What React is, and why we build with it

Most quotes for a website name a technology and stop there. “Built in React” sounds reassuring, but it does not tell you what you are paying for or what it will cost your visitors. This post explains React in plain words, gives the evidence for its benefits, is honest about its main cost, and shows how we use it on this site. Every factual claim carries a numbered citation; the reference list is at the end.

What React is

React is a JavaScript library for building user interfaces. Its maintainers describe it simply as “the library for web and native user interfaces”, and it is released under the MIT licence, which means anyone can use it without paying a licence fee^[5]. It was created at Facebook and released publicly in 2013. Pete Hunt, one of its early engineers, explained the motivation at the time: “React is a library for building composable user interfaces. It encourages the creation of reusable UI components which present data that changes over time.”^[1]

That sentence still describes the core idea. A React application is made of components. The official documentation puts it plainly: “Components are one of the core concepts of React. They are the foundation upon which you build user interfaces”^[2]. A component is a small piece of the page, such as a menu, a form step or a price table, written once and reused wherever it is needed.

How React thinks

Three ideas explain most of what makes React different from the way websites were built before it.

A page is a tree of components. React’s own tutorial, “Thinking in React”, starts by drawing boxes around every part of a design and naming them. It notes that “UI and data models often have the same information architecture, that is, the same shape”^[3]. In practice this means the structure of your site’s content and the structure of its code line up, which keeps changes small and predictable.

Data flows one way. Information moves from parent components down to children, and children ask the parent to change it. The documentation calls this “one-way data flow because the data flows down from the top-level component to the ones at the bottom of the tree”^[3]. One-way flow is why a React interface rarely gets into a state nobody can explain.

React updates only what changed. When something on the page changes, React works out the new result and then applies the smallest set of changes to the browser. In the documentation’s words, “React only changes the DOM nodes if there’s a difference between renders”^[4]. This is what makes an interactive React interface feel immediate: typing in one field does not redraw the whole page.

The benefits, with evidence

Reuse, consistency and fewer bugs

Because every part of the interface is a component, the same price table, form step or button is one piece of code used many times. Fix it once and it is fixed everywhere. This is the “reusable UI components” idea from the original 2013 announcement^[1], and it is the reason a React site stays consistent as it grows.

A very large pool of developers

The people who will maintain your site in five years matter more than the technology chosen today. React has the largest developer base of any web user-interface library. In Stack Overflow’s 2025 Developer Survey, 44.7% of all respondents reported using React, second only to the Node.js runtime and well ahead of Angular (18.2%) and Vue.js (17.6%)^[6]. The HTTP Archive’s 2024 Web Almanac, which measures real websites rather than survey answers, found React on 10% of pages, up from 8% the year before^[7]. Whoever you hire after us will know it.

Long-term stewardship

React is no longer controlled by a single company. In February 2026 the project moved to the React Foundation, hosted by the Linux Foundation^[11], following the announcement of the foundation in October 2025^[12]. For a business, that lowers the risk that the library your site depends on is abandoned or taken in a direction that suits one vendor.

Tooling that catches mistakes before your customers do

React works with TypeScript, a typed version of JavaScript that catches a whole class of errors while code is being written. The documentation notes that “out of the box, TypeScript supports JSX and you can get full React Web support” by adding two type packages^[13]. Every React component on this site is written in TypeScript.

The library keeps getting better without rewrites

React 19, released on 5 December 2024, added Actions for form handling, where “Actions automatically manage submitting data for you”, along with Server Components, which render parts of a page ahead of time in “a separate environment”^[8]. React 19.2 followed on 1 October 2025^[9]. On 7 October 2025 the React Compiler reached version 1.0^[10]; it “automatically optimizes your React application by handling memoization for you”, removing a category of manual performance work^[14]. Sites written in React today inherit these improvements as upgrades, not rebuilds.

One way of thinking, on the web and in apps

If your business later needs a mobile app, React Native applies the same component model to native Android and iOS apps under the slogan “Learn once, write anywhere”^[15]. Its own site lists Microsoft Office, Shopify, Discord and Amazon Shopping among the apps built with it^[15]. The skills and much of the code carry over.

The honest cost: JavaScript weighs something

React runs in your visitor’s browser, and that has a price. The 2024 Web Almanac reports that the median web page now ships 558 kilobytes of JavaScript on mobile and 613 kilobytes on desktop, a 14% rise in a year^[7]. Every kilobyte has to be downloaded and executed before the page is fully usable.

That matters because speed changes behaviour. Google’s summary of the evidence reports that “the BBC found they lost an additional 10% of users for every additional second their site took to load”, and that Rakuten 24’s work on Core Web Vitals “increased revenue per visitor by 53.37% and conversion rate by 33.13%”^[16]. Google’s own thresholds for a good page are a Largest Contentful Paint of 2.5 seconds or less, an Interaction to Next Paint of 200 milliseconds or less, and a Cumulative Layout Shift of 0.1 or less^[17]. A marketing site that ships a full React application to render a paragraph of text is paying that cost for no return.

How we use React without paying for it everywhere

The answer is an approach called islands. Katie Sylor-Miller of Etsy coined the term “component island” in 2019, and Jason Miller, creator of Preact, described the pattern in 2020: “render HTML pages on the server, and inject placeholders or slots around highly dynamic regions”^[18]. Everything else on the page is plain HTML.

We build on Astro, which was designed around this idea. Astro’s documentation explains that “the majority of your website is converted to fast, static HTML and JavaScript is only loaded for the individual components that need it”^[19]. Its stated principles are content first and server first: “Websites run faster when they render HTML on the server”^[20]. React is one of the frameworks Astro supports for those interactive pieces^[20].

On this site, React runs exactly four things: the job board on the home page, the brief builder, the mobile menu and the Perth clock in the header. Everything else, including this article, is static HTML. The result is a home page that weighs 169 kilobytes in total, fonts included, and scores 100 on all four Lighthouse categories; the figures are published on the home page with the date they were measured. The finished site is deployed to Cloudflare Pages, which lets us “create full-stack applications that are instantly deployed to the Cloudflare global network”^[21], so those small files are served from a location near your visitor.

When React is the wrong answer

Sometimes the right amount of React is none. A single landing page with a phone number and a contact form does not need a component library, and we will quote it as plain HTML and CSS, which is the most durable and