Your HTML.
Ridiculously fast.

<style>
  .contact-form {
    display: grid;
    gap: 12px;
    padding: 24px;
    border-radius: 12px;
  }
</style>

<form class="contact-form"
      action="https://api.pathline.io/submit"
      method="POST">
  <input type="hidden" name="access_key"
         value="YOUR-ACCESS-KEY">
  <input type="text" name="name" required>
  <input type="email" name="email" required>
  <textarea name="message"></textarea>
  <button type="submit">Send</button>
</form>

const form = document.querySelector('#contact-form');

form.addEventListener('submit', async (e) => {
  e.preventDefault();

  const res = await fetch('https://api.pathline.io/submit', {
    method: 'POST',
    body: new FormData(form),
  });

  const json = await res.json();
  if (json.success) {
    window.location.href = '/thank-you';
  }
});

'use client';

export function ContactForm() {
  async function handleSubmit(e) {
    e.preventDefault();

    const res = await fetch('https://api.pathline.io/submit', {
      method: 'POST',
      body: new FormData(e.currentTarget),
    });

    const json = await res.json();
    if (json.success) {
      window.location.href = '/thank-you';
    }
  }

  return (
    <form onSubmit={handleSubmit}>
      <input type="hidden" name="access_key"
             value="YOUR-ACCESS-KEY" />
      <input type="text" name="name" required />
      <input type="email" name="email" required />
      <textarea name="message" />
      <button type="submit">Send</button>
    </form>
  );
}