Slack Interactivity Payload: Real block_actions JSON and response_url Limits

When someone clicks a button, picks from a select menu or chooses a date in a Slack message, Slack sends your app a block_actions payload. App shortcuts send different payload types, shortcut and message_action, compared on our app shortcuts test. The control that was used is in actions[0], the current value of every input in the message is in state.values, and response_url lets you post back or replace the message without a token. On 1 October 2026 we posted a message with three controls from a throwaway app in Socket Mode, clicked each one in Slack web, and logged what arrived. Then we tested how long and how often response_url works: it took 5 posts and refused the 6th, and it worked until 29 minutes 50 seconds after the click and was expired at 30 minutes 10 seconds. A slash command's response_url behaved the same way in our slash command payload test.

The message we clicked

[
  {
    "type": "section",
    "text": {
      "type": "mrkdwn",
      "text": "*Deploy request #42*\nInteractivity test: click each control."
    }
  },
  {
    "type": "actions",
    "block_id": "deploy_actions",
    "elements": [
      {
        "type": "button",
        "action_id": "approve_btn",
        "text": {
          "type": "plain_text",
          "text": "Approve"
        },
        "style": "primary",
        "value": "deploy-42"
      },
      {
        "type": "static_select",
        "action_id": "env_select",
        "placeholder": {
          "type": "plain_text",
          "text": "Environment"
        },
        "options": [
          {
            "text": {
              "type": "plain_text",
              "text": "staging"
            },
            "value": "staging"
          },
          {
            "text": {
              "type": "plain_text",
              "text": "production"
            },
            "value": "production"
          }
        ]
      },
      {
        "type": "datepicker",
        "action_id": "deploy_date",
        "placeholder": {
          "type": "plain_text",
          "text": "Pick a date"
        }
      }
    ]
  }
]

You need Interactivity turned on in the app settings. Over HTTP, Slack POSTs to the Interactivity Request URL as a form field named payload. In Socket Mode, which we used, the same JSON comes over the WebSocket. Each click must be acknowledged within 3 seconds.

The block_actions payload, field by field

This is what arrived for the third click, the datepicker, after we had already picked "production" in the select. We shortened token, trigger_id, response_url and the copy of the message's blocks:

{
  "type": "block_actions",
  "user": {
    "id": "U0B7L4YK420",
    "username": "sieun",
    "name": "sieun",
    "team_id": "T0B7JBCDKC1"
  },
  "api_app_id": "A0C5WFLQ10S",
  "token": "<verification token, deprecated>",
  "container": {
    "type": "message",
    "message_ts": "1790839285.958459",
    "channel_id": "C0C5QDNUJ7M",
    "is_ephemeral": false
  },
  "trigger_id": "12200682638674...",
  "team": {
    "id": "T0B7JBCDKC1",
    "domain": "slack-0yr1948"
  },
  "enterprise": null,
  "is_enterprise_install": false,
  "channel": {
    "id": "C0C5QDNUJ7M",
    "name": "w2-lab-1001"
  },
  "message": {
    "type": "message",
    "ts": "1790839285.958459",
    "text": "Deploy request #42",
    "blocks": "[... the original blocks ...]",
    "user": "U0C5QDUGPV1",
    "bot_id": "B0C5WFWMXT4"
  },
  "state": {
    "values": {
      "deploy_actions": {
        "env_select": {
          "type": "static_select",
          "selected_option": {
            "text": {
              "type": "plain_text",
              "text": "production",
              "emoji": true
            },
            "value": "production"
          }
        },
        "deploy_date": {
          "type": "datepicker",
          "selected_date": "2026-10-08"
        }
      }
    }
  },
  "response_url": "https://hooks.slack.com/actions/T0B7JBCDKC1/...",
  "actions": [
    {
      "type": "datepicker",
      "action_id": "deploy_date",
      "block_id": "deploy_actions",
      "selected_date": "2026-10-08",
      "action_ts": "1790839338.194143"
    }
  ]
}

What each part is for:

The value sits in a different key for each control type. These are the three actions[0] objects we received:

{"action_id": "approve_btn", "block_id": "deploy_actions", "text": {"type": "plain_text", "text": "Approve", "emoji": true}, "value": "deploy-42", "style": "primary", "type": "button", "action_ts": "1790839301.388125"}
{"type": "static_select", "action_id": "env_select", "block_id": "deploy_actions", "selected_option": {"text": {"type": "plain_text", "text": "production", "emoji": true}, "value": "production"}, "placeholder": {"type": "plain_text", "text": "Environment", "emoji": true}, "action_ts": "1790839323.674158"}
{"type": "datepicker", "action_id": "deploy_date", "block_id": "deploy_actions", "selected_date": "2026-10-08", "action_ts": "1790839338.194143"}

A button sends its value. A static select sends selected_option. Multi selects, users_select and external_select send other keys, shown in our select menu test. A datepicker sends selected_date as YYYY-MM-DD. The first click, on the button, came with "state": {"values": {}} because nothing had been chosen yet. Read state.values when you need the whole form, and actions[0] when you only need the control that was clicked.

Replacing the message with response_url

To change the message after a click, POST JSON to response_url with replace_original: true:

import requests

requests.post(response_url, json={
    "replace_original": True,
    "text": "Deploy request #42 approved",
    "blocks": [{"type": "section", "text": {"type": "mrkdwn",
        "text": "*Deploy request #42*\n:white_check_mark: Approved by <@U0B7L4YK420> for *production* on 2026-10-08"}}],
}, timeout=10)

It returned HTTP 200 with {"ok":true} and the message changed in place, with the controls gone:

Without replace_original, the post is a new message; our count and time tests below used "response_type": "in_channel", so every post showed in the channel. Editing a message by ts with a token instead is covered in Slack chat.update, tested.

How often and how long response_url works

We posted seven times in a row to the response_url from the select click:

The 6th post got used_url. A failed post does not tell you which earlier post used up the URL, so count your uses: 5 per click in our test.

For time, we kept the response_url from the button click and posted to it later:

It worked at 1 minute and was already expired 1,801 seconds after the click, one second past 30 minutes. To find the edge we clicked a second button and posted to its response_url just before 30 minutes:

It still worked at 29 minutes 50 seconds and was expired at 30 minutes 10 seconds, so the limit is 30 minutes from the click, and the 5-use limit applies inside that window. After that, update the message with chat.update and a bot token.

A click your app does not answer

We stopped the app process and clicked a button. After a few seconds Slack put a warning icon next to the button, with no text and nothing else for the person to read:

When the app came back, that click was never delivered: Slack does not retry interactivity payloads the way it retries events. The same goes for a handler that answers after 3 seconds. Acknowledge first, then do the work. The Block Kit Builder is the quickest way to design the message before you wire the handler.