JavaScript & SEO: what non-technical marketers should understand

Picture a webpage that looks perfect to you. Headline in place, product tiles lined up, filters working, and a glossy hero image. Now picture a search bot arriving and finding… a near-empty shell, plus a polite note that says “Loading”.

That’s the JavaScript and SEO problem in one scene. JavaScript can change what Google can read, and when it can read it. Most of the time, it’s fine. Sometimes it quietly blocks pages from being understood, crawled, or indexed on time, especially after a redesign.

This guide keeps it plain and practical: what can go wrong, what “good” looks like, what to ask developers, and a few checks you can run without writing a line of code.

JavaScript and SEO in plain English: what changes when pages are built in the browser

JavaScript is the part of a site that makes things interactive. It powers sliders, filters, pop-ups, and sometimes the entire page layout. It can also load content after the page arrives, pulling text and products in later.

Here’s the key idea for SEO: search engines do best when the important stuff is present in the first HTML response. If the content only appears after scripts run, the bot has extra work to do, and that can lead to delays or gaps.

JavaScript isn’t “bad” for SEO. It’s just a different way of building pages, and it needs a set-up that doesn’t hide the goods.

How Google sees a JavaScript page (fetch first, render later)

Google often works in two steps:

1. Fetch: it requests the page and reads the raw HTML it gets back.
2. Render: it may then run JavaScript (like a browser) to see the full page.

That second step can take time, and it doesn’t always happen the way you’d expect. Heavy scripts, blocked resources, or messy routing can mean Google doesn’t see the same page a user sees.

Google has improved a lot at rendering modern JavaScript, but fast, clear HTML still wins. You get quicker discovery, steadier crawling, and fewer surprises when a template changes.

If you want a wider set of examples and patterns (especially for common frameworks), this beginner-friendly guide from Conductor is a useful reference: https://www.conductor.com/academy/javascript-seo/

What “rendering” means for visibility, indexing speed, and reporting

Rendering is Google “building” the page. It’s like it’s opening your page in a simplified Chrome, waiting for scripts to run, then taking a snapshot of what appears.

Marketers feel rendering problems as real-world pain:

• Slow indexing: new pages take days to appear, even after an XML sitemap submit.
• Drops after a redesign: traffic falls, and nobody touched the keywords.
• Reporting mismatch: analytics shows visits, but Search Console shows weak coverage or “Crawled, currently not indexed”.

There’s another catch. Not every bot runs JavaScript fully. Social previews, some SEO tools, and some smaller search engines can grab the raw HTML and stop there. If your open graph tags, headings, or main copy only exist after rendering, sharing and discovery can suffer.

A simple rule helps: treat the first HTML like the shop window. If the window is empty, fewer people walk in.

The JavaScript SEO problems marketers can spot before rankings drop

You don’t need to read code to catch early warning signs. Watch outcomes: what’s visible quickly, what’s clickable, and what feels slow or fragile.

This matters most on pages that should pull search traffic every day, like product pages, category pages, location pages, and news articles. Those pages need to be easy to find, easy to crawl, and clear about what they’re about.

Content that loads late or not at all (blank pages, missing headings, thin HTML)

A common pattern is “frame first, content later”. The server sends a basic layout, then JavaScript fetches the real copy and links.

If rendering fails, stalls, or is delayed, Google may index a page that looks thin, or it may not index it at all.

What should be present early (in the first HTML) on any page you care about ranking?

The page title, the main heading (H1), a chunk of core copy, key internal links, and your primary images (with sensible alt text). These are the parts that help search engines understand topic, relevance, and site structure.

A quick gut-check: if you load a page on poor mobile data, does the main message appear fast, or do you stare at a blank skeleton?

If you want a marketer-focused overview of the typical failure points, Found’s write-up is UK-friendly and practical: https://www.found.co.uk/blog/javascript-seo-best-practices/

Navigation and internal links that only work with JavaScript

Search engines crawl the web by following links. If your internal links only appear after a script runs, or they rely on click events instead of real anchor tags, crawling can thin out.

This often shows up on:

• Category pages where product grids and pagination are injected late.
• Sites using single-page app routing, where URLs don’t behave like normal pages.
• Mega menus that look fine to users, but aren’t present in the initial HTML.

Practical checks you can do as a marketer:

Link reality check: can you right-click a category link and copy it? Does it look clean (not a long string of symbols)?
Back button check: does the back button behave normally, or does it trap you?
No-script sanity check: if scripts fail, can you still reach key pages from the navigation?

Hash-only routing (URLs with # doing all the work) can be risky for important SEO pages. Modern frameworks can handle routing well, but the set-up must produce crawlable URLs and stable page states.

Speed issues from heavy scripts that quietly hurt SEO

JavaScript affects SEO through speed as much as content. Bigger scripts mean more downloading, more processing, and more waiting before a page becomes usable.

This isn’t abstract. It shows up as delayed clicks, janky scrolling, and users abandoning category pages before they even see products. Search engines can pick up on that through performance signals and reduced engagement.

