How to Like and Comment on LinkedIn Posts via API: A Developer's Guide

Why Automate LinkedIn Engagement?

LinkedIn engagement — liking posts and leaving thoughtful comments — is one of the most effective ways to grow your professional network. But doing it manually at scale is time-consuming.

With the Postpost API, you can programmatically:

• React to posts with any of LinkedIn's 6 reaction types
• Comment on posts in your network
• Reply to existing comments (nested threads)
• Remove reactions and comments when needed

This guide walks you through every endpoint with working code examples.

Prerequisites

Before you start, you'll need:

1. A Postpost account with an API key (starts with sk_)
2. A LinkedIn account connected via the Postpost dashboard
3. Your LinkedIn platformId (find it via the List Connections endpoint)

Part 1: Reacting to LinkedIn Posts

LinkedIn supports 6 reaction types:

Add a Reaction

Endpoint: POST https://api.postpost.dev/api/v1/linkedin-reactions

JavaScript

const response = await fetch('https://api.postpost.dev/api/v1/linkedin-reactions', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'x-postpost-key': 'YOUR_API_KEY'
  },
  body: JSON.stringify({
    postedId: 'urn:li:ugcPost:7429953213384187904',
    reactionType: 'LIKE',
    platformId: 'linkedin-ABC123'
  })
});
const data = await response.json();
console.log(data);
// { success: true, reaction: { reactionType: “LIKE” } }

Python

import requests
response = requests.post(
‘https://api.postpost.dev/api/v1/linkedin-reactions’,
headers={
‘Content-Type’: ‘application/json’,
‘x-postpost-key’: ‘YOUR_API_KEY’
},
json={
‘postedId’: ‘urn:li:ugcPost:7429953213384187904’,
‘reactionType’: ‘LIKE’,
‘platformId’: ‘linkedin-ABC123’
}
)
print(response.json())

cURL

curl -X POST https://api.postpost.dev/api/v1/linkedin-reactions \
  -H "Content-Type: application/json" \
  -H "x-postpost-key: YOUR_API_KEY" \
  -d '{
    "postedId": "urn:li:ugcPost:7429953213384187904",
    "reactionType": "LIKE",
    "platformId": "linkedin-ABC123"
  }'

Remove a Reaction

To unlike or remove any reaction:

await fetch('https://api.postpost.dev/api/v1/linkedin-reactions', {
  method: 'DELETE',
  headers: {
    'Content-Type': 'application/json',
    'x-postpost-key': 'YOUR_API_KEY'
  },
  body: JSON.stringify({
    postedId: 'urn:li:ugcPost:7429953213384187904',
    platformId: 'linkedin-ABC123'
  })
});

Change a Reaction

LinkedIn allows only one reaction per post. To change it, remove the existing reaction first, then add the new one:

// Remove old reaction
await fetch('https://api.postpost.dev/api/v1/linkedin-reactions', {
  method: 'DELETE',
  headers: {
    'Content-Type': 'application/json',
    'x-postpost-key': 'YOUR_API_KEY'
  },
  body: JSON.stringify({
    postedId: 'urn:li:ugcPost:7429953213384187904',
    platformId: 'linkedin-ABC123'
  })
});
// Add new reaction
await fetch(‘https://api.postpost.dev/api/v1/linkedin-reactions’, {
method: ‘POST’,
headers: {
‘Content-Type’: ‘application/json’,
‘x-postpost-key’: ‘YOUR_API_KEY’
},
body: JSON.stringify({
postedId: ‘urn:li:ugcPost:7429953213384187904’,
reactionType: ‘INTEREST’,
platformId: ‘linkedin-ABC123’
})
});

