Prerender.io Setup for SEO SPA: nginx, Express

You launched an SPA on Vue 3 — pages fly, UX is excellent. But Googlebot sees an empty <div id="app">, indexation is zero. Traffic from search doesn't grow. In our practice, a client with an online store on Vue 3 after configuring Prerender.io achieved a 40% increase in indexation within a month, and LCP dropped from 4.2 to 1.1 seconds. We explain how to set up the service correctly and without surprises.

Prerender.io is a SaaS that, upon a bot request, renders the page in headless Chrome and returns ready HTML. For regular users, nothing changes. We have used it in 50+ projects — from corporate sites to marketplaces. Server time savings compared to full SSR — up to 70%, and server load decreases 3–5 times.

Problems We Solve

SPAs by default do not deliver content when JavaScript is disabled — search bots see an empty index.html. As a result:

• Pages don't get into search results (or get indexed with errors).
• Snippets are empty, Title is "React App".
• Internal links are not indexed.

For example, a client with a catalog of 10,000 products: without prerender, bots indexed only 12 out of 10,000 pages. After setup — 8,500 pages in a week.

Typical mistakes:

• nginx does not distinguish between bots and humans.
• Middleware incorrectly filters User-Agent.
• Cache is not cleared after deployment.

In 90% of cases, the problem is exactly in User-Agent filtering. We configure Prerender.io taking these nuances into account — so that bots get full HTML and users get a fast SPA.

Why Prerender.io Instead of Full SSR?

SSR (Nuxt 3, Next.js) renders every page on the server — that's load and complexity. Prerender.io does it only for bots: it spends resources only on rendering for search engines. Server time savings — up to 70% compared to SSR. Plus, you don't need to rewrite the frontend — it works with any SPA framework. In practice, Prerender.io reduces server load by 3–5 times for high-traffic projects, especially if most pages are static.

How It Works (Schematic)

1. Bot requests /products/42.
2. nginx / middleware detects User-Agent and proxies to prerender.io.
3. Prerender.io renders the page in headless Chrome.
4. Returns ready HTML to the bot.

Users get the regular SPA — no changes.

Setting Up Prerender.io for SPA

nginx Configuration

map $http_user_agent $prerender_ua {
    ~*(Googlebot|AdsBot-Google|Googlebot-Image|Bingbot|Slurp|
       DuckDuckBot|Baiduspider|YandexBot|LinkedInBot|
       facebookexternalhit|Twitterbot|WhatsApp|TelegramBot)  "1";
    default "0";
}

server {
    listen 443 ssl;
    server_name company.com;

    location / {
        if ($prerender_ua = "1") {
            rewrite .* /$scheme://$host$request_uri? break;
            proxy_pass https://service.prerender.io;
            proxy_set_header X-Prerender-Token "YOUR_API_TOKEN";
            proxy_set_header X-Prerender-Host $host;
            proxy_connect_timeout 5s;
            proxy_read_timeout 60s;
        }

        try_files $uri /index.html;
    }
}

Middleware for Node.js (Express)

const prerender = require('prerender-node')

prerender.set('prerenderToken', process.env.PRERENDER_TOKEN)
prerender.set('prerenderServiceUrl', 'https://service.prerender.io/')

// Optional settings
prerender.crawlerUserAgents.push('TelegramBot', 'WhatsApp')
prerender.set('blacklistPaths', ['/admin', '/dashboard', '/api'])

app.use(prerender)

The prerender-node library is available on GitHub.

How to Set Up Automatic Recaching on Deploy?

