splitforms.com
LEAD CAPTURE · CONTACT FORM TEMPLATE

Dark Mode Contact Form (HTML + CSS)

A contact form that respects the visitor's OS dark-mode preference automatically. Pure CSS, no JavaScript theme switcher, no library — uses prefers-color-scheme media queries.

1,000/mo free·no card·works on any host
form.htmlhtml22 lines
01<form action="https://splitforms.com/api/submit" method="POST">
02 <input type="hidden" name="access_key" value="YOUR_ACCESS_KEY">
03 <input type="hidden" name="subject" value="New contact form submission">
04
05 <label for="name">Full name *</label>
06 <input id="name" type="text" name="name" placeholder="Jane Builder" required>
07 <label for="email">Email *</label>
08 <input id="email" type="email" name="email" placeholder="jane@example.com" required>
09 <label for="phone">Phone *</label>
10 <input id="phone" type="tel" name="phone" placeholder="+1 415 555 0142" required>
11 <label for="message">Message *</label>
12 <textarea id="message" name="message" placeholder="How can we help?" required></textarea>
13
14 <!-- honeypot — bots fill every field -->
15 <input type="checkbox" name="botcheck" style="display:none" tabindex="-1" autocomplete="off">
16
17 <button type="submit">Send</button>
18</form>
19
20<p style="margin-top:12px;font-size:11px;color:#888;text-align:right">
21 Powered by <a href="https://splitforms.com" style="color:#888;text-decoration:none" target="_blank" rel="noopener">splitforms</a>
22</p>
1,000
submissions / mo, free
4
fields, ready to ship
5
code outputs
60s
from copy to inbox
§ 01Why it mattersthe qualifying-fields argument

OS-level dark mode is the standard in 2026 — every modern browser supports prefers-color-scheme and most visitors have a preference set. A contact form that respects that preference looks polished without any JavaScript or theme-toggle UI. The trick is using CSS custom properties for color tokens and a single @media (prefers-color-scheme: dark) override.

Native OS dark mode, no JS, no theme library.
✦ at a glance
  • Basic contact form · 4 fields
  • HTML, JS, React, PHP, cURL outputs
  • One POST endpoint, no SDK
  • Honeypot + classifier, no CAPTCHA
§ 02Live previewinteractive · sandboxed · no key required

See exactly what your visitors see — and you’ll receive.

Left: the rendered form, fully interactive in a sandboxed iframe. Right: the email and dashboard view that lands the moment a visitor submits.

preview · contact-form-dark-modelocalhost:3000
✦ what you’ll see in your inbox

Every submission becomes an email plus a dashboard row. The fields below are the exact payload your form will send. Reply-to is wired to the visitor’s email so hitting reply goes back to them.

dashboard · new submission14ms · 200 OK
SUBJECT · New contact form submission
Full name
Maya Iyer
Email
maya@studio71.co
Phone
+1 415 555 0142
Message
Loved your last open house in Hayes — looking for similar with parking. Pre-approved through Wells Fargo.

Iframe is sandboxed — submit doesn’t actually fire. Get your access key to wire it up live.

§ 03Three steps3 steps · ~60 seconds

Generate, embed, receive.

Three actions stand between you and your first lead. None of them require a backend, a database, or a CAPTCHA library.

STEP 01GENERATE

Define color tokens

Set --bg, --ink, --line, --accent in :root. These are your light-mode values.

Create your form
key=sk_live_••••••••
STEP 02EMBED

Override for dark mode

Inside @media (prefers-color-scheme: dark), redefine the same tokens with dark-friendly values. Every color in your form references the tokens, so the whole thing flips.

snippethtml
<form action="https://splitforms.com/api/submit" method="POST">
  …
</form>
STEP 03RECEIVE

(Optional) Add a manual toggle

If you want a manual override, add a `data-theme` attribute on `<html>` and additional CSS selectors. Most sites don't need this — system preference is enough.

inbox · 1 newjust now
FROM contact@yoursite.com
New contact form submission
Maya Iyer maya@studio71.co
Loved your last open house in Hayes — looking for similar with parking. Pre-approved through Wells Fargo.
§ 04Copy & ship5 languages · same endpoint

Five outputs. One backend.