Marketers often influence the biggest causes:

Too many tags: ad pixels, extra analytics, heatmaps, and affiliate scripts.
Chat widgets: useful, but sometimes heavy.
A/B testing tools: fine when controlled, messy when stacked.
Ad tech: the fastest way to turn a quick page into a slow one.

A good habit is to treat scripts like items in hand luggage. If it doesn’t earn its place, it doesn’t fly.

For a broad set of JavaScript SEO checks (and how teams typically fix them), Backlinko’s guide is a solid overview: https://backlinko.com/javascript-seo

What to ask your developers (and what “good” looks like)

Your goal isn’t to ban JavaScript. It’s to ask for a page that’s useful on first response, then improved with JavaScript.

If you want a short briefing you can paste into a ticket, use this framing:

• Search engines and users should get real content and links quickly.
• JavaScript can enhance the experience, but it shouldn’t be required to understand the page.
• Signals like canonicals and structured data should not depend on late-running scripts.

Choose the right rendering approach: SSR, pre-rendering, or static pages

Rendering choices sound technical, but the trade-offs are easy to explain.

Here’s a simple view of common options:

Frameworks like Next.js can support SSR and SSG, and many teams use hybrid set-ups. The marketing take is simple: money pages should not wait for the browser to assemble the basics.

Google’s documentation in recent years has also pushed teams away from old “dynamic rendering” workarounds, and towards cleaner SSR, SSG, or hybrid builds. The more standard the approach, the fewer edge cases you inherit.

Progressive enhancement: start with HTML, then add JavaScript

Progressive enhancement means the page works even if scripts fail. Think of it like a newspaper: the story must still be readable if the glossy inserts fall out.

What should work without JavaScript on an SEO page?

• Reading the main story or product description
• Seeing headings in order (H1, then H2s)
• Clicking core navigation
• Reaching key pages through links that exist in the HTML

Ask developers for semantic HTML. That means real headings and real links, not clickable divs styled to look like buttons. This helps accessibility, and it also helps search engines understand the page’s structure.

If you want a longer, plain-English walkthrough of common JavaScript SEO pitfalls (and why “Google can handle it” isn’t the whole story), The Method’s guide is a useful read: https://blog.hellomethod.co.uk/javascript-seo-best-practices

Technical basics that protect SEO: metadata, canonicals, structured data, and clean URLs

When JavaScript is involved, some teams inject SEO signals late. That’s where odd problems start.

Ask for these to be present in the initial HTML where possible:

• Title tag and meta description
• Canonical tag (the preferred URL for that page)
• Robots meta (index or noindex)
• Hreflang (if you run multi-country or multi-language pages)
• Structured data (schema markup for rich results)

Canonicals deserve special attention. Google has clarified that it may look at canonicals in the raw HTML and again after rendering. If your canonical changes after scripts run, you can end up sending mixed signals. The clean answer is: make the canonical consistent, and ideally present from the first response.

Also push for tidy URL rules. “One page, one main URL” prevents duplicate pages caused by filters, tracking parameters, and client-side routing quirks. If you need faceted navigation, ask for a clear plan on which filter states are indexable.

Neil Patel’s guide includes examples of how these technical pieces affect crawling and indexing, which can help when you need to explain the risk to non-SEO stakeholders: https://neilpatel.com/blog/javascript-seo/

Easy checks non-technical marketers can run (no coding required)

These are quick habits after launches, template updates, or tag changes. They don’t replace a technical audit, but they catch the issues that hurt rankings.

Use Google Search Console URL Inspection to compare HTML vs rendered page

Open Search Console, inspect a URL, then look at:

• Whether it’s indexed
• The rendered page view
• The rendered HTML

What “good” looks like: the rendered page matches what users see, and the rendered HTML contains the main heading, meaningful text, and internal links.

Red flags to screenshot and send to developers:

• Main copy missing or replaced by placeholders
• Important internal links missing
• Canonical pointing to the wrong page
• Resources blocked (which can stop full rendering)

Test three types of pages: a top landing page, a deep article, and a category page. JavaScript issues often hide in templates, so sampling page types is more useful than sampling keywords.

Run Lighthouse or PageSpeed Insights to spot JavaScript bloat and slow interaction

Lighthouse and PageSpeed Insights translate performance into plain signals: how fast the page appears, how soon it responds, and what’s slowing it down.

Focus on trends, not one-off scores. If performance drops after adding a new tag or widget, you’ve probably found the cause.

A few marketer-friendly actions to request:

Script audit: list every third-party tag, who owns it, and what it’s for.
Defer non-essential scripts: load the nice-to-haves later.
Lazy-load below-the-fold features: don’t make the top of the page wait for the bottom.

Speed isn’t only an SEO concern. It’s revenue, too. A fast category page gets people to products. A slow one sends them back to the search results.

Conclusion

JavaScript doesn’t break SEO by default, but hiding key content behind it can. Keep three ideas close: make the main content visible in the first HTML, keep pages fast by limiting scripts, and test important URLs in Search Console after changes.

Pick one high-value page today and run URL Inspection. If the rendered view doesn’t match reality, share that evidence with your developers and ask for a fix. Your best rankings usually come from the simplest promise: what users see is what Google gets.