# Formspree “Form not found” and other errors: fixes

Formspree says “Form not found”, “Form should POST”, “Invalid Referer header” or “This form isn't set up yet”? Each response reproduced, with the cause and fix.

Author: Formgong
Published: 2026-10-09
Language: en
Canonical: https://formgong.com/en/blog/formspree-errors/

“Form not found” means the ID after /f/ in your form's action is wrong or the form was deleted: copy the endpoint again from the Formspree dashboard. “Form should POST” means the form has no method="POST", so the browser opened the URL. “Invalid Referer header” and “This form isn't set up yet” come from the old formspree.io/your@email address format.

## Every response at a glance

Reproduced on 09.10.2026 with a made-up form ID. Formspree answers with an HTML page when a normal form submits, and with JSON when your code sends `Accept: application/json`, so the same mistake has two texts.

Formspree errors
What you seeHow you sent itCause

`{"error":"Form not found","errors":[{"code":"FORM_NOT_FOUND","message":"Form not found"}]}` (404)fetch with JSONWrong or deleted form ID
Page: “Form not found. Please check the form hashid”HTML formWrong or deleted form ID
Page: “Form should POST. Make sure your form has the method="POST" attribute”Link, or form without `method`The browser sent GET
`{"error":"Please submit POST request."}` (405)fetch with GETThe browser sent GET
`{"error":"Invalid \"Referer\" header"}` (400)Old `formspree.io/you@example.com` addressNo page address sent with the request
`{"error":"This form isn't set up yet"}` (404)Old `formspree.io/you@example.com` addressThat address has no form in Formspree

## “Form not found”: the form ID is wrong

Every Formspree form has an endpoint like `https://formspree.io/f/xxxxxxxx`. “Form not found” means the part after `/f/` does not match a form in any account. The usual causes:

- a typo, or the placeholder `YOUR_FORM_ID` left in the code by a tutorial or an AI builder;

- the form was deleted, or created in another Formspree account;

- an environment variable holds the ID locally but is empty on the live site, so the URL ends in `/f/undefined`.

Copy the endpoint again from the form's page in the Formspree dashboard and paste the whole URL into the form's `action`.

```html
<form action="https://formspree.io/f/YOUR_FORM_ID" method="POST">
  <label>Email <input type="email" name="email" required></label>
  <label>Message <textarea name="message" required></textarea></label>
  <button type="submit">Send</button>
</form>
```

## “Form should POST”: add method="POST"

An HTML form without `method` sends GET, which turns the fields into a URL and opens it. Formspree only accepts POST, so it shows “Form should POST”. The same page appears if you open the endpoint in a browser tab. Add `method="POST"` to the form; with fetch, set `method: "POST"`, or you get `{"error":"Please submit POST request."}`.

## “Invalid Referer header” and “This form isn't set up yet”

Old tutorials post to `https://formspree.io/you@example.com`. On that address Formspree answered with `Invalid "Referer" header` when the request carried no page address, and with `This form isn't set up yet` when it did. Either way, nothing is delivered. Create a form in Formspree and use its `/f/` endpoint instead of an email address.

## With fetch, read the answer before you show success

AI-built forms often post with fetch and show “Thanks!” whatever comes back. With a wrong ID, Formspree answers 404 and your visitor still sees the thank-you message. In our test of 105 AI-built sites, 27 forms showed success and sent nothing ([the study](/en/blog/contact-forms-that-send-nothing/)). Send `Accept: application/json`, check `response.ok`, and show Formspree's `error` text otherwise.

```javascript
const response = await fetch("https://formspree.io/f/YOUR_FORM_ID", {
  method: "POST",
  headers: { Accept: "application/json" },
  body: new FormData(form),
});
const data = await response.json();
if (!response.ok) throw new Error(data.error); // e.g. "Form not found"
showSuccess();
```

## If you are switching anyway

Formgong works the same way: a form posts to one URL with a key, and the answer says `"success": true` or explains what is wrong. It differs where it matters for small sites: Telegram alerts on the free plan, 300 submissions a month, data stored in the EU, and pages in 12 languages. See [Formgong vs Formspree](/en/vs/formspree/) and the [HTML guide](/en/docs/html/); switching means changing the `action` and adding `<input type="hidden" name="access_key">`. Our endpoint is `https://formgong.com/submit`.

## Frequently asked questions

### What does Formspree “Form not found” mean?

The ID after /f/ in your form's action does not match a form. Copy the endpoint again from the Formspree dashboard; check that the live site does not end in /f/undefined.

### Why does Formspree say “Form should POST”?

The form has no method="POST", or you opened the endpoint as a link. Add method="POST" to the form tag.

### Can I still use formspree.io/my@email.com?

On our test that address format returned “Invalid Referer header” or “This form isn't set up yet”. Create a form and use its /f/ endpoint.

### How do I know a Formspree form really sent?

With fetch, send Accept: application/json and show success only when response.ok is true. Then submit a test and look for it in the Formspree dashboard.

## Sources and documentation

- [Formspree: help center](https://help.formspree.io/)
- [MDN: the form method attribute](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/form#method)
- [MDN: Using the Fetch API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch)
- [HTML contact form](https://formgong.com/en/docs/html/)

[Get a form key](https://formgong.com/en/#top)