Workflow WebhooksWorkflow Webhooks

How to connect Slack to Shopify Flow

Slack signs every request it sends to your app - slash commands, interactive messages and Events API deliveries - with your app's signing secret. Workflow Webhooks turns that call into a Shopify Flow trigger, so your store can react to it: tag a customer, add an order note, send an internal email, update a metafield - anything Shopify Flow can do.

This guide sets up the whole path - Slack sends, Workflow Webhooks receives and verifies, Shopify Flow acts - with Slack's HMAC signature checked on every request, so nothing but Slack can start your workflow.

What you can build

  • Let your team fire a Shopify Flow workflow from Slack with a slash command, without giving anyone admin access.
  • Approve something in Slack and have Flow tag the order or customer that was approved.
  • Turn a Slack shortcut into a store action - add a tag, send an email, update a metafield.

Typical events to send: a slash command such as /restock, a button press on an interactive message, an Events API event.

Before you begin

  • Workflow Webhooks installed on your Shopify store.
  • Shopify Flow installed, which is free from the Shopify App Store.
  • An account on Slack with permission to create webhooks.

Step 1 - Create the webhook in Workflow Webhooks

  1. Open Workflow Webhooks -> Webhooks -> Create webhook and give it a name you will recognise in Flow, such as Slack events.
  2. Under Authentication, choose HMAC.
  3. Under Signature provider, pick Slack. The app fills in the header, algorithm, signed payload and replay window for you - there is nothing else to configure.
  4. Leave the secret empty for now and Save. Copy the webhook URL shown on the page.

See Authentication for the other authentication modes, and Payload mapping and Flow variables for choosing which fields reach Flow.

Step 2 - Add the endpoint in Slack

In your Slack app configuration, add the URL as the Request URL for the slash command, interactivity or Events API, and copy the Signing Secret from Basic Information -> App Credentials.

How to find your Slack signing secret

Slack app Signing Secret (Basic Information -> App Credentials).

Slack's own documentation on webhook signatures has the exact wording and screenshots for your account.

Paste that secret into the webhook's Secret field in Workflow Webhooks and save. From that moment every Slack delivery is verified before it reaches Flow.

What this checks

What Value
Signature header X-Slack-Signature
Where the signature sits The header value, after the prefix v0=
What is signed v0:{timestamp}:{body}
Signature HMAC-SHA256, hex encoded
Timestamp The X-Slack-Request-Timestamp header, as Unix seconds
Replay protection Requests whose signed timestamp is more than 5 minutes away from now are rejected
The secret Used as plain text. Paste it exactly as the sender shows it

In the signed payload, {body} is the raw request body, byte for byte, and {timestamp} is the timestamp above.

A request that fails any of these is rejected with 401, is recorded in History and troubleshooting, and never starts a workflow.

Step 3 - Build the Shopify Flow workflow

  1. In Shopify Flow, create a workflow and choose the Workflow Webhooks trigger.
  2. Press Record events, then send a test event from Slack (or use Send test in Workflow Webhooks) so Flow learns the shape of your data.
  3. Every webhook you own fires the same Flow trigger, so add a first condition on the webhook id to keep this workflow to Slack only. The id is shown on the webhook page.
  4. Add your actions - tag a customer, add a note, send an internal email, update a metafield.

Step 4 - Test it end to end

Trigger a real event in Slack. In Workflow Webhooks -> History you should see the invocation with status Success. If the signature was wrong you get a failed entry with the reason instead, and Verifying signed webhooks explains the signature tester that shows you exactly which step failed.

The signature does not match▾

In this order: the secret (the most common cause - an extra space, or a key from the wrong environment), whether the sender is using a different endpoint's secret, and whether anything between Slack and the app rewrites the body. Signatures cover the raw bytes, so a proxy that re-formats JSON breaks them. The signature tester on the webhook page shows the exact text that was signed.

I get 401 on every request▾

Check that the webhook's authentication is set to HMAC with the Slack provider selected, that the secret is filled in, and that Slack is posting to the URL exactly as the app shows it, including the code at the end.

Nothing appears in History▾

The request never arrived. Re-check the URL in Slack, and look at Slack's own delivery log for the response it got. A 404 means a wrong or deleted webhook, a 429 means you are over your plan's invocation limit - see Plans and usage.

The workflow runs for the wrong events▾

Every webhook in your store fires the same Flow trigger. Add a condition on the webhook id as the first step of the workflow, or narrow the events you send from Slack.

Requests fail with "timestamp outside tolerance"▾

Slack signs a timestamp and the app rejects anything more than 5 minutes old. This is normally a clock problem on the sending side, or a delivery that Slack retried much later with the original timestamp. Retries from the same original request cannot pass; ask Slack to send a fresh event.