The rising prevalence of React in trendy net growth can’t be ignored.

React and different related libraries (like Vue.js) have gotten the de facto alternative for bigger companies that require advanced growth the place a extra simplistic strategy (like utilizing a WordPress theme) gained’t fulfill the necessities.

Regardless of that, SEOs didn’t initially embrace libraries like React on account of search engines like google struggling to successfully render JavaScript, with content material obtainable throughout the HTML supply being the desire.

Nonetheless, developments in each how Google and React can render JavaScript have simplified these complexities, leading to Website positioning not being the blocker for utilizing React.

Nonetheless, some complexities stay, which I’ll run by way of in this information.

On that notice, right here’s what we’ll cowl:

However first, what’s React?

React is an open-source JavaScript library developed by Meta (previously Fb) for constructing net and cell purposes. The principle options of React are that it is declarative, is component-based, and permits simpler manipulation of the DOM.

The only approach to perceive the elements is by considering of them as plugins, like for WordPress. They permit builders to rapidly construct a design and add performance to a web page utilizing element libraries like MUI or Tailwind UI.

If you’d like the complete lowdown on why builders love React, begin right here:

Rendering with React, a brief historical past

React implements an App Shell Mannequin, which means the overwhelming majority of content material, if not all, can be Shopper-side Rendered (CSR) by default.

CSR means the HTML primarily comprises the React JS library moderately than the server sending the complete web page’s contents throughout the preliminary HTTP response from the server (the HTML supply).

It’s going to additionally embody miscellaneous JavaScript containing JSON information or hyperlinks to JS information that include React elements. You may rapidly inform a web site is client-side rendered by checking the HTML supply. To try this, right-click and choose “View Web page Supply” (or CTRL + U/CMD + U).

Netflix's homepage source HTML

A screenshot of the homepage supply HTML.

If you happen to don’t see many strains of HTML there, the applying is probably going client-side rendering.

Nonetheless, while you examine the component by right-clicking and deciding on “Examine component” (or F12/CMD + ⌥ + I), you’ll see the DOM generated by the browser (the place the browser has rendered JavaScript).

The result’s you’ll then see the location has loads of HTML:

Lots of HTML

Notice the appMountPoint ID on the primary <div>. You’ll generally see a component like that on a single-page utility (SPA), so a library like React is aware of the place it ought to inject HTML. Know-how detection instruments, e.g., Wappalyzer, are additionally nice at detecting the library.

Editor’s Notice

Ahrefs’ Website Audit saves each the Uncooked HTML despatched from the server and the Rendered HTML within the browser, making it simpler to identify whether or not a web site has client-side rendered content material.

Gif showing Site Audit saves both Raw HTML and Rendered HTML

Even higher, you possibly can search each the Uncooked and Rendered HTML to know what content material is particularly being rendered client-side. Within the beneath instance, you possibly can see this web site is client-side rendering key web page content material, such because the <h1> tag.

Gif showing site is client-side rendering key page content

Joshua Hardwick

Web sites created utilizing React differ from the extra conventional strategy of leaving the heavy-lifting of rendering content material on the server utilizing languages like PHP—referred to as Server-side Rendering (SSR).

Flowchart showing the SSR process

The above exhibits the server rendering JavaScript into HTML with React (extra on that shortly). The idea is similar for websites constructed with PHP (like WordPress). It’s simply PHP being become HTML moderately than JavaScript.

Earlier than SSR, builders saved it even less complicated.

They’d create static HTML paperwork that didn’t change, host them on a server, after which ship them instantly. The server didn’t have to render something, and the browser typically had little or no to render.

SPAs (together with these utilizing React) at the moment are coming full circle again to this static strategy. They’re now pre-rendering JavaScript into HTML earlier than a browser requests the URL. This strategy is named Static Website Technology (SSG), often known as Static Rendering.

Two flowcharts showing the SSG process

In observe, SSR and SSG are related.

The important thing distinction is that rendering occurs with SSR when a browser requests a URL versus a framework pre-rendering content material at construct time with SSG (when builders deploy new code or an online admin adjustments the location’s content material).

SSR could be extra dynamic however slower on account of further latency whereas the server renders the content material earlier than sending it to the person’s browser.

SSG is quicker, because the content material has already been rendered, which means it may be served to the person instantly (which means a faster TTFB).

How Google processes pages

To grasp why React’s default client-side rendering strategy causes Website positioning points, you first have to know how Google crawls, processes, and indexes pages.

