substack.post

stable Standard

Fetch a Substack post by slug.

GET /v1/substack/post

What you get#

One Substack record in Onekey's unified shape, in data. If the record does not exist you get a 404 not_found and are not charged.

What it costs#

Standard · 1 credit for a fresh fetch, charged only when it succeeds.
Free when served from cache (0.2 credit for a cached response over 100 KB).
Free if the request is invalid (never charged) or the source fails or reports not found (refunded).

Parameters#

Name	Type	Required	Default	What it is	Constraints
`pub`	string	yes	(required)	Allowlisted Substack publication host, e.g. www.astralcodexten.com	max 253 chars; must match `[a-z0-9.-]{3,253}`; trimmed, lowercased
`slug`	string	yes	(required)	Post slug	max 150 chars; must match `[a-z0-9][a-z0-9-]{0,150}`; trimmed, lowercased

Request#

curl "https://api.onekey.dev/v1/substack/post?pub=www.astralcodexten.com&slug=open-thread-435" \
  -H "x-api-key: YOUR_API_KEY"

Try it

Add your key to run this call right here. No key? Get one free. The key stays in this tab.

Recorded response#

A real Substack response, recorded and returned in Onekey's shape. Fields the platform does not provide are null.

json

{
  "success": true,
  "data": {
    "content": {
      "id": "199202126",
      "title": "Open Thread 435",
      "url": "https://www.astralcodexten.com/p/open-thread-435",
      "createdAt": "2026-05-25T16:11:06Z",
      "text": "This is the weekly visible open thread. Post about anything you want, ask random questions, whatever. ACX has an unofficial subreddit , Discord , and bulletin board , and in-person meetups around the world . Most content is free, some is subscriber only; you can subscribe here . Also: 1: Thanks to everyone who sent in a book review contest entry. I’ll have finalist voting up within a week or two. 2: 80,000 Hours, an effective altruist career advice organization, is publishing their book 80,000 Hours: How To Have A Fulfilling Career That Does Good . Along with talking about how to most effectively do good, it also discusses which careers are most likely to be automated by AI soonest (and I trust Ben to have high-quality thinking on this topic). Release date is tomorrow, but if you’re fast you can preorder today for special bonuses. 3: I filled out my early ballot for the California primary election (Alameda County); if you’re interested you can find my choices and explanations <a href=\"https://www.reddit.com/r/slatestarcodex/comments/1tmscam/my_california_primary"
    },
    "media": {
      "thumbnailUrl": "https://substack-post-media.s3.amazonaws.com/public/images/06d5d0d9-e87e-425d-8fdc-4572e693952c_1536x1024.png"
    },
    "engagement": {
      "likes": 59,
      "comments": 672
    },
    "author": {
      "id": "12009663",
      "displayName": "Scott Alexander",
      "username": "astralcodexten",
      "avatarUrl": "https://substackcdn.com/image/fetch/f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fbucketeer-e05bbc84-baa3-437e-9518-adb32be77984.s3.amazonaws.com%2Fpublic%2Fimages%2F7b500d22-1176-42ad-afaa-5d72bc36a809_44x44.png"
    },
    "ext": {
      "audience": "everyone",
      "wordCount": 167,
      "subtitle": "..."
    },
    "entity": {
      "slug": "open-thread-435"
    }
  },
  "metadata": {
    "platform": "substack",
    "endpoint": "post",
    "cached": false,
    "stale": false,
    "age_s": 0,
    "fetched_at": "2026-01-01T12:00:00+00:00",
    "credits_charged": 1,
    "request_id": "7f3a9c2e5b1d4c8fa2e6d0b9c4f18e37"
  },
  "error": null
}

Field mapping#

How this endpoint's source fields become Onekey's unified schema. Fields the source lacks come back as null.

Source path	Onekey field	Transform
`id`	`content.id`	`toString`
`title`	`content.title`	-
`canonical_url`	`content.url`	`safeUrl`
`post_date`	`content.createdAt`	`toIsoDate`
`cover_image`	`media.thumbnailUrl`	`safeUrl`
`reaction_count`	`engagement.likes`	`toNumber`
`comment_count`	`engagement.comments`	`toNumber`
`publishedBylines.0.id`	`author.id`	`toString`
`publishedBylines.0.name`	`author.displayName`	-
`publishedBylines.0.handle`	`author.username`	-
`publishedBylines.0.photo_url`	`author.avatarUrl`	`safeUrl`
`audience`	`ext.audience`	-
`slug`	`entity.slug`	-
`wordcount`	`ext.wordCount`	`toNumber`
`subtitle`	`ext.subtitle`	-
`body_html`	`content.text`	`stripHtml`

Caching and freshness#

Fresh for about 30 minutes. Repeat calls in that window are served from cache and are free.
Between 30 minutes and 6 hours the cached copy is still served instantly and marked stale: true while Onekey refreshes it in the background.
If the source is down when a refresh is needed, the last copy can be served for up to 1 day more (marked stale).
A "not found" is remembered for 5 minutes and is free.
The cache is shared across all customers, which is what keeps repeat calls cheap.

What can go wrong#

Status	Code	What to do
401	`unauthorized`	Check the `x-api-key` header.
402	`insufficient_credits`	Add credits; your balance must cover the price.
404	`not_found`	That record does not exist. Free; do not retry.
422	`invalid_params`	Fix the parameters using the table above. Free.
429	`rate_limited`	Wait `Retry-After` seconds, then retry.
502	`upstream_error`	The source failed. Refunded; retry with backoff.

See Errors for the full list and retry guidance.

Status: stable (verified against the live source).