What is JavaScript SEO?

JavaScript SEO is the practice of making sure search engines can index content that's built in the browser by JavaScript instead of being in the HTML response. Traditional server-rendered websites put content in the response directly, so there's nothing to solve. Modern JavaScript sites put content in a bundle that runs in the browser, which means crawlers don't see it unless they execute JavaScript - and most don't.

Why doesn't Google just execute JavaScript?

Google does, but in a second pass that can be days or weeks behind the first pass. Google's own documentation calls this the Web Rendering Service. Meanwhile, the first-pass crawler indexes your page as whatever the initial HTML says it is, which in a JavaScript-heavy site is usually nothing. Other crawlers (Bingbot, Yandex, the AI crawlers, social share bots) don't execute JavaScript at all.

What is dynamic rendering?

Dynamic rendering is Google's officially-endorsed pattern for fixing JavaScript SEO: detect bot user agents at the edge or at your server, and serve them a pre-rendered HTML version of your page while serving humans the normal JavaScript experience. Google documented this approach in 2018 and has repeatedly confirmed it's not cloaking. PageGlass is a dynamic-rendering service built on Cloudflare's edge network.

Is dynamic rendering the same as cloaking?

No. Cloaking is serving different content to bots than to humans in order to deceive the crawler about what the page actually contains. Dynamic rendering serves the same content, just rendered server-side for bots and client-side for humans. Google explicitly distinguishes between the two and says dynamic rendering is allowed under its guidelines.

Will moving to Next.js or Nuxt fix this?

Yes, if you use their server-side rendering modes (not their client-side modes). Next.js App Router with server components produces HTML on the server, and Nuxt 3 does the same. The catch is that adopting them means rewriting or restructuring your existing JavaScript app, which is a weeks-to-months investment. PageGlass gives you the same crawler-visibility outcome without the framework migration.

How does Google actually crawl JavaScript?

Google uses a two-pass process. The first pass is a normal HTTP crawler that reads whatever the server sends. The second pass is the Web Rendering Service, which takes the response from the first pass, runs the JavaScript in a headless Chromium instance, waits for the rendered DOM to stabilise, and then indexes the result. The problem is that the second pass is delayed, batched, and resource-constrained. Fresh content, content-heavy pages, and sites with many client-rendered routes routinely get left in the first-pass index with missing or incomplete data.

JavaScript SEO: get indexed in five minutes, no SSR migration

Modern JavaScript sites build content in the browser, not on the server. Googlebot captures the initial HTML (empty div, one bundle) and moves on. Your content exists; the crawler never sees it.

This is a known problem, and the fix is simpler than you think.

100+ bots supportedPre-rendered by PageGlassFive-minute setupBuilt on Cloudflare's edge

Paste your site's URL above to see what Googlebot and other crawlers actually see. Takes about ten seconds.

Don't want an external tool? We understand.

If your stack already has SSR or SSG wired in, great. Retrofitting it onto a client-rendered app means weeks of work - new data layer, hydration, edge cases in production. PageGlass gets you the same crawler outcome without touching your code.

Fix this in three steps

Run a free JavaScript scan. Confirm the bot visibility gap caused by client-side JavaScript rendering - the scan takes ten seconds and needs no signup. You get exactly what Googlebot, Bingbot, and the AI crawlers see when they hit your URLs today, side by side with what your users see.
Add one CNAME record. Point your JavaScript site's domain through PageGlass in your DNS provider. The change takes thirty seconds and is fully reversible. Zero code changes, no deploy, no impact on the bundle your real users download.
JavaScript content is now indexable. Bot traffic now receives fully-rendered HTML for every URL on your JavaScript site, while human visitors keep getting the exact same dynamic experience as before. Come back to PageGlass and run the scan again to confirm the fix.

The mental model for JavaScript SEO

Think of search engines and social crawlers as visitors who have disabled JavaScript in their browser. What would your site look like if you opened it with JavaScript off? For most modern JavaScript sites, the answer is "an empty page with a spinner". That's what Googlebot (on its first pass), Bingbot, Yandex, GPTBot, ClaudeBot, PerplexityBot, Facebook's preview bot, LinkedIn's preview bot, and Slack's unfurl bot all see. If you want your content indexed, previewed, or cited by AI, you need it to appear in the initial HTML response, not after JavaScript has built the page.

Common JavaScript SEO mistakes

Setting meta tags on DOMContentLoaded. This runs after the initial HTML response has been sent and the crawler has left. The meta tags you're setting will never be read by most bots.
Using client-side routing without a server fallback. If your server returns the same index.html for every route and lets JavaScript handle routing, crawlers get the same empty shell for every URL you ask them to index.
Relying on Google Search Console to confirm indexing. GSC uses the Web Rendering Service for URL inspection, which executes JavaScript. Your inspection results don't reflect what Bingbot, social bots, or AI crawlers see.
Setting canonical URLs via JavaScript. If the canonical tag is injected client-side, crawlers read the initial HTML, see no canonical, and treat every URL as unique content.
Assuming "Google can handle it". Google can, most of the time, eventually. Other crawlers cannot, and social share previews happen synchronously when someone pastes your URL into a chat or an email client. You only get one chance.

What actually works

Three paths: (1) rebuild with a framework that supports server-side rendering or static-site generation (Next.js App Router, Nuxt 3, SvelteKit, Astro, Remix), which gives you a permanent fix at the cost of a rewrite; (2) pre-render at build time with tools like react-snap or puppeteer-based scripts, which works if your routes are known and content is stable; or (3) use a prerendering service like PageGlass, which detects crawlers and serves them pre-rendered HTML without touching your code.