We will summarize the fundamentals of how this works in the beneath steps:

  1. Crawling – Googlebot sends GET requests to a server for the URLs within the crawl queue and saves the response contents. Googlebot does this for HTML, JS, CSS, picture information, and extra.
  2. Processing – This contains including URLs to the crawl queue discovered inside <a href> hyperlinks throughout the HTML. It additionally contains queuing useful resource URLs (CSS/JS) discovered inside <hyperlink> tags or photos inside <img src> tags. If Googlebot finds a noindex tag at this stage, the method stops, Googlebot gained’t render the content material, and Caffeine (Google’s indexer) gained’t index it.
  3. Rendering – Googlebot executes JavaScript code with a headless Chromium browser to seek out further content material throughout the DOM, however not the HTML supply. It does this for all HTML URLs.
  4. Indexing – Caffeine takes the knowledge from Googlebot, normalizes it (fixes damaged HTML), after which tries to make sense of all of it, precomputing some rating alerts prepared for serving inside a search end result.
Flowchart showing how Google crawls, processes, and indexes pages

Traditionally, points with React and different JS libraries have been on account of Google not dealing with the rendering step nicely.

Some examples embody:

  • Not rendering JavaScript – It’s an older challenge, however Google solely began rendering JavaScript in a restricted method in 2008. Nonetheless, it was nonetheless reliant on a crawling scheme for JavaScript websites created in 2009. (Google has since deprecated the scheme.)
  • The rendering engine (Chromium) being outdated – This resulted in a scarcity of assist for the most recent browser and JavaScript options. If you happen to used a JavaScript characteristic that Googlebot didn’t assist, your web page may not render appropriately, which might negatively affect your content material’s indexing.
  • Google had a rendering delay – In some instances, this might mean a delay of up to a few weeks, slowing down the time for adjustments to the content material to succeed in the indexing stage. This might have dominated out counting on Google to render content material for many websites.

Fortunately, Google has now resolved most of those points. Googlebot is now evergreen, which means it at all times helps the most recent options of Chromium.

As well as, the rendering delay is now 5 seconds, as introduced by Martin Splitt on the Chrome Developer Summit in November 2019:

Final yr Tom Greenaway and I have been on this stage and telling you, ‘Effectively, , it might take as much as per week, we’re very sorry for this.’ Overlook this, okay? As a result of the brand new numbers look quite a bit higher. So we truly went over the numbers and located that, it seems that at median, the time we spent between crawling and really having rendered these outcomes is – on median – it’s 5 seconds!”

This all sounds optimistic. However is client-side rendering and leaving Googlebot to render content material the best technique?

The reply is probably nonetheless no.

Widespread Website positioning points with React

Up to now 5 years, Google has innovated its dealing with of JavaScript content material, however fully client-side rendered websites introduce different points that it’s good to take into account.

It’s vital to notice that you possibly can overcome all points with React and Website positioning.

React JS is a growth device. React isn’t any totally different from some other device inside a growth stack, whether or not that’s a WordPress plugin or the CDN you select. The way you configure it’ll resolve whether or not it detracts or enhances Website positioning.

Finally, React is nice for Website positioning, because it improves person expertise. You simply have to be sure you take into account the next frequent points.

1. Choose the best rendering technique

Essentially the most important challenge you’ll have to sort out with React is how it renders content material.

As talked about, Google is nice at rendering JavaScript these days. However sadly, that isn’t the case with different search engines like google. Bing has some assist for JavaScript rendering, though its effectivity is unknown. Different search engines like google like Baidu, Yandex, and others supply restricted assist.


This limitation doesn’t solely affect search engines like google. Aside from web site auditors, Website positioning instruments that crawl the net and supply essential information on parts like a web site’s backlinks don’t render JavaScript. This will have a important affect on the standard of information they supply. The one exception is Ahrefs, which has been rendering JavaScript throughout the net since 2017 and presently renders over 200 million pages per day.

Introducing this unknown builds case for choosing a server-side rendered answer to make sure that all crawlers can see the location’s content material.

As well as, rendering content material on the server has one other essential profit: load instances.

Load instances

Rendering JavaScript is intensive on the CPU; this makes giant libraries like React slower to load and change into interactive for customers. You’ll usually see Core Internet Vitals, resembling Time to Interactive (TTI), being a lot larger for SPAs—particularly on cell, the first method customers eat net content material.

Overview of metrics' performance, including FCP, LCP, etc

An instance React utility that makes use of client-side rendering.

Nonetheless, after the preliminary render by the browser, subsequent load instances are typically faster as a result of following:

Relying on the variety of pages seen per go to, this may end up in discipline information being optimistic total.

