Substack Post Comments API

Endpoint

GET /v1/substack/post/comments

Parameters

url

Post URL, e.g. https://www.lennysnewsletter.com/p/all-of-the-lenny-and-friends-summit (max 500 characters). Provide url, post_id, or publication and slug.

post_id

Numeric post ID, as returned in post_id. Provide url, post_id, or publication and slug.

publication

Publication subdomain, host or URL, used together with slug.

slug

Post URL slug, e.g. all-of-the-lenny-and-friends-summit, used together with publication.

sort_by

Sort order: relevance (best first), most_recent, oldest (default: relevance)

get_sentiment

Set to true to add AI emotion analysis (Plutchik's Wheel) to each result. Adds +$0.001 per request to the cost. Returns emotion scores, dominant emotion, intensity, and polarity.

Response fields

comments

Top-level comments in the requested order

comment_id

Comment ID

body

Comment text

date

Date and time posted (UTC)

author

Commenter's handle

author_name

Commenter's display name

author_id

Commenter's user ID

author_url

Link to the commenter's profile

likes

Number of likes

replies

Number of replies

restacks

Number of restacks

is_author

Whether the commenter wrote the post

is_pinned

Whether the comment is pinned

author_pic_url

Author's profile picture URL

reactions

Reaction counts by emoji

liked_by

Names of the first people who liked the comment

status

published, or Substack's removal status

url

Direct link to the comment

children

Replies, each with the same fields (nested to any depth)

sentiment

Emotion analysis results. Only present when get_sentiment=true. Returns null if analysis fails.

emotions

Plutchik emotion scores (0-100) for: joy, trust, fear, surprise, sadness, disgust, anger, anticipation.

dominant_emotion

The emotion with the highest score.

emotional_intensity

Overall emotional intensity on a scale of 0-10.

polarity

Overall sentiment polarity: positive, negative, or neutral.

post_id

The post's ID

post_url

The post's URL

sort_by

The sort order used

total

The post's comment count

count

Number of comments returned, including nested replies

truncated

True when a very large thread was cut at the response size limit (whole top-level comments are dropped from the end)

Example Request

curl "https://apidirect.io/v1/substack/post/comments?url=https%3A%2F%2Fwww.lennysnewsletter.com%2Fp%2Fhow-duolingo-reignited-user-growth"   -H "X-API-Key: YOUR_API_KEY"

import requests

response = requests.get(
    "https://apidirect.io/v1/substack/post/comments",
    headers={"X-API-Key": "YOUR_API_KEY"},
    params={"url": "https://www.lennysnewsletter.com/p/how-duolingo-reignited-user-growth"}
)
print(response.json())

Example Response

{
  "comments": [
    {
      "author": "fullstackresearcher",
      "author_id": "8067246",
      "author_name": "Daniel Kyne",
      "author_pic_url": "https://bucketeer-e05bbc84-baa3-437e-9518-adb32be77984.s3.amazonaws.com/public/images/69f08c0f-8d66-4b63-8d88-97af005d6bab_2126x2126.png",
      "author_url": "https://substack.com/@fullstackresearcher",
      "body": "Nothing beats real life examples (especially including failures) in deep detail like this! 🙏",
      "children": [
        {
          "author": "jorgemazal1",
          "author_id": "25411757",
          "author_name": "Jorge Mazal",
          "author_url": "https://substack.com/@jorgemazal1",
          "body": "Thank you Daniel!",
          "children": [],
          "comment_id": "13190378",
          "date": "2023-02-28 21:45:14",
          "is_author": true,
          "is_pinned": false,
          "likes": 5,
          "replies": 0,
          "restacks": 0,
          "url": "https://www.lennysnewsletter.com/p/how-duolingo-reignited-user-growth/comment/13190378"
        }
      ],
      "comment_id": "13180393",
      "date": "2023-02-28 16:40:12",
      "is_author": false,
      "is_pinned": false,
      "liked_by": [
        "Lenny Rachitsky"
      ],
      "likes": 49,
      "reactions": {
        "❤": 49
      },
      "replies": 1,
      "restacks": 0,
      "status": "published",
      "url": "https://www.lennysnewsletter.com/p/how-duolingo-reignited-user-growth/comment/13180393"
    }
  ],
  "count": 79,
  "post_id": "104096876",
  "post_url": "https://www.lennysnewsletter.com/p/how-duolingo-reignited-user-growth",
  "sort_by": "relevance",
  "total": 78,
  "truncated": false
}

Frequently asked questions

Is the thread paginated?

No. One request returns the whole thread Substack serves, so there is no pages parameter.

Why is comments empty when total is not?

Comments on posts restricted to paying subscribers are hidden from non-subscribers. total still reports the count.

Does sentiment cover nested replies?

get_sentiment analyses the top-level comments. Nested replies under children are returned without sentiment.

Can a thread be too big?

Threads of a few thousand comments can exceed the 4MB response limit. In that case the response keeps as many whole top-level comments as fit and sets truncated to true.

How does pricing work?

You only pay for successful requests. The Substack Post Comments API costs $0.003 per request. There are no monthly fees or commitments. You get 50 free requests per endpoint every month.

Do I need a credit card to start?

No. You can sign up and use the free tier (50 requests/endpoint/month) without adding a payment method. You only need to add a card when you want to exceed the free tier.

Are there rate limits?

Yes, there's a concurrency limit of 10 simultaneous requests per endpoint per user. If you need more, just get in touch.