HTML by default. Click open the language you ship in — every variant POSTs to the same /api/submit endpoint.

01HTMLform.html22 lines
<form action="https://splitforms.com/api/submit" method="POST">
  <input type="hidden" name="access_key" value="YOUR_ACCESS_KEY">
  <input type="hidden" name="subject" value="New contact form submission">

  <label for="name">Full name *</label>
  <input id="name" type="text" name="name" placeholder="Jane Builder" required>
  <label for="email">Email *</label>
  <input id="email" type="email" name="email" placeholder="jane@example.com" required>
  <label for="phone">Phone *</label>
  <input id="phone" type="tel" name="phone" placeholder="+1 415 555 0142" required>
  <label for="message">Message *</label>
  <textarea id="message" name="message" placeholder="How can we help?" required></textarea>

  <!-- honeypot — bots fill every field -->
  <input type="checkbox" name="botcheck" style="display:none" tabindex="-1" autocomplete="off">

  <button type="submit">Send</button>
</form>

<p style="margin-top:12px;font-size:11px;color:#888;text-align:right">
  Powered by <a href="https://splitforms.com" style="color:#888;text-decoration:none" target="_blank" rel="noopener">splitforms</a>
</p>
02JavaScriptform.js38 lines
<form id="lf-form">
  <label for="name">Full name *</label>
  <input id="name" type="text" name="name" placeholder="Jane Builder" required>
  <label for="email">Email *</label>
  <input id="email" type="email" name="email" placeholder="jane@example.com" required>
  <label for="phone">Phone *</label>
  <input id="phone" type="tel" name="phone" placeholder="+1 415 555 0142" required>
  <label for="message">Message *</label>
  <textarea id="message" name="message" placeholder="How can we help?" required></textarea>
  <button type="submit">Send</button>
</form>

<p style="margin-top:12px;font-size:11px;color:#888;text-align:right">
  Powered by <a href="https://splitforms.com" style="color:#888;text-decoration:none" target="_blank" rel="noopener">splitforms</a>
</p>

<script>
  document.getElementById('lf-form').addEventListener('submit', async (e) => {
    e.preventDefault();
    const data = new FormData(e.target);
    data.set('access_key', 'YOUR_ACCESS_KEY');
    data.set('subject', 'New contact form submission');

    const res = await fetch('https://splitforms.com/api/submit', {
      method: 'POST',
      body: data,
      headers: { Accept: 'application/json' },
    });

    const json = await res.json();
    if (json.success) {
      e.target.reset();
      alert('Sent!');
    } else {
      alert('Error: ' + (json.message || 'Try again'));
    }
  });
</script>
03React / Next.jsForm.tsx53 lines
'use client';

import { useState, type FormEvent } from 'react';

export default function BasicForm() {
  const [status, setStatus] = useState<'idle' | 'sending' | 'sent' | 'error'>('idle');

  async function onSubmit(e: FormEvent<HTMLFormElement>) {
    e.preventDefault();
    setStatus('sending');

    const data = new FormData(e.currentTarget);
    data.set('access_key', 'YOUR_ACCESS_KEY');
    data.set('subject', 'New contact form submission');

    const res = await fetch('https://splitforms.com/api/submit', {
      method: 'POST',
      body: data,
      headers: { Accept: 'application/json' },
    });

    const json = await res.json();
    setStatus(json.success ? 'sent' : 'error');
    if (json.success) e.currentTarget.reset();
  }

  if (status === 'sent') return <p>Thanks — we&rsquo;ll be in touch.</p>;

  return (
    <>
    <form onSubmit={onSubmit}>
      <label htmlFor="name">Full name *</label>
      <input id="name" type="text" name="name" placeholder="Jane Builder" required />
      <label htmlFor="email">Email *</label>
      <input id="email" type="email" name="email" placeholder="jane@example.com" required />
      <label htmlFor="phone">Phone *</label>
      <input id="phone" type="tel" name="phone" placeholder="+1 415 555 0142" required />
      <label htmlFor="message">Message *</label>
      <textarea id="message" name="message" placeholder="How can we help?" required />

