Houd vast. Geen plaatjes.

<form method="post" action="/contact">
  <!-- je velden -->
  <script src="https://netslim.nl/captcha.js" defer></script>
  <div class="netslim-captcha" data-sitekey="nsk_…"></div>
  <button>Versturen</button>
</form>

$r = file_get_contents("https://netslim.nl/api/captcha/siteverify", false, stream_context_create(["http" => [
  "method" => "POST",
  "header" => "Content-Type: application/x-www-form-urlencoded",
  "content" => http_build_query(["secret" => "nss_…", "token" => $_POST["netslim-captcha-token"], "remoteip" => $_SERVER["REMOTE_ADDR"]]),
]]));
if (!json_decode($r)->success) { http_response_code(403); exit; }

const r = await fetch("https://netslim.nl/api/captcha/siteverify", {
  method: "POST",
  body: new URLSearchParams({ secret: process.env.NETSLIM_SECRET, token: req.body["netslim-captcha-token"], remoteip: req.ip }),
});
if (!(await r.json()).success) return res.status(403).end();

r = requests.post("https://netslim.nl/api/captcha/siteverify", data={
    "secret": os.environ["NETSLIM_SECRET"],
    "token": request.form["netslim-captcha-token"],
    "remoteip": request.remote_addr,
}).json()
if not r["success"]:
    abort(403)

curl -X POST https://netslim.nl/api/captcha/siteverify \
  -d secret=nss_… -d token=… -d remoteip=203.0.113.7

{ "success": true, "score": 1 }