The fastest way to post to Twitter/X, LinkedIn, Instagram, TikTok, Facebook, YouTube, Pinterest, Reddit, and Threads simultaneously is one authenticated POST request. Here's the exact workflow.

Step 1: Get your API key

After signing up and creating a profile, your API key is in Settings → API Keys. Each profile gets its own key — so client A and client B each have isolated credentials.

Step 2: Connect your platforms

From the Profiles dashboard, connect each platform via OAuth. Fanout manages the OAuth app credentials — you just click "Connect" and authorize your account. Takes about 30 seconds per platform.

Step 3: Make the API call

# Post to 4 platforms at once

curl -X POST https://fanout.digital/api/v1/post \

-H 'Authorization: Bearer YOUR_API_KEY' \

-H 'Content-Type: application/json' \

-d '{

"profileId": "your-profile-id",

"platforms": ["twitter", "linkedin", "instagram", "facebook"],

"post": "Excited to announce our new product launch! 🚀"

Step 4: Handle the response

The API returns a post ID and per-platform status:

{

"postId": "post_abc123",

"status": "processing",

"platforms": {

"twitter": { status: "posted", postId: "1234567890" }

"linkedin": { status: "posted", postId: "urn:li:share:abc" }

"instagram": { status: "processing" }

"facebook": { status: "posted", postId: "987654321_abc" }

}

Optional: schedule for later

Add a scheduledFor field to post at a specific time:

{

"profileId": "your-profile-id",

"platforms": ["twitter", "linkedin"],

"post": "Monday morning content drop 📅",

"scheduledFor": "2026-03-10T09:00:00Z"

}

Optional: AI-generated platform variants

Add "aiVariants": true and instead of one post going to all platforms, Claude generates platform-optimized variants — punchy for Twitter, professional for LinkedIn, hashtag-rich for Instagram.

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Post to Multiple Social Platforms with One API Call