Four bar graphs showing positive field data of FCP, LCP, FID, and CLS

Nonetheless, in case your web site has a low variety of pages seen per go to, you’ll wrestle to get optimistic discipline information for all Core Internet Vitals.


The best choice is to go for SSR or SSG primarily due to:

  • Quicker preliminary renders.
  • Not having to depend on search engine crawlers to render content material.
  • Enhancements in TTI on account of much less JavaScript code for the browser to parse and render earlier than changing into interactive.

Implementing SSR inside React is feasible by way of ReactDOMServer. Nonetheless, I like to recommend utilizing a React framework referred to as Subsequent.js and utilizing its SSG and SSR choices. You may as well implement CSR with Subsequent.js, however the framework nudges customers towards SSR/SSG on account of velocity.

Subsequent.js helps what it calls “Computerized Static Optimization.” In observe, this implies you possibly can have some pages on a web site that use SSR (resembling an account web page) and different pages utilizing SSG (resembling your weblog).

The end result: SSG and quick TTFB for non-dynamic pages, and SSR as a backup rendering technique for dynamic content material.


You’ll have heard about React Hydration with ReactDOM.hydrate(). That is the place content material is delivered by way of SSG/SSR after which turns right into a client-side rendered utility in the course of the preliminary render. This can be the plain alternative for dynamic purposes sooner or later moderately than SSR. Nonetheless, hydration presently works by loading the complete React library after which attaching occasion handlers to HTML that may change. React then retains HTML between the browser and server in sync. Presently, I can’t advocate this strategy as a result of it nonetheless has detrimental implications for net vitals like TTI for the preliminary render. Partial Hydration could resolve this sooner or later by solely hydrating essential components of the web page (like ones throughout the browser viewport) moderately than the complete web page; till then, SSR/SSG is the higher possibility.

Since we’re speaking about velocity, I’ll be doing you a disservice by not mentioning different methods Subsequent.js optimizes the essential rendering path for React purposes with options like:

  • Picture optimization – This provides width and peak <img> attributes and srcset, lazy loading, and picture resizing.
  • Font optimization – This inlines essential font CSS and provides controls for font-display.
  • Script optimization – This allows you to decide when a script must be loaded: earlier than/after the web page is interactive or lazily.
  • Dynamic imports – If you happen to implement greatest practices for code splitting, this characteristic makes it simpler to import JS code when required moderately than leaving it to load on the preliminary render and slowing it down.

Velocity and optimistic Core Internet Vitals are a rating issue, albeit a minor one. Subsequent.js options make it simpler to create nice net experiences that will provide you with a aggressive benefit.


Many builders deploy their Subsequent.js net purposes utilizing Vercel (the creators of Subsequent.js), which has a world edge community of servers; this leads to quick load instances.

Vercel gives information on the Core Internet Vitals of all websites deployed on the platform, however you can too get detailed net important information for every URL utilizing Ahrefs’ Website Audit.

Merely add an API key throughout the crawl settings of your tasks.

Text field to add API key

After you’ve run your audit, take a look on the efficiency space. There, Ahrefs’ Website Audit will present you charts displaying information from the Chrome Person Expertise Report (CrUX) and Lighthouse.

Pie charts and bar graphs showing data from CrUX and Lighthouse

2. Use standing codes appropriately

A standard challenge with most SPAs is that they don’t appropriately report standing codes. That is because the server isn’t loading the web page—the browser is. You’ll generally see points with:

  • No 3xx redirects, with JavaScript redirects getting used as an alternative.
  • 4xx standing codes not reporting for “not discovered” URLs.

You may see beneath I ran a check on a React web site with This web page ought to clearly be a 404 however, as an alternative, returns a 200 standing code. That is referred to as a tender 404.

Table showing URL on left. On right, under "Status codes," it shows "200"

The chance right here is that Google could resolve to index that web page (relying on its content material). Google might then serve this to customers, or it’ll be used when evaluating a web site.

As well as, reporting 404s helps SEOs audit a web site. If you happen to by chance internally hyperlink to a 404 web page and it’s returning a 200 standing code, rapidly recognizing the realm with an auditing device could change into way more difficult.

There are a few methods to unravel this challenge. If you happen to’re client-side rendering:

  1. Use the React Router framework.
  2. Create a 404 element that exhibits when a route isn’t acknowledged.
  3. Add a noindex tag to “not discovered” pages.
  4. Add a <h1> with a message like “404: Web page Not Discovered.” This isn’t superb, as we don’t report a 404 standing code. However it’ll stop Google from indexing the web page and assist it acknowledge the web page as a tender 404.
  5. Use JavaScript redirects when it’s good to change a URL. Once more, not superb, however Google does observe JavaScript redirects and go rating alerts.

