Post to Slack automatically

01

Connect Slack

1. Create a Slack app for your workspace (api.slack.com/apps → From scratch).
2. Turn on Incoming Webhooks and add one for the channel, or give a bot chat:write and files:write.
3. Paste the webhook URL or the bot token in the dashboard.

Posting for clients? Send them a connect link so they connect their own Slack account without a Reelspan login.

02

Get an API key

In the dashboard, open Developers → API keys and create one. Keep it in an environment variable such as REELSPAN_KEY; never in code you share.

03

Post with one request

Send the video as a file, or as a public URL like below. Add more platform[] fields to post the same thing everywhere at once.

curl -X POST https://api.reelspan.com/v1/posts/video \
  -H "Authorization: Bearer $REELSPAN_KEY" \
  -F user=my-brand \
  -F "platform[]=slack" \
  -F "video=https://example.com/clip.mp4" \
  -F "title=Your message"

const form = new FormData();
form.append('user', 'my-brand');
form.append('platform[]', 'slack');
form.append('video', 'https://example.com/clip.mp4');
form.append('title', 'Your message');

const res = await fetch('https://api.reelspan.com/v1/posts/video', {
  method: 'POST',
  headers: { Authorization: `Bearer ${process.env.REELSPAN_KEY}` },
  body: form,
});
console.log(await res.json());

import os, requests

res = requests.post(
    "https://api.reelspan.com/v1/posts/video",
    headers={"Authorization": f"Bearer {os.environ['REELSPAN_KEY']}"},
    files=[
        ("user", (None, "my-brand")),
        ("platform[]", (None, "slack")),
        ("video", (None, "https://example.com/clip.mp4")),
        ("title", (None, "Your message")),
    ],
)
print(res.json())

slack_title sets the text for Slack only, when it should differ from the other networks’.

04

Slack options

title

The message text, up to 40,000 characters.

• Messages go to the channels your own Slack app is in.
• Videos, photos and files are uploaded into the message.

Every field, with its limits: the docs.

05

Schedule it and check the result

• Add scheduled_date (ISO 8601) and timezone to post later, or add_to_queue=true to take the next slot of your posting schedule.
• The response has Slack’s status and the post’s link. For big files send async_upload=true and check GET /v1/posts/status?request_id=…, or get a signed webhook when it’s live.
• If Slack refuses a post, the error says why in plain words, and you can retry just that network.

06

Without code

• n8n, Make, Zapier or Airtable: the same request from a workflow.
• Claude, ChatGPT or any MCP client: ask “post this to Slack”.
• The dashboard: write once, check Slack’s limits as you type, post now or schedule.

07

Ideas

• Share every published post with your team channel.
• Send client approvals and reports to a shared channel.

More on Slack: what you can post there. Other networks: all upload guides.