Platforms

YouTube

Upload videos to a YouTube channel with title, visibility, tags, thumbnail and an automatic first comment.

Overview

The youtube platform uploads one video per post to a YouTube channel with the YouTube Data API v3. The post content becomes the video description. You can set:

Title, visibility (public, unlisted, private), category and tags
Made-for-kids and altered/synthetic content disclosures
A custom thumbnail
A first comment posted automatically after the upload

Connect the account

In Integrations, choose YouTube and sign in with the Google account that owns the channel.

App setup (self-hosted)

In a Google Cloud project, enable YouTube Data API v3.
Create an OAuth client of type Web application with the redirect URI https://social-publish-kappa.vercel.app/api/integrations/youtube/callback (override with YOUTUBE_REDIRECT_URI).
Set GOOGLE_CLIENT_ID and GOOGLE_CLIENT_SECRET. The same client is used by Google Business Profile.

Scopes requested: youtube.upload, youtube.readonly, youtube.force-ssl (needed for the first comment). Access tokens are refreshed automatically.

Until your Google Cloud project passes Google's audit for the YouTube Data API, videos uploaded through it are forced to private by YouTube, whatever visibility you send.

Post types & media rules

Rule	Limit
Media	Exactly 1 video and nothing else
Description (`content`)	5,000 characters
Title	100 characters, no `<` or `>`; defaults to the first line of the content
Tags	Up to 50, each up to 100 characters, 500 characters in total
Thumbnail	JPEG or PNG, up to 2 MB; the channel must be verified for custom thumbnails
First comment	10,000 characters

The video is streamed from its URL to YouTube, so it must be publicly reachable (media library files are served as signed URLs automatically). Video size and duration limits are YouTube's own.

Options

Option	Type	Required	Default	Description
`title`	string	No		Video title. Max 100 characters, no < or >. Defaults to the first line of the caption.
`visibility`	`public` \	`unlisted` \	`private`	No
`categoryId`	`1` \	`2` \	`10` \	`15` \
`tags`	string[]	No		Tags. Comma-separated, 500 characters total.
`madeForKids`	boolean	No	`false`	Made for kids
`thumbnailUrl`	string (URL)	No		Thumbnail. Custom cover. JPEG/PNG, up to 2 MB. Your channel must be verified to set custom thumbnails.
`firstComment`	string	No		First comment. Auto-posted comment after the video goes live
`containsSyntheticMedia`	boolean	No	`false`	Contains AI-generated content. Disclose if the video includes realistic altered or synthetic media

Examples

cURLNode.jsPython

curl -X POST https://social-publish-api.onrender.com/v1/posts \
  -H "x-access-key: $RELAYCAST_API_KEY" \
  -H "content-type: application/json" \
  -d '{
    "content": "Full walkthrough of the new dashboard.\n\nChapters:\n0:00 Intro\n1:30 Scheduling",
    "media": [{ "url": "https://cdn.example.com/walkthrough.mp4", "type": "video" }],
    "targets": [{
      "accountId": "8a7b6c5d-4e3f-4a1b-9c8d-7e6f5a4b3c2d",
      "options": {
        "title": "Dashboard walkthrough (2026)",
        "visibility": "unlisted",
        "categoryId": "28",
        "tags": ["tutorial", "dashboard"],
        "thumbnailUrl": "https://cdn.example.com/walkthrough-thumb.jpg",
        "firstComment": "Questions? Ask below and we will reply."
      }
    }],
    "scheduledFor": "2026-11-07T16:00:00Z"
  }'

const res = await fetch("https://social-publish-api.onrender.com/v1/posts", {
  method: "POST",
  headers: {
    "x-access-key": process.env.RELAYCAST_API_KEY!,
    "content-type": "application/json",
  },
  body: JSON.stringify({
    content: "Full walkthrough of the new dashboard.\n\nChapters:\n0:00 Intro\n1:30 Scheduling",
    media: [{ url: "https://cdn.example.com/walkthrough.mp4", type: "video" }],
    targets: [
      {
        accountId: "8a7b6c5d-4e3f-4a1b-9c8d-7e6f5a4b3c2d",
        options: {
          title: "Dashboard walkthrough (2026)",
          visibility: "unlisted",
          categoryId: "28",
          tags: ["tutorial", "dashboard"],
          thumbnailUrl: "https://cdn.example.com/walkthrough-thumb.jpg",
          firstComment: "Questions? Ask below and we will reply.",
        },
      },
    ],
    scheduledFor: "2026-11-07T16:00:00Z",
  }),
});
const { data } = await res.json();

import os, requests

res = requests.post(
    "https://social-publish-api.onrender.com/v1/posts",
    headers={"x-access-key": os.environ["RELAYCAST_API_KEY"]},
    json={
        "content": "Full walkthrough of the new dashboard.\n\nChapters:\n0:00 Intro\n1:30 Scheduling",
        "media": [{"url": "https://cdn.example.com/walkthrough.mp4", "type": "video"}],
        "targets": [{
            "accountId": "8a7b6c5d-4e3f-4a1b-9c8d-7e6f5a4b3c2d",
            "options": {
                "title": "Dashboard walkthrough (2026)",
                "visibility": "unlisted",
                "categoryId": "28",
                "tags": ["tutorial", "dashboard"],
                "thumbnailUrl": "https://cdn.example.com/walkthrough-thumb.jpg",
                "firstComment": "Questions? Ask below and we will reply.",
            },
        }],
        "scheduledFor": "2026-11-07T16:00:00Z",
    },
)
data = res.json()["data"]

scheduledFor controls when Relaycast uploads the video. The video goes live with the chosen visibility as soon as the upload completes.

Analytics show views, likes and comments from the video's statistics. Likes and comments are missing when the channel hides likes or has comments disabled. YouTube's Data API does not report impressions or shares.

Comment moderation and replies are not supported; only the automatic firstComment is.

Limitations & common errors

Error	Cause
`YouTube needs exactly one video`	No video, several items, or an image attached.
`YouTube descriptions allow 5000 characters`	`content` is too long.
`Title cannot contain < or >`	Remove angle brackets from `title`.
`Tags must total 500 characters or less`	Shorten or remove tags.
Target fails: could not fetch video	The video URL is not publicly reachable.
Video is private despite `visibility: "public"`	The Google Cloud project hasn't passed YouTube's audit.
Thumbnail or first comment missing	These run after the upload and never fail the post. The thumbnail needs a verified channel; the first comment needs the `youtube.force-ssl` scope (reconnect accounts connected before it was added).
Account becomes `reconnect_required`	Google access was revoked or the refresh token expired.

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