Workflow Transactional EmailWorkflow Transactional Email

Attach a file from an order or customer metafield

Many apps save a file on the order or the customer: an invoice or packing slip PDF from an invoicing app, a certificate, a signed contract. Shopify stores it in a metafield, either as a file in your Shopify Files or as a link to the file. This app can attach that file to the email a Flow workflow sends, without you uploading or linking anything by hand.

How it works

  1. Another app (or you) writes the file, or a link to it, into a metafield of the order or customer. In your Shopify admin that is Settings > Custom data > Orders (or Customers): a definition of type File, URL, or a text field an app writes a link into.
  2. In an email layout you add an attachment and choose Metafield as its source, then pick that definition. The picker shows what each one holds: a file, a link, or a list of either.
  3. In Shopify Flow, the Send Transactional Email or Send Marketing Email step has an Order field and a Customer field. Flow fills them from the trigger, so a workflow started by Order created already knows which order.
  4. When the email is sent, the app reads that metafield on that order or customer, downloads the file (from your Shopify Files, or from the link), and attaches it. A list metafield attaches every entry.

The layout only names the metafield. The workflow says whose order or customer, so one layout serves every order.

The metafield holds Definition type What the app does
A Shopify file File, List of files Follows the reference to the file in your Files and downloads it
A link URL, List of URLs, or a text field Downloads the file from that link. Only https:// links work; a link that does not answer or points at something other than a PDF, image, CSV or text file fails the send with the reason

Either way the size is checked when the email is sent, not in the editor, so metafield attachments are not counted in the editor's attachment total.

Set it up

Rich text and HTML layouts

In the Attachments card at the bottom of the editor, click Add from metafield. Pick Order or Customer, then the definition. The row shows the definition's name, what it holds and its namespace.key; Change picks another one.

Visual layouts

Add an Attachment block (or open one) and switch its source to Metafield. Choose metafield opens the same picker.

The permission

The app is installed without any access to your store data. The first time you pick an order or customer metafield, the picker asks for permission to read that resource's metafields and the files they point to. Shopify shows its own consent dialog; after Update, the list of definitions loads.

You can review and withdraw every permission at any time on the app's Permissions page. Withdrawing one makes every email that attaches a file from such a metafield fail until it is granted again. What each permission reads, and what it does not, is on Permissions: what the app can read from your store.

File name

By default the attachment keeps the file's own name: the name in your Shopify Files, or the last part of the link. The File name field overrides it and supports Liquid, for example invoice-{{ variables.order_name }}.pdf. When a list metafield holds several entries, the second and following get -2, -3 appended to the override.

When the metafield is empty

The app that writes the file often runs a few seconds after the trigger, so at the moment the email step runs the metafield can still be empty. What happens then depends on the Optional checkbox of the attachment:

Optional Behaviour
Off (default) The email is not sent yet. The app tells Flow to retry the step, and Flow redelivers it a little later; the email goes out as soon as the file is there.
On The email is sent without this attachment.

Leave it off for an invoice that must be there. Turn it on for a file that only some orders have.

Requirements and limits

  • The Flow step needs its Order or Customer field set. Steps that were added before this release do not have the fields yet: delete the step in the Flow editor and add it again.
  • Files up to 10 MB each; PDF, images, CSV, plain text and calendar files. Videos and 3D models are skipped.
  • Links must start with https:// and answer without a login. A link that redirects to a non-https address, or into a private network, is refused.
  • Orders of the last 60 days. Shopify only lets apps read recent orders. For a workflow on an older order the send fails with a clear message.
  • Microsoft 365 rejects messages with more than 4 MB of attachments in total; see Attachments and images.

What you see in History

Every outcome is on the History page. A step without an order, a withdrawn permission, an order Shopify cannot find, a link that does not answer, or a file over the limit is recorded as Failed with the reason and what to change. An empty metafield with Optional off is not a failure: Flow shows the retries, and the send appears once the file is there. A Resend from History reads the same order or customer again.

Test it

Send test email in the layout editor has no order or customer to read from, so it sends without metafield attachments. To test the attachment, run the workflow in Flow on an order that already has the file, or use Run on a Flow test with such an order.