ActionSlackUpdated May 2026

How do I post a file in Slack with a caption?

Short answer: Drop the "Slack → Send File with Message" action anywhere in your workflow, map the inputs from upstream nodes, and publish.

Use this action All 45 Slack actions

Inputs

The fields this action accepts.

Every field can be mapped from an upstream trigger, AI step, table row, or hard-coded literal.

Field	Type	Required	Description
Channel channel	string	Required	Slack channel ID (starts with C for public, G for private group, D for DM). Find via List Channels. Not the channel name with #.
File URL file_url	string	Required	Public URL of the file to upload.
Filename filename	string	Required	Filename to show in Slack.
Caption comment	string	Optional	Optional comment to post alongside the file.

Sample request

{
  "channel": "e.g. C0123456789",
  "file_url": "e.g. https://example.com/path",
  "filename": "{{trigger.filename}}",
  "comment": "{{trigger.comment}}"
}

Returns

{
  "ok": true,
  "raw": {},
  "file_id": "F0123ABC",
  "permalink": "https://..."
}

Use these fields in downstream nodes for routing, logging, or error handling.

Triggered by

Apps that pair well as the trigger for Send File with Message.

Any of these apps can fire this action as part of a workflow.

Gmail → Slack

1 Gmail triggers

Google Sheets → Slack

2 Google Sheets triggers

FAQ

Questions about Send File with Message.

What does the Send File with Message action do in Slack?

Uploads a file and posts a message that includes it. Use it for reports, screenshots, or any auto-generated artifact.

What inputs does Send File with Message require?

Required: Channel, File URL, Filename. Every input accepts a static value or a variable from any upstream node in your workflow.

Can I use dynamic inputs from earlier workflow nodes?

Yes. Any field on this action can pull values from upstream nodes, whether that's a form response, a trigger payload, an AI output, or a lookup result.

What happens if Slack returns an error?

The workflow pauses on the failed node, the error message is captured in the run log, and you can retry the run with one click. Auto-retry policies are configurable per workflow with exponential backoff up to 5 attempts.

Does Send File with Message support batch operations?

Yes. Run Send File with Message inside a Loop node to process arrays. Tiny Command handles Slack's rate limits automatically so you don't have to throttle manually.

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