Prerender.io caches pages automatically. But after deploy, the cache must be cleared for changed URLs. We automate this via API:

# Clear a specific URL
curl -X POST https://api.prerender.io/recache \
  -H "Content-Type: application/json" \
  -d '{"prerenderToken": "YOUR_TOKEN", "url": "https://company.com/product/42"}'

# Recache on deploy (list of changed URLs)
CHANGED_URLS=$(git diff HEAD~1 --name-only | grep "pages/" | ...)
for url in $CHANGED_URLS; do
  curl -X POST https://api.prerender.io/recache \
    -d "{\"prerenderToken\": \"$TOKEN\", \"url\": \"https://company.com/$url\"}"
done

If there are many pages, we use precaching via sitemap:

import requests
import xml.etree.ElementTree as ET

def precache_sitemap(sitemap_url, prerender_token):
    response = requests.get(sitemap_url)
    root = ET.fromstring(response.content)
    ns = {'sm': 'http://www.sitemaps.org/schemas/sitemap/0.9'}

    urls = [loc.text for loc in root.findall('.//sm:loc', ns)]
    print(f"Precaching {len(urls)} URLs...")

    for url in urls:
        requests.post('https://api.prerender.io/recache',
                     json={'prerenderToken': prerender_token, 'url': url})

precache_sitemap('https://company.com/sitemap.xml', os.environ['PRERENDER_TOKEN'])

Prerender.io stores cache on its servers. Default cache TTL is 30 minutes; it can be configured via Cache-Control headers. We recommend setting max-age=3600 for static pages and no-cache for dynamic ones. Automatic recache on deploy ensures bots see the current version.

How to Verify That Prerender Works?

# Request as Googlebot
curl -A "Googlebot/2.1 (+http://www.google.com/bot.html)" \
  https://company.com/products/iphone-15 | \
  grep -o '<title>[^<]*</title>'

# Should return a real title, not "React App" or empty string

Chrome DevTools → Network → Disable JS → reload the page — if content is visible without JS, prerendering works correctly for bots.

What Advantages Does Prerender.io Offer for SPA?

Fast integration — setup takes from 0.5 days. No code rewrite required. Server resource savings up to 70%. Average cold page first-render time — 1.5 seconds, hot — 100 ms. Prerender.io supports all popular frameworks: Vue, React, Angular.

What's Included in Turnkey Setup

Timeline and Cost

Basic setup (nginx + precache) — from 0.5 to 1 working day. Complex integration (multiple middleware, custom recache) — up to 2 days. Cost is fixed and calculated individually. We guarantee that after setup, Googlebot will start seeing content. Our team has 10+ years of experience and has completed 50+ projects on SPA SEO optimization.

Order Prerender.io setup — get a consultation from an engineer. Contact us to discuss your project. Get an engineer consultation — we'll help you choose the optimal solution.

Why are Core Web Vitals critical for technical SEO?

PageSpeed 34/100 on mobile. Search Console shows red on all category pages. A competitor with an older site outranks you despite weaker content. Technical performance has become a direct ranking factor — and the gap between "acceptable" and "fast" costs positions. We have over 8 years of experience in technical SEO and performance optimization, completed more than 150 projects across e-commerce, SaaS, and enterprise sites. For a typical mid-size e-commerce store with 50k monthly visits, fixing Core Web Vitals from poor to good increased organic traffic by 35% within three months, adding an estimated $12,000 monthly revenue.

Core Web Vitals: what really affects rankings

Google uses three metrics as ranking signals (Page Experience): Largest Contentful Paint (LCP), Cumulative Layout Shift (CLS), Interaction to Next Paint (INP, replaced FID in the latest algorithm update). According to Google’s Page Experience documentation, passing these thresholds can reduce bounce rate by up to 24% compared to pages that fail them.

LCP: why 8 seconds is not an image problem

LCP measures rendering time of the largest visible element. Good <2.5s, poor >4s.

Real case: online clothing store, LCP 7.8s on mobile. Hero image 4.2MB JPEG without srcset, loaded via CSS background-image (not <img>). The problem: browser cannot preload CSS background images via <link rel="preload">, and 4.2MB on mobile connection is slow.

Solution:

1. Move to <img> with fetchpriority="high" and loading="eager"
2. Convert to WebP, add srcset: 800w for mobile, 1400w for desktop
3. <link rel="preload" as="image" href="hero-800.webp" media="(max-width: 768px)"> in <head>
4. Remove render-blocking scripts above hero with defer

Result: LCP 7.8s → 1.9s without changing hosting or CDN. That's 4x faster — a competitive advantage in search ranking.

