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OG Images in Vue & Nuxt

Generate OG images in Vue and Nuxt with the FastOG API — with a Dynamic API subscription (create your API key in the dashboard), subscription-based, HMAC-secured. This guide shows you how to create a signer utility for HMAC-signed OG image URLs and render dynamic Open Graph images on the fly. Preview with the Free OG Image Tester before you ship.

Quick Start

1. Create the signer utility

javascript

// lib/og-image-signer.js
import crypto from "crypto";

export function generateSignedOgUrl(params, options = {}) {
    const {
        baseUrl = "https://fastog.com/api/v1/og",
        apiKey = process.env.FASTOG_API_KEY,
        hmacSecret = process.env.FASTOG_HMAC_SECRET,
    } = options;

    if (!apiKey || !hmacSecret) {
        throw new Error("Missing FASTOG_API_KEY or FASTOG_HMAC_SECRET");
    }

    // RFC-3986 percent-encoding: keep A-Za-z0-9-._~
    const enc = (s) =>
        encodeURIComponent(s).replace(
            /[!'()*]/g,
            (c) => "%" + c.charCodeAt(0).toString(16).toUpperCase(),
        );

    // Every query param except the signature, INCLUDING key
    const all = { ...params, key: apiKey };

    // Canonical query: sorted enc(key)=enc(value) pairs joined with &
    const pairs = [];
    for (const [k, v] of Object.entries(all)) {
        for (const vv of Array.isArray(v) ? v : [v]) {
            pairs.push(`${enc(k)}=${enc(vv)}`);
        }
    }
    pairs.sort();
    const canonical = pairs.join("&");

    // Sign the exact bytes the server will verify
    const signature = crypto
        .createHmac("sha256", hmacSecret)
        .update(`GET/api/v1/og\n${canonical}`)
        .digest("hex");

    // Build the URL from the same pairs so bytes match the canonical form
    const url = new URL(baseUrl);
    for (const [k, v] of Object.entries(all)) {
        for (const vv of Array.isArray(v) ? v : [v]) {
            url.searchParams.append(Array.isArray(v) ? `${k}[]` : k, vv);
        }
    }
    url.searchParams.set("s", signature);

    return url.toString();
}

2. Environment variables

bash

# .env
FASTOG_API_KEY=sk_your_full_api_key_here
FASTOG_HMAC_SECRET=your_64_char_hex_secret_here

Nuxt 3

Page with useHead

vue

<!-- pages/blog/[slug].vue -->
<script setup>
const route = useRoute();
const { data: post } = await useAsyncData("post", () =>
    getPost(route.params.slug),
);

const { data: ogImageUrl } = await useAsyncData("og-image", () =>
    $fetch("/api/og", {
        query: {
            title: post.value.title,
            template: "blog",
            subtitle: post.value.excerpt,
        },
    }).then((res) => res.ogImageUrl),
);

useHead({
    title: post.value.title,
    meta: [
        { property: "og:image", content: ogImageUrl.value },
        { property: "og:title", content: post.value.title },
        { property: "og:description", content: post.value.excerpt },
    ],
});
</script>

<template>
    <article>
        <h1>{{ post.title }}</h1>
        <p>{{ post.excerpt }}</p>
    </article>
</template>

Server API Route

javascript

// server/api/og.get.js
import { generateSignedOgUrl } from "~/lib/og-image-signer";

export default defineEventHandler(async (event) => {
    const query = getQuery(event);
    const { title, template = "default", ...params } = query;

    if (!title) {
        throw createError({ statusCode: 400, message: "Missing title" });
    }

    const ogImageUrl = generateSignedOgUrl({
        template,
        title,
        ...params,
    });

    return { ogImageUrl };
});

Vue 3 (SPA)

Composable

javascript

// composables/useOgImage.js
import { ref, watch } from "vue";

export function useOgImage(params) {
    const ogImageUrl = ref(null);

    watch(
        () => params,
        async (newParams) => {
            try {
                const searchParams = new URLSearchParams(newParams);
                const res = await fetch(`/api/og?${searchParams}`);
                const data = await res.json();
                ogImageUrl.value = data.ogImageUrl;
            } catch (err) {
                console.error("Failed to generate OG image:", err);
            }
        },
        { immediate: true },
    );

    return ogImageUrl;
}

Component

vue

<!-- components/BlogPost.vue -->
<script setup>
import { useOgImage } from "~/composables/useOgImage";

const props = defineProps({
    post: Object,
});

const ogImageUrl = useOgImage({
    title: props.post.title,
    template: "blog",
    subtitle: props.post.excerpt,
});
</script>

