Vue quickstart

1. Create an account if you do not have one.
2. Go to Fraud Scoring API → Device trackers, create a tracker, and list the domains it may run on. Include localhost while you build.
3. Copy the publishable key. It starts pk_live_.

This key is meant to be visible in your bundle. It is domain-locked and can only send fingerprints: it cannot score, read your data, or work from a site you did not authorise. Your kdn_live_ secret key is the opposite, and passing one to createKaidn() throws where you wrote it rather than letting it ship to every visitor.

Skip to step 3 if you have a project already.

npm create vite@latest kaidn-vue-quickstart -- --template vue
cd kaidn-vue-quickstart
npm install

Run it and open http://localhost:5173, Vite's default.

npm run dev

A component to attach to. Create src/components/SignupForm.vue:

<script setup>
import { ref } from "vue";

defineProps({ isLoading: Boolean });
const emit = defineEmits(["submit"]);

const email = ref("");
const password = ref("");
</script>

<template>
  <form class="wrap" @submit.prevent="emit('submit', { email, password })">
    <h1>Create an account</h1>

    <label for="email">Email</label>
    <input id="email" v-model="email" type="email" required
           placeholder="you@example.com" />

    <label for="password">Password</label>
    <input id="password" v-model="password" type="password" required />

    <button type="submit" :disabled="isLoading">
      {{ isLoading ? "Checking…" : "Create account" }}
    </button>
  </form>
</template>

And enough CSS to see it. Append to src/style.css:

.wrap {
  max-width: 380px; min-height: 100vh; margin: 0 auto;
  display: flex; flex-direction: column; justify-content: center; gap: .5rem;
  padding: 1rem; text-align: left;
}

input { padding: .6rem; border: 1px solid #ccc; border-radius: 6px; font: inherit; }
label { font-size: .85rem; color: #555; }

button {
  margin-top: .75rem; padding: .7rem 1.2rem; font: inherit; cursor: pointer;
  background: #111; color: #fff; border: 0; border-radius: 6px;
}
button:disabled { opacity: .6; cursor: not-allowed; }

npm install @kaidn/vue

Install it once, where you create the app. The plugin holds configuration and collects nothing on its own, so it is safe on every page including the ones with no signup on them.

import { createApp } from "vue";
import { createKaidn } from "@kaidn/vue";
import App from "./App.vue";
import "./style.css";

const app = createApp(App);

app.use(createKaidn({ publishableKey: "pk_live_your_key_here" }));

app.mount("#app");

For production, use an environment variable. Vite exposes anything prefixed VITE_, so import.meta.env.VITE_KAIDN_PK keeps it out of your repository. It is not a secret, but a key you can rotate without a code change is worth having.

Why a plugin and not a configure() call

A module-level singleton is the obvious shortcut and it is wrong the moment you render on a server: one Node process serves many visitors, and the last configure() to run would win for all of them. app.use() scopes the configuration to one app instance, which is the unit SSR already creates per request.

The injection key is a Symbol, so nothing else that provides "kaidn" can quietly overwrite it.

useDeviceId() collects when you ask it to, not on mount. That puts the work at the moment somebody acts, which is when the signal is freshest, and keeps fingerprinting off pages that do not need it.

<script setup>
import { useDeviceId } from "@kaidn/vue";
import SignupForm from "./components/SignupForm.vue";

const { getDeviceId, isLoading } = useDeviceId();

async function handleSubmit({ email, password }) {
  // Never throws. A blocked script or an ad blocker returns null, and your
  // signup carries on with one signal fewer.
  const deviceId = await getDeviceId();

  await fetch("/api/signup", {
    method: "POST",
    headers: { "content-type": "application/json" },
    body: JSON.stringify({
      email: email.value,
      password: password.value,
      deviceId,          // your server scores THIS
    }),
  });
}
</script>

<template>
  <SignupForm :is-loading="isLoading" @submit="handleSubmit" />
</template>

The composable gives you four things:

• getDeviceId() collects and returns string | null. Never throws.
• deviceId is a ref holding the last id collected, or null before the first call.
• isLoading is a ref, true while a collection is in flight. Bind your button to it.
• error is a ref holding whatever went wrong last, for your logging rather than your user.

The three refs unwrap automatically in a template, so isLoading works as written above. In script you need .value.

Note what is not here: no verdict and no decision. The browser is an untrusted place to make one, so it never sees a score. It produces an id; your server produces the judgement.

A double-clicked button fingerprints once, not twice. The composable keeps one collection in flight at a time, so an impatient visitor costs you one beacon rather than two.

This is the step that turns a device id into fraud prevention. Everything before it collects; nothing before it decides.

Your /api/signup handler takes the id and passes it to /v1/score. Node, since you are already in a JavaScript project:

import { Kaidn } from "@kaidn/sdk";

// Your SECRET key. Server only, never the browser.
const kaidn = new Kaidn({ apiKey: process.env.KAIDN_API_KEY });

// Express, Fastify, Hono, a Next.js route handler: the call is the same.
app.post("/api/signup", async (req, res) => {
  let r;
  try {
    r = await kaidn.score({
      event: "signup",
      ip: req.ip,
      email: req.body.email,
      device_id: req.body.kaidn_device_id,   // the id the browser collected
    });
  } catch {
    // FAIL OPEN. An outage in your fraud vendor must never become an
    // outage in your signup form.
    return res.json({ ok: true });
  }

  if (r.verdict === "block") {
    // Do not name the signal. It teaches the next attempt.
    return res.status(403).json({ error: "We could not create that account." });
  }

  const user = await createUser(req.body);
  if (r.verdict === "review") await flagForReview(user.id, r.event_id, r.reason_text);

  res.json({ ok: true });
});

Three answers, and you decide what each one means. Kaidn never blocks anybody on your behalf.

npm run dev

Open http://localhost:5173, fill the form, submit, and look at the network tab. Your /api/signup request carries the id:

{ "email": "you@example.com", "deviceId": "8f1c2ae9d4b7c3e05a1f6b28d9074e3c" }

Turn ad blockers off on localhost while you test. Any fingerprinting script can be blocked by an extension, and when that happens you get nothing rather than a cautious answer. We measured what that does to a competitor and published the numbers. That is why the composable returns null instead of throwing, and why the device id is one signal in a score rather than the whole thing.