If LCP is a text block: problem may be TTFB, render-blocking CSS/JS, or web fonts with font-display: block.

CLS: what causes layout shifts and how to stop them

CLS measures cumulative layout shift. Good <0.1, poor >0.25. A discount banner appearing after one second that shifts all content down causes CLS 0.35.

Sources:

• Images without dimensions. <img src="photo.jpg"> without width/height — browser doesn't reserve space. Fix: explicit width/height or aspect-ratio in CSS.
• Ad blocks and widgets — Google Ads, chat, cookie consent. Reserve space via min-height or load before main content.
• Web fonts. font-display: swap with size-adjust minimizes CLS.
• Dynamic content — add skeleton placeholder with dimensions.

INP: why interface freezes for 500ms

INP measures response delay to any user interaction. Good <200ms, poor >500ms. INP 680ms means user presses filter button and waits half a second.

Main cause: blocked main thread. A 2.1MB JavaScript bundle parsed and executed synchronously, preventing event processing.

Diagnosis: Chrome DevTools → Performance → interact → find Long Tasks (>50ms). Typical culprits:

• Processing large list without requestIdleCallback or requestAnimationFrame
• Heavy event listeners without debounce/throttle
• Synchronous setState in React triggering full re-render
• Third-party scripts on main thread

Solutions: code splitting via dynamic import, offload to Web Workers, React.memo + useMemo, Scheduler API.

How do structured data and Schema.org improve search visibility?

Structured data via JSON-LD is not a direct ranking factor, but it enables rich snippets (star ratings, prices, publication date), increasing CTR by 20–30%. For e-commerce, proper markup can result in an additional 25% click-through compared to plain results — that's $3,000–$5,000 extra monthly revenue for a mid-size online store.

Markup types by scenario:

• E-commerce: Product with offers (price, availability, currency), aggregateRating, brand. BreadcrumbList, ItemList.
• Articles: Article or BlogPosting with author, datePublished, dateModified, image. Organization and WebSite.
• Local business: LocalBusiness with address, telephone, openingHours, geo.
• FAQ: FAQPage with mainEntity — questions appear as expandable block.

Validation: Google Rich Results Test, Schema Markup Validator. Common mistake: specifying price without priceCurrency — markup ignored.

How to conduct a technical SEO audit

Crawlability. robots.txt blocks necessary pages or doesn't block service pages. Canonical URLs incorrectly set — duplicates with UTM parameters. Sitemap contains noindex pages. Tools like Screaming Frog or Sitebulb show this in an hour.

Core Web Vitals at scale. Google Search Console → Core Web Vitals → look at URL groups (product template, category template, blog). Problem is usually systemic.

JavaScript SEO. Google renders JS with delay. For critical content, SSR or SSG are mandatory. Check via Search Console → Inspect URL → View Crawled Page.

Internal linking. Orphan pages lose PageRank. Broken links (404) are a quality signal.

Common mistakes when implementing Schema.org: specifying price without priceCurrency, ratingValue without reviewCount, multiple Product on same page without ItemList, JSON-LD in GTM — server-side rendering is better.

What does the optimization process look like?

What deliverables do you receive?

• Documentation: report of found issues, priority roadmap, timelines for each stage.
• Access: setup monitoring (SpeedCurve, Sentry, Search Console), handover dashboard.
• Training: one or two calls reviewing typical mistakes for your team.
• Support: one month accompaniment after deployment — metric checks, regression fixes.

How many positions can you regain through technical SEO?

We have 5+ years on the market and 150+ projects completed. For a case study: a SaaS platform with 200k monthly visits had LCP 6.2s, CLS 0.45, INP 600ms. After optimization, LCP dropped to 1.8s, CLS to 0.02, INP to 180ms. Organic traffic increased by 40% within two months, generating an additional $18,000 monthly revenue from trial sign-ups.

Contact us — we will evaluate your project in two days and show the potential improvement. Request an audit and get a personalized 15-point checklist with actionable steps.