---
title: Avoiding duplicate-content SEO with vercel.app URLs and custom domains
description: Discover why search engines may treat your vercel.app URL and custom domain as separate pages, and how to consolidate ranking signals and protect your SEO.
url: /kb/guide/avoiding-duplicate-content-with-vercel-app-urls
canonical_url: "https://vercel.com/kb/guide/avoiding-duplicate-content-with-vercel-app-urls"
last_updated: 2025-11-27
authors: Justin Vitale
related:
- /docs/deployments/preview-deployments
- /docs/custom-domains
- /docs/git
- /docs/vercel-firewall/vercel-waf/custom-rules
install_vercel_plugin: npx plugins add vercel/vercel-plugin
---
If your Production site is accessible at **both** `your-project.vercel.app` _and_ a custom domain (for example, `https://your-custom-domain.com`), search engines can treat those URLs as separate pages which can potentially affect your SEO performance.
Vercel [Preview deployments](https://vercel.com/docs/deployments/preview-deployments) are **not indexed by search engines** by default because the `**X-Robots-Tag**` HTTP header is set to `noindex` automatically by Vercel. However, if you're using a [custom domain](https://vercel.com/docs/custom-domains) that is assigned to a [non-Production branch](https://vercel.com/docs/git#production-branch), the header `X-Robots-Tag: noindex` will **not** be set.
This guide walks you through the three-step process Vercel recommends to ensure crawlers recognize **one** canonical version of each page, while still letting you (and your users) preview deployments on the `vercel.app` host.
### 1\. Declare a canonical URL in every page
Add a `` tag in the `` of every HTML page so that crawlers know which host (and scheme) is authoritative:
``
- Use the absolute HTTPS URL including any trailing slash or path segments.
- In frameworks like **Next.js** or **SvelteKit**, place this in your shared document/layout component so it’s injected automatically.
### 2\. Use the 'X-Robots-Tag' header to prevent the vercel.app host from being indexed
The `X-Robots-Tag: noindex` header tells search engines and crawlers to drop the page from their indexing entirely. This can be configured using `vercel.json` or using framework-level configurations (e.g. `next.config.js`) (preferred).
### 2.1 Default to a framework-level header
If your framework supports `headers()` (Next.js) or a similar API, use this by default as framework headers are merged **after** `vercel.json`:
`// next.config.js module.exports = { headers: async () => [{ source: '/:path*', has: [{ type: 'host', value: 'your-project.vercel.app' }], headers: [{ key: 'X-Robots-Tag', value: 'noindex' }] } ] };` ### 2.2 Fallback to vercel.json If your framework doesn't support implementing headers, or you prefer a simpler approach, you can set the tag in your `vercel.json` configuration instead: `{ "headers": [ { "source": "/(.*)", "has": [{ "type": "host", "value": "your-project.vercel.app" }], "headers": [{ "key": "X-Robots-Tag", "value": "noindex" }] } ] }` ### 3\. Redirect traffic from unwanted hostnames Even with the `X-Robots-Tag: noindex` header enabled, users could still visit your `vercel.app` URL directly. To handle this, create a **WAF Custom Rule** that issues an HTTP **Redirect** to the canonical domain: 1. Go to **Project → Firewall** in the Vercel Dashboard. 2. Click **Add Rule** → name it “Redirect to canonical”. 3. Configure the condition and action as above. 4. Click **Save Rule** – changes propagate globally without requiring a new deployment. Learn more about WAF Custom Rule configurations: [https://vercel.com/docs/vercel-firewall/vercel-waf/custom-rules](https://vercel.com/docs/vercel-firewall/vercel-waf/custom-rules)
### 4\. Putting it all together
Verify your changes:
**1\.** Perform a `curl` lookup for your project's `vercel.app` URL and confirm the response header:
`curl -I https://your-project.vercel.app`
`X-Robots-Tag: noindex` should be surfaced in the response.
- **X-Robots-Tag: noindex** → prevents `.vercel.app` pages from entering the index.
**2\.** Inspect the HTML source of your custom domain and confirm the canonical tag points to the same host.
- **Canonical tag** → tells search engines which URL to rank.
**3\.** Manually navigate to your project's `vercel.app` URL in a browser to verify your WAF redirect works as intended.
- **WAF Redirect** → ensures humans (and link equity) end up on the canonical host.
**4\.** Use Google Search Console’s **URL Inspection** tool to check your domain's indexing status: [https://support.google.com/webmasters/answer/9012289?hl=en](https://support.google.com/webmasters/answer/9012289?hl=en)
With these four layers in place, you’ll avoid duplicate-content penalties while retaining all the convenience of Vercel Preview Deployments and multiple domains.