<template>
    <article>
        <h1>{{ post.title }}</h1>
        <p>{{ post.excerpt }}</p>
    </article>
</template>

Backend API (Express)

javascript

// server/index.js
import express from "express";
import crypto from "crypto";

const app = express();

app.get("/api/og", (req, res) => {
    const { title, template = "default", ...params } = req.query;

    if (!title) {
        return res.status(400).json({ error: "Missing title" });
    }

    const apiKey = process.env.FASTOG_API_KEY;
    const hmacSecret = process.env.FASTOG_HMAC_SECRET;

    const enc = (s) =>
        encodeURIComponent(s).replace(
            /[!'()*]/g,
            (c) => "%" + c.charCodeAt(0).toString(16).toUpperCase(),
        );

    const all = { template, title, ...params, key: apiKey };

    const pairs = [];
    for (const [k, v] of Object.entries(all)) {
        for (const vv of Array.isArray(v) ? v : [v]) {
            pairs.push(`${enc(k)}=${enc(vv)}`);
        }
    }
    pairs.sort();
    const canonical = pairs.join("&");

    const signature = crypto
        .createHmac("sha256", hmacSecret)
        .update(`GET/api/v1/og\n${canonical}`)
        .digest("hex");

    const url = new URL("https://fastog.com/api/v1/og");
    for (const [k, v] of Object.entries(all)) {
        for (const vv of Array.isArray(v) ? v : [v]) {
            url.searchParams.append(Array.isArray(v) ? `${k}[]` : k, vv);
        }
    }
    url.searchParams.set("s", signature);

    res.json({ ogImageUrl: url.toString() });
});

app.listen(3001, () => {
    console.log("API server running on port 3001");
});

E-commerce Example

vue

<!-- pages/products/[id].vue -->
<script setup>
const route = useRoute();
const { data: product } = await useAsyncData("product", () =>
    getProduct(route.params.id),
);

const { data: ogImageUrl } = await useAsyncData("og-image", () =>
    $fetch("/api/og", {
        query: {
            title: product.value.name,
            template: "ecommerce",
            price: product.value.price,
            image: product.value.image,
        },
    }).then((res) => res.ogImageUrl),
);

useHead({
    meta: [
        { property: "og:image", content: ogImageUrl.value },
        { property: "og:title", content: product.value.name },
    ],
});
</script>

<template>
    <main>
        <h1>{{ product.name }}</h1>
        <p>{{ product.price }}</p>
    </main>
</template>

User Profile (Blog Template)

FastOG has no profile template — use blog for a profile-style card, passing the user's name as title, bio as subtitle, and name as author.

vue

<!-- pages/users/[username].vue -->
<script setup>
const route = useRoute();
const { data: user } = await useAsyncData("user", () =>
    getUser(route.params.username),
);

const { data: ogImageUrl } = await useAsyncData("og-image", () =>
    $fetch("/api/og", {
        query: {
            title: `${user.value.name} - Profile`,
            template: "blog",
            subtitle: user.value.bio,
            author: user.value.name,
        },
    }).then((res) => res.ogImageUrl),
);

useHead({
    meta: [
        { property: "og:image", content: ogImageUrl.value },
        { property: "og:title", content: `${user.value.name} - Profile` },
    ],
});
</script>

Common Pitfalls

Client-side Signing

Never sign OG URLs in browser code.

❌ Wrong:

vue

<script setup>
import { generateSignedOgUrl } from "~/lib/og-image-signer";
// Runs in browser — secret exposed!
const ogUrl = generateSignedOgUrl({ title: post.title });
</script>

✅ Correct:

javascript

// server/api/og.get.js (runs on server only)
import { generateSignedOgUrl } from "~/lib/og-image-signer";
export default defineEventHandler((event) => {
    return { ogImageUrl: generateSignedOgUrl({ title: query.title }) };
});

Signing Different Bytes Than You Send

The signature covers GET/api/v1/og plus a newline plus the canonical query — the sorted enc(key)=enc(value) pairs of every param except s, including key. Build the final URL from those same encoded pairs, or the server returns 401 invalid_signature.

Full API Reference

React Tutorial
SvelteKit Tutorial
Astro Tutorial
JavaScript Tutorial
Quick Start
HMAC Signature Guide
API Reference
SDK
Agent Integration
Documentation
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Topic

OG Images in Vue & Nuxt

Quick Start

1. Create the signer utility

2. Environment variables

Nuxt 3

Page with useHead

Server API Route

Vue 3 (SPA)

Composable

Component

Backend API (Express)

E-commerce Example

User Profile (Blog Template)

Common Pitfalls

Client-side Signing

Signing Different Bytes Than You Send

Full API Reference

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