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How to Connect Kit (formerly ConvertKit) to a WordPress Form?

Updated On : September 13, 2026By : Reading Time : 2 minutes

Key Takeaways

  • Nexter Blocks Pro adds each Form block submission to a Kit form and its automations when Action After Submit is set to ConvertKit.
  • Kit v3 API key is required, and a v4 API key does not work; the key is pasted into Custom API Key under the ConvertKit panel.
  • Each submission subscribes the email to the chosen Kit form, with the name saved as first name, and Kit form settings control whether email confirmation is required.
Table of Contents

Connecting your form to Kit, formerly ConvertKit, adds new subscribers to your Kit form and its automations.

The Form block in Nexter Blocks Pro subscribes each visitor to a Kit form you choose.

For every Form setting in one place, see the Form block guide.

LIVE BLOCK LINK

Before You Start

  • Edition: Pro — The ConvertKit action needs Nexter Blocks Pro.
  • Block to enable: Form, switched on under Nexter > Blocks in your WordPress dashboard.
  • Your Kit API key (v3): found under Settings > Developer in Kit. See Kit’s API overview.
  • A form in Kit: subscribers are added to a Kit form, so create one first.

Learn via Video Tutorial

Steps

  1. Add the Form block to your page, click Design from Scratch and choose Simple Contact Form or Newsletter Form.
  1. Select the Form block (not a field inside it). In Action After Submit, open Options and choose ConvertKit. You can keep Email selected as well.
The Action After Submit panel with Options
  1. Open the ConvertKit panel that appears and paste your key into Custom API Key.
The ConvertKit panel with the Custom API Key field
  1. When your Kit forms load, pick one in the ConvertKit Form dropdown.
  1. Save the page, then submit the form once on the front end to test the connection.

How It Behaves

  • Each submission subscribes the email to the Kit form you picked, with the name as first name.
  • Kit’s own form settings decide whether the subscriber must confirm by email.

Limitations

  • Pro only.
  • The block uses Kit’s v3 API key. A v4 API key does not work here.
  • Without a form chosen in ConvertKit Form, nothing is sent to Kit.

Troubleshooting

The ConvertKit Form dropdown does not appear

The key could not load your forms. Copy the v3 API key again and check you have at least one form in Kit.

Subscribers stay unconfirmed

Turn off double opt-in (incentive email) in the Kit form’s settings if you want them added straight away.

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Related Frequently Asked Questions

What do I need before connecting a WordPress form to Kit?

Nexter Blocks Pro is required because the ConvertKit action only works in Pro. The Form block also has to be enabled under Nexter > Blocks in your WordPress dashboard, and Kit needs a v3 API key from Settings > Developer. One more practical requirement matters: subscribers are added to a Kit form, so that form has to exist first or there is nowhere for the submissions to go.

How do I connect a WordPress form to a Kit form?

The connection happens through the Form block in Nexter Blocks Pro. Add the Form block, choose Simple Contact Form or Newsletter Form, then set Action After Submit to ConvertKit and paste the v3 key into Custom API Key. Once Kit forms load, pick the target form from the ConvertKit Form dropdown. That dropdown choice is the actual destination, so leaving it blank means nothing gets sent.

Why is the ConvertKit Form dropdown not showing up?

That usually means Kit could not load your forms. The page points to two common causes: the v3 API key was copied incorrectly, or there is no form created in Kit yet. Since Nexter Blocks Pro pulls available forms before it can show the dropdown, fixing the key and confirming at least one Kit form exists are the two checks that matter most.

Why are subscribers staying unconfirmed after form submission?

Kit controls confirmation through its own form settings, not through Nexter Blocks Pro. If double opt-in, also called incentive email, is turned on in the Kit form, subscribers will stay unconfirmed until they complete that email step. Turning that off adds them straight away, which is useful when you want immediate list growth instead of an extra confirmation barrier.

Does this work with a v4 Kit API key?

No. The integration uses Kit’s v3 API key only, and the page explicitly says a v4 API key does not work here. That detail matters because a valid-looking newer key can still fail to load forms in Nexter Blocks Pro. If the dropdown never appears, re-copying the v3 key is one of the first fixes to try.

What happens when someone submits the connected form?

Each submission adds the email to the Kit form you picked, and the name is sent as first name. That means the chosen Kit form is doing more than storing contacts because its own automations can run too. In practice, this makes the exact form selection important: if no ConvertKit Form is chosen, nothing is sent to Kit at all.

Last reviewed: September 14, 2026

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