If you happen to’re utilizing SSR, Subsequent.js makes this straightforward with response helpers, which allow you to set no matter standing code you need, together with 3xx redirects or a 4xx standing code. The strategy I outlined utilizing React Router can be put into observe whereas utilizing Subsequent.js. Nonetheless, if you’re utilizing Subsequent.js, you’re probably additionally implementing SSR/SSG.

3. Keep away from hashed URLs

This challenge isn’t as frequent for React, however it’s important to keep away from hash URLs like the next:


Typically, Google isn’t going to see something after the hash. All of those pages can be seen as


SPAs with client-side routing ought to implement the Historical past API to alter pages.

You are able to do this comparatively simply with each React Router and Subsequent.js.

4. Use <a href> hyperlinks the place related

A standard mistake with SPAs is utilizing a <div> or a <button> to alter the URL. This isn’t a difficulty with React itself, however how the library is used.

Doing this presents a difficulty with search engines like google. As talked about earlier, when Google processes a URL, it appears for added URLs to crawl inside <a href> parts.

If the <a href> component is lacking, Google gained’t crawl the URLs and go PageRank.


The answer is to incorporate <a href> hyperlinks to URLs that you really want Google to find.

Checking whether or not you’re linking to a URL appropriately is simple. Examine the component that internally hyperlinks and test the HTML to make sure you’ve included <a href> hyperlinks.

As within the above instance, you might have a difficulty in the event that they aren’t.

Nonetheless, it’s important to know that lacking <a href> hyperlinks aren’t at all times a difficulty. One good thing about CSR is that when content material is useful to customers however not search engines like google, you possibly can change the content material client-side and never embody the <a href> hyperlink.

Within the above instance, the location makes use of faceted navigation that hyperlinks to doubtlessly tens of millions of combos of filters that aren’t helpful for a search engine to crawl or index.

List of genres

Loading these filters client-side is sensible right here, as the location will preserve crawl price range by not including <a href> hyperlinks for Google to crawl.

Subsequent.js makes this simple with its hyperlink element, which you’ll configure to permit client-side navigation.

If you happen to’ve determined to implement a totally CSR utility, you possibly can change URLs with React Router utilizing onClick and the Historical past API.

5. Keep away from lazy loading important HTML

It’s frequent for websites developed with React to inject content material into the DOM when a person clicks or hovers over a component—just because the library makes that simple to do.

This isn’t inherently dangerous, however content material added to the DOM this manner is not going to be seen by search engines like google. If the content material injected contains vital textual content material or inside hyperlinks, this will likely negatively affect:

  • How nicely the web page performs (as Google gained’t see the content material).
  • The discoverability of different URLs (as Google gained’t discover the interior hyperlinks).

Right here’s an instance on a React JS web site I lately audited. Right here, I’ll present a widely known e‑commerce model with vital inside hyperlinks inside its faceted navigation.

Nonetheless, a modal exhibiting the navigation on cell was injected into the DOM while you clicked a “Filter” button. Watch the second <!—-> throughout the HTML beneath to see this in observe:

Gif of modal showing the navigation on mobile was injected into DOM


Recognizing these points isn’t simple. And so far as I do know, no device will instantly let you know about them.

As a substitute, it is best to test for frequent parts such as:

  • Accordions
  • Modals
  • Tabs
  • Mega menus
  • Hamburger menus

You’ll then want to examine the component on them and watch what occurs with the HTML as you open/shut them by clicking or hovering (as I’ve carried out within the above GIF).

Suppose you discover JavaScript is including HTML to the web page. In that case, you’ll have to work with the builders. That is so that moderately than injecting the content material into the DOM, it’s included throughout the HTML by default and is hidden and proven by way of CSS utilizing properties like visibility: hidden; or show: none;.

6. Don’t overlook the basics

Whereas there are further Website positioning issues with React purposes, that doesn’t imply different fundamentals don’t apply.

You’ll nonetheless want to ensure your React purposes observe greatest practices for:

Ultimate ideas

Sadly, working with React purposes does add to the already lengthy record of points a technical Website positioning must test. However due to frameworks like Subsequent.js, it makes the work of an Website positioning way more simple than what it was traditionally.

Hopefully, this information has helped you higher perceive the extra issues it’s good to make as an Website positioning when working with React purposes.

Have any questions on working with React? Tweet me.

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