      <button type="submit" disabled={status === 'sending'}>
        {status === 'sending' ? 'Sending…' : 'Send'}
      </button>

      {status === 'error' && <p>Something went wrong. Try again.</p>}
    </form>

      <p style={{ marginTop: 12, fontSize: 11, color: '#888', textAlign: 'right' }}>
        Powered by <a href="https://splitforms.com" target="_blank" rel="noopener" style={{ color: '#888', textDecoration: 'none' }}>splitforms</a>
      </p>
    </>
  );
}
04PHPsubmit.php28 lines
<?php
// Drop into a PHP page. Receives a form POST and proxies it to splitforms.com.
// Useful when you want to add server-side validation or rate limiting.

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $allowed = ['name', 'email', 'phone', 'message'];
    $payload = ['access_key' => 'YOUR_ACCESS_KEY'];
    $payload['subject'] = 'New contact form submission';

    foreach ($allowed as $f) {
        if (isset($_POST[$f])) $payload[$f] = $_POST[$f];
    }

    $ch = curl_init('https://splitforms.com/api/submit');
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($payload));
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_HTTPHEADER, ['Accept: application/json']);
    $response = curl_exec($ch);
    $status   = curl_getinfo($ch, CURLINFO_HTTP_CODE);
    curl_close($ch);

    header('Content-Type: application/json');
    http_response_code($status);
    echo $response;
    exit;
}
?>
05cURLtest.sh8 lines
curl -X POST https://splitforms.com/api/submit \
  -H "Accept: application/json" \
  -d "access_key=YOUR_ACCESS_KEY" \
  -d "subject=New contact form submission" \
  -d "name=Jane Builder" \
  -d "email=jane@example.com" \
  -d "phone=+15555555555" \
  -d "message=Hello from cURL" 

Replace YOUR_ACCESS_KEY with the key from your dashboard. That’s the only edit.

§ 04bUse this template with…25 frameworks · same backend

One template. Every framework.

The same field set works on every framework splitforms supports. HTML, React, Next.js, Vue, Astro, Hugo, WordPress — same POST, same backend.

§ 06FAQ4 answered

Things people ask before they ship.

Direct answers, no marketing fluff. Missing one? Email hello@splitforms.com.

01Will the dark version work in older browsers?
prefers-color-scheme has been supported since 2018 (Chrome 76, Firefox 67, Safari 12.1). Older browsers see the light theme — which is the safe fallback.
02How do I support both system preference AND a manual toggle?
Use a data-theme="dark" attribute on <html> and write [data-theme="dark"] selectors. Default to system preference, override on user action. Persist the choice in localStorage.
03Does Tailwind support this pattern?
Yes — Tailwind ships a dark: variant. Either base it on system preference (darkMode: 'media' in config) or on a class (darkMode: 'class'). Both work with splitforms.
04What about accessibility for low-contrast issues?
Hit WCAG AA on both themes — at least 4.5:1 for body text, 3:1 for large text. Use a contrast checker on every color combination. Dark mode is where most accessibility bugs hide because designers test light-mode first.
✻ ✻ ✻

Ship your dark mode contact form (html + css) in 60 seconds.

1,000 free submissions per month. No credit card. Copy the snippet, paste your access key, watch leads land in your inbox.

Get free access key →Browse all 67 templates →
v0.1 · founders pricing locked in · early access open