Part 2: Commenting on LinkedIn Posts

Post a Comment

Endpoint: POST https://api.postpost.dev/api/v1/linkedin-comments

JavaScript

const response = await fetch('https://api.postpost.dev/api/v1/linkedin-comments', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'x-postpost-key': 'YOUR_API_KEY'
  },
  body: JSON.stringify({
    postedId: 'urn:li:ugcPost:7429953213384187904',
    message: 'Great insights! This is exactly what our team has been discussing.',
    platformId: 'linkedin-ABC123'
  })
});
const data = await response.json();
console.log(data);
// {
//   success: true,
//   comment: {
//     id: “7434695495614312448”,
//     commentUrn: “urn:li:comment:(urn:li:ugcPost:xxx,7434695495614312448)”,
//     message: { text: “Great insights! …” }
//   }
// }

Python

import requests
response = requests.post(
‘https://api.postpost.dev/api/v1/linkedin-comments’,
headers={
‘Content-Type’: ‘application/json’,
‘x-postpost-key’: ‘YOUR_API_KEY’
},
json={
‘postedId’: ‘urn:li:ugcPost:7429953213384187904’,
‘message’: ‘Great insights! This is exactly what our team has been discussing.’,
‘platformId’: ‘linkedin-ABC123’
}
)
print(response.json())

cURL

curl -X POST https://api.postpost.dev/api/v1/linkedin-comments \
  -H "Content-Type: application/json" \
  -H "x-postpost-key: YOUR_API_KEY" \
  -d '{
    "postedId": "urn:li:ugcPost:7429953213384187904",
    "message": "Great insights! This is exactly what our team has been discussing.",
    "platformId": "linkedin-ABC123"
  }'

Reply to a Comment

To create a threaded reply, add the parentComment parameter:

await fetch('https://api.postpost.dev/api/v1/linkedin-comments', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'x-postpost-key': 'YOUR_API_KEY'
  },
  body: JSON.stringify({
    postedId: 'urn:li:ugcPost:7429953213384187904',
    message: 'Totally agree with your point!',
    platformId: 'linkedin-ABC123',
    parentComment: 'urn:li:comment:(urn:li:ugcPost:xxx,7434695495614312448)'
  })
});

Delete a Comment

await fetch('https://api.postpost.dev/api/v1/linkedin-comments', {
  method: 'DELETE',
  headers: {
    'Content-Type': 'application/json',
    'x-postpost-key': 'YOUR_API_KEY'
  },
  body: JSON.stringify({
    postedId: 'urn:li:ugcPost:7429953213384187904',
    commentId: 'urn:li:comment:(urn:li:ugcPost:xxx,7434695495614312448)',
    platformId: 'linkedin-ABC123'
  })
});

Part 3: Getting the Post URN

The postedId parameter requires a LinkedIn URN — not the URL you see in your browser.

Important: LinkedIn URLs use urn:li:activity:xxx format, but the API requires urn:li:share:xxx or urn:li:ugcPost:xxx.

For posts you created via Postpost, retrieve the URN from the get-post endpoint:

const response = await fetch(
  'https://api.postpost.dev/api/v1/get-post/YOUR_POST_GROUP_ID',
  { headers: { 'x-postpost-key': 'YOUR_API_KEY' } }
);
const data = await response.json();
const linkedInUrn = data.posts[0].postedId;
// e.g., “urn:li:share:7434685316856377344”

Part 4: Putting It All Together

Here's a complete workflow that reacts to a post and leaves a comment:

const API_KEY = process.env.POSTPOST_API_KEY;
const PLATFORM_ID = 'linkedin-ABC123';
const BASE_URL = 'https://api.postpost.dev/api/v1';
async function engageWithPost(postUrn, reactionType, comment) {
const headers = {
‘Content-Type’: ‘application/json’,
‘x-postpost-key’: API_KEY
};
// Step 1: Add a reaction
const reactionRes = await fetch(${BASE_URL}/linkedin-reactions, {
method: ‘POST’,
headers,
body: JSON.stringify({
postedId: postUrn,
reactionType,
platformId: PLATFORM_ID
})
});
console.log(‘Reaction:’, (await reactionRes.json()).success);
// Step 2: Post a comment
const commentRes = await fetch(${BASE_URL}/linkedin-comments, {
method: ‘POST’,
headers,
body: JSON.stringify({
postedId: postUrn,
message: comment,
platformId: PLATFORM_ID
})
});
const commentData = await commentRes.json();
console.log(‘Comment ID:’, commentData.comment?.id);
return commentData;
}
// Usage
await engageWithPost(
‘urn:li:ugcPost:7429953213384187904’,
‘INTEREST’,
‘Excellent post! The data really backs up your thesis.’
);

Common Errors

Reaction	API Value	Icon
Like	LIKE	Thumbs up
Celebrate	PRAISE	Fire
Love	EMPATHY	Heart
Insightful	INTEREST	Lightbulb
Support	APPRECIATION	Clapping hands
Funny	ENTERTAINMENT	Laughing face

Error	Cause	Fix
"postedId is required"	Missing post URN	Include postedId in request body
"Invalid postedId"	Wrong URN format	Use urn:li:share:xxx or urn:li:ugcPost:xxx
"Invalid reactionType"	Typo in reaction	Use one of: LIKE, PRAISE, EMPATHY, INTEREST, APPRECIATION, ENTERTAINMENT
"LinkedIn connection not found"	Wrong platformId	Check your connections via List Connections
"Invalid API key"	Bad API key	Verify your key at postpost.dev/dashboard

Tips for LinkedIn Engagement at Scale

1. Add delays between requests — LinkedIn has rate limits. Add at least 1 second between API calls.
2. Use meaningful comments — Generic comments get flagged. Write substantive, relevant responses.
3. Mix reaction types — Don't just "like" everything. Use "Insightful" for thought leadership posts, "Celebrate" for announcements.
4. Track engagement with MCP — If you use Claude, Cursor, or another AI assistant, Postpost's MCP server lets you engage with LinkedIn posts conversationally.

Bonus: Use Claude Code or Cursor Instead of Writing Code

Don't want to write API calls? Postpost's MCP server lets you like, comment, and mention people on LinkedIn using plain English — directly from Claude Code or Cursor.

Step 1: Connect Postpost MCP to Claude Code

Run this single command in your terminal:

claude mcp add postpost --transport http https://mcp.postpost.dev --header "Authorization: Bearer sk_YOUR_API_KEY"

Or add it to your global config at ~/.claude.json:

{
  "mcpServers": {
    "postpost": {
      "type": "http",
      "url": "https://mcp.postpost.dev",
      "headers": {
        "Authorization": "Bearer sk_YOUR_API_KEY"
      }
    }
  }
}

Step 1 (alt): Connect Postpost MCP to Cursor

Create .cursor/mcp.json in your project root:

{
  "mcpServers": {
    "postpost": {
      "type": "http",
      "url": "https://mcp.postpost.dev",
      "headers": {
        "Authorization": "Bearer sk_YOUR_API_KEY"
      }
    }
  }
}

Restart Cursor, and Postpost's 18 tools will appear in the AI chat.

Step 2: Like and React to Posts in Natural Language

Once connected, just talk to Claude or Cursor's AI chat:

Step 3: Comment on Posts Conversationally

Step 4: Mention People and Companies

You can @mention LinkedIn members and companies in posts created via MCP. The mention syntax is @{urn:li:person:ID|Display Name} for people and @{urn:li:organization:ID|Company Name} for companies.

Important for mentions: The display name must exactly match the LinkedIn profile name (case-sensitive), including company suffixes like "Inc" or "LLC". If it doesn't match, the mention will render as plain text instead of a clickable link.

Why Use MCP Instead of Direct API Calls?

• No code required — just describe what you want in natural language
• Context-aware — Claude remembers previous posts, so you can say "reply to that comment" or "unlike that post"
• Multi-step workflows — "React with insightful and leave a comment" in a single message
• Works in your IDE — engage with LinkedIn without leaving Claude Code or Cursor
• 18 tools available — beyond reactions and comments, you can schedule posts, check analytics, manage connections, and more

What's Next?

• Full API Reference — All parameters and error codes
• LinkedIn Mentions Guide — Tag people and companies in posts
• MCP Integration — Use AI assistants to manage LinkedIn engagement
• LinkedIn Analytics — Track your engagement performance