/            # React 19 + TypeScript + Vite + Tailwind v4
├── backend/             # Go proxy server (recommended for production)
├── cli/                 # Go CLI — direct ISO fetching from user's machine
├── cloudflare-worker/   # Optional CF Worker for distributed IP routing
└── README.md

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How It Works

Browser → Backend → (CF Worker) → Microsoft API → Signed CDN URL
              ↓
         Cache check (hit → return immediately, no Microsoft call)
              ↓ miss
          1. Register session (Microsoft tracking endpoint)
          2. Parse MDT fingerprint script
          3. Fetch SKU list (available languages)
          4. Fetch signed CDN download URL
          5. Cache result → return to browser

The flow mirrors Fido.ps1 by Pete Batard — the same script bundled with Rufus.

Outbound requests to Microsoft are optionally routed through a Cloudflare Worker (cloudflare-worker/worker.js). This distributes requests across Cloudflare's global edge IPs instead of a single server IP, preventing Microsoft's rate-limit block (error 715-123130) under high traffic. The Worker is opt-in via environment variables — omit them to go direct to Microsoft.

Caching layer

The backend uses a four-layer in-memory cache to reduce Microsoft API calls from thousands per day to ~50–100, preventing the 715-123130 rate-limit block under real traffic.

Cache	Key	TTL	Purpose
SKU cache	product_id	7 days	Language lists are stable; no need to hit Microsoft on every page load
Link cache	product_id:sku_id	Dynamic (parsed from se param in the signed URL, minus 30 min buffer)	Signed CDN URLs are not IP-bound — safe to serve the same link to all users
Eval cache	slug	24 hours	Eval Center fwlink redirects change rarely
Negative cache	product_id or product_id:sku_id	60 seconds	Prevents thundering-herd retries during a rate-limit block

Additional resilience mechanisms:

• Singleflight (golang.org/x/sync/singleflight) — collapses concurrent cache misses into a single Microsoft fetch. 500 simultaneous misses → 1 outbound call.
• Stale-on-failure — if a cache refresh fails (rate-limited or transient error), the expired entry is served temporarily while a background refresh is attempted through singleflight.
• Jitter — ±5 min random offset on TTLs prevents synchronized mass-expiry spikes.
• Cache eviction — a background goroutine evicts expired entries every 30 minutes.

All caches are in-memory and reset on restart. If REDIS_URL is set, a Redis/Valkey L2 cache supplements the in-memory layer: on startup the in-memory cache is seeded from Redis (restart-safe), and every fresh Microsoft fetch is written through to Redis. If Redis is unavailable the backend falls back to memory-only mode silently. Monitor the cache via the /metrics endpoint.

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Running Locally

Backend (Go)

cd backend
go run main.go
# Runs on http://localhost:3002

Frontend

cd frontend
npm install
npm run dev
# Runs on http://localhost:5173

Create frontend/.env.local:

VITE_API_URL=http://localhost:3002

Optional: Cloudflare Worker (recommended for production)

Deploy cloudflare-worker/worker.js to Cloudflare Workers, then set these on the backend:

CF_WORKER_URL=https://your-worker.your-name.workers.dev
CF_WORKER_SECRET=your-secret   # must match the CF_WORKER_SECRET secret set in the Worker's settings
METRICS_SECRET=your-metrics-secret  # enables the /metrics endpoint; omit to disable it

Omit CF_WORKER_URL / CF_WORKER_SECRET to go direct to Microsoft (fine for local development and low-traffic self-hosting).

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API Reference

GET /skuinfo?product_id=<id>

Returns available languages for a product.

{
  "Skus": [
    {
      "Id": "0x0409",
      "Language": "en-US",
      "LocalizedLanguage": "English (United States)"
    }
  ]
}

GET /proxy?product_id=<id>&sku_id=<sku>

Returns signed download links from Microsoft's CDN.

{
  "ProductDownloadOptions": [
    {
      "Uri": "https://software.download.prss.microsoft.com/...",
      "Architecture": "x64"
    }
  ]
}

GET /evallinks?product=<slug>

Returns direct CDN links for evaluation ISOs (Server/Enterprise). Links are resolved from Microsoft's Eval Center fwlink redirects and cached for 24 hours.

Valid slugs: server-2025, server-2022, server-2019, server-2016, win11-ent

{
  "links": [
    { "arch": "x64", "lang": "en-us", "url": "https://software-static.download.prss.microsoft.com/..." },
    { "arch": "x64", "lang": "fr-fr", "url": "https://software-static.download.prss.microsoft.com/..." }
  ]
}

POST /contribute

Accepts a crowdsourced link from the CLI tool to warm the cache. Requires Authorization: Bearer <CONTRIBUTE_SECRET> header.

{
  "product_id": "3262",
  "sku_id": "0x0409",
  "response": { /* raw Microsoft JSON */ }
}

Returns 200 OK on acceptance, 400 on validation failure (expired link, unknown product), 429 on rate limit (~5 req/min per IP).

GET /metrics?secret=<secret>

Returns real-time cache statistics for the running instance. Auth via ?secret= query param or Authorization: Bearer <secret> header. Requires METRICS_SECRET env var to be set.

{
  "sku":  { "requests": 42, "cache_hits": 39, "ms_fetches": 3, "neg_hits": 0, "hit_rate": "92.9%", "cache_size": 8 },
  "link": { "requests": 38, "cache_hits": 35, "ms_fetches": 3, "neg_hits": 0, "stale": 0, "hit_rate": "92.1%", "cache_size": 6 },
  "eval": { "requests": 12, "cache_hits": 12, "stale": 0, "hit_rate": "100.0%", "cache_size": 5 },
  "neg_cache_size": 0,
  "total_ms_fetches": 6
}

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Supported Products

Consumer releases

Product	ID	Architecture
Windows 11 25H2	3262	x64
Windows 11 25H2	3265	ARM64
Windows 11 25H2 (updated)	3321	x64
Windows 11 25H2 (updated)	3324	ARM64
Windows 11 24H2	3113	x64
Windows 11 24H2	3131	ARM64
Windows 10 22H2	2618	x64 / x86
Windows 10 22H2 Home China	2378	x64
Windows 8.1	52	x64 / x86
Windows 8.1 Single Language	48	x64 / x86

Evaluation editions (Server & Enterprise)

180-day trial ISOs sourced directly from Microsoft's Eval Center CDN. No registration required.

Product	Slug	Architecture
Windows Server 2025	server-2025	x64
Windows Server 2022	server-2022	x64
Windows Server 2019	server-2019	x64
Windows Server 2016	server-2016	x64
Windows 11 Enterprise	win11-ent	x64

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Tech Stack

Frontend (frontend/)

Framework	React 19 + TypeScript
Build tool	Vite 8
Styling	Tailwind CSS v4
Animation	Motion (Framer Motion v12)
UI primitives	Radix UI
Toast	Sonner
Font	Geist
Router	React Router v7

Backend (backend/)

Language	Go 1.25+
HTTP	net/http (stdlib, no framework)
Caching	4-layer in-memory · sync.RWMutex · dynamic TTL · Redis/Valkey L2
Concurrency	golang.org/x/sync/singleflight
UUID	github.com/google/uuid
MDT parsing	regexp (stdlib)
Redis client	github.com/redis/go-redis/v9

CLI (cli/)

Language	Go 1.25+
Interactive UI	github.com/charmbracelet/huh
HTTP	net/http (stdlib)
Releases	GitHub Actions · cross-compiled for Windows / macOS / Linux

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Deployment

Recommended setup:

Component	Platform
Frontend	Cloudflare Pages / Vercel (static)
Backend	VPS (Hetzner, DigitalOcean, Linode, etc.)
Outbound proxy	Cloudflare Worker (optional, recommended for public instances)

⚠️ Deploy the Go backend to a standard VPS, not serverless platforms. The Cloudflare Worker is used only as an outbound proxy for Microsoft API calls — the backend itself must be a long-running process with session state.

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Contributing

Pull requests welcome — see CONTRIBUTING.md for dev setup, how to add products/eval editions, and PR conventions.

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Disclaimer

This project is not affiliated with, endorsed by, or sponsored by Microsoft Corporation. Windows is a registered trademark of Microsoft Corporation. All ISO files are served directly from Microsoft's official CDN — this project does not host any files.

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License

MIT © TechLatest