How to Add Address Autocomplete in Vue 3

What the API returns

The API wraps every response in a standard envelope. The address suggestions live in the Result field, which for autocomplete is a plain array of strings:

{
  "Id": "3f2504e0-4f89-11d3-9a0c-0305e82c3301",
  "Result": [
    "123 Main St APT 1, Andover, MA 01810-3816",
    "123 Main St APT 1, Delhi, NY 13753-1257",
    "123 Main St STE 1, Caldwell, ID 83605-5476",
    "123 Main St STE 1, Corinth, NY 12822-1010",
    "123 Main St STE 1, Delhi, NY 13753-1258"
  ],
  "ClientSessionId": null,
  "StatusCode": 200,
  "IsError": false,
  "Errors": []
}

Each suggestion includes the full street, the unit designation (APT, STE, UNIT), city, state code, and ZIP+4. The API handles abbreviations (St, Ave, Blvd) and directional prefixes (N, S, E, W) on the way in, and returns clean, standardized output. Your backend reads Result; your Vue component renders that array.

Get your API key

1. Sign up at sthan.io and subscribe to the free Address Autocomplete tier
2. Open your dashboard and create an API key
3. Copy the key - it looks like sthan_live_xxxxxxxxxxxxxxxx

You get the key immediately, with no approval queue. An API key is the simplest way to authenticate: your backend sends it as a Bearer token on every request. (If you prefer a short-lived token, there is a JWT flow covered later.)

Add a backend proxy

A Vue app is just static files in the browser, so it cannot safely hold a secret. There are two reasons the call must go through a server. First, the API does not enable CORS for browser requests, so a direct call from the component would be blocked. Second, and more important, putting your API key in client-side JavaScript would expose it to anyone who opens the network tab. A tiny Node server solves both:

// server.js  (Node 18+ has a global fetch)
import "dotenv/config";
import express from "express";

const app = express();
const API_BASE = "https://api.sthan.io";

app.get("/api/address/autocomplete", async (req, res) => {
  const query = (req.query.query || "").toString().trim();
  if (query.length < 3) return res.json([]);

  const upstream = await fetch(
    `${API_BASE}/AutoComplete/USA/Address/${encodeURIComponent(query)}`,
    { headers: { Authorization: `Bearer ${process.env.STHAN_API_KEY}` } }
  );
  if (!upstream.ok) return res.status(502).json([]);

  const body = await upstream.json();
  // The envelope wraps the data — suggestions are in Result
  res.json(body.Result ?? []);
});

app.listen(3000);

Store the key in a .env file (STHAN_API_KEY=sthan_live_...) and keep it out of version control. If you already use Next.js, a Node/Express server, or any other backend, you can add this route there instead of running a separate process.

Build the Vue component

The component uses the Composition API and a 250ms debounce. Debouncing matters: without it, "123 main st" fires eleven requests, one per keystroke. With the debounce, it fires one request after the user pauses:

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

const items = ref([]);
let timer;

function onInput(event) {
  const query = event.target.value.trim();
  clearTimeout(timer);

  if (query.length < 3) {
    items.value = [];
    return;
  }

  // Wait 250ms after the last keystroke before calling the server
  timer = setTimeout(async () => {
    const res = await fetch(
      `/api/address/autocomplete?query=${encodeURIComponent(query)}`);
    items.value = await res.json();
  }, 250);
}
</script>

<template>
  <div>
    <input
      type="text"
      autocomplete="off"
      placeholder="Start typing your address..."
      @input="onInput"
    />
    <ul>
      <li v-for="(address, i) in items" :key="i">{{ address }}</li>
    </ul>
  </div>
</template>

The component only ever talks to /api/address/autocomplete on your own origin. No key, no CORS, no third-party script. From here you can style the list, add keyboard navigation, and fill the form fields when a user clicks a suggestion.

Configure the Vite dev proxy

During development your Vue app runs on one port and the backend on another. Proxy /api to the backend so the component can use a relative URL with no CORS setup:

// vite.config.js
import { defineConfig } from "vite";
import vue from "@vitejs/plugin-vue";

export default defineConfig({
  plugins: [vue()],
  server: {
    proxy: {
      "/api": "http://localhost:3000",
    },
  },
});

In production, serve the built Vue files from the same server that hosts the proxy route, and the relative /api path keeps working unchanged.

Alternative: JWT authentication

An API key is the simplest option and is all most apps need. If your security policy prefers short-lived credentials, the platform also supports a 2-step JWT flow. In your backend, call GET /Auth/Token once with your profileName and profilePassword headers, receive a token valid for up to 60 minutes, then send that token as the Bearer value on subsequent calls:

let cached = { token: null, expires: 0 };

async function getToken() {
  if (cached.token && Date.now() < cached.expires - 30_000) {
    return cached.token;
  }

  const res = await fetch("https://api.sthan.io/Auth/Token", {
    headers: {
      profileName: process.env.STHAN_PROFILE_NAME,
      profilePassword: process.env.STHAN_PROFILE_PASSWORD,
    },
  });
  const body = await res.json();

  cached.token = body.Result.access_token;
  cached.expires = new Date(body.Result.expiration).getTime();
  return cached.token;
}

This still runs entirely on the backend - the Vue component never sees credentials of any kind. Everything else stays the same.

Handle errors

Two status codes are worth handling explicitly so a hiccup never crashes your form:

• 401 - The key or token was rejected. Check the value and, on the JWT flow, refresh and retry once.
• 429 - Rate limit reached. Back off and return what the user has typed so far rather than throwing.

// In the Vue component, never let a failed fetch break the input
try {
  const res = await fetch(
    `/api/address/autocomplete?query=${encodeURIComponent(query)}`);
  items.value = res.ok ? await res.json() : [];
} catch {
  items.value = [];
}

Returning an empty list on failure means a momentary hiccup shows no suggestions rather than a broken page. The user can still type the address by hand.

What's next: confirm the address is deliverable

Autocomplete gets the user to a clean, well-formed address fast. It does not, on its own, confirm that mail or a package will actually arrive there - a suggestion can be correctly formatted yet point at a unit that no longer accepts delivery.

The natural next step is to run the chosen address through the Address Verification API at the moment the user submits the form. It returns a Delivery Point Validation (DPV) result and a deliverable status, standardizes the address to standard postal format, and appends ZIP+4 and county. Add a second backend route that calls the verification endpoint - the same pattern you already built:

const upstream = await fetch(
  `https://api.sthan.io/v2/address-verification/usa/speculative/${encodeURIComponent(selected)}`,
  { headers: { Authorization: `Bearer ${process.env.STHAN_API_KEY}` } });
const { Result } = await upstream.json();
// Read Result.deliverableStatus and Result.dpvConfirmation

Address Verification has its own free tier of 100 requests/month, with paid plans from $12/month. Pairing autocomplete (volume, real-time, as the user types) with verification (one confirming call at submit) keeps your costs low and your delivery data clean. For React and Angular variants, see Address Autocomplete in React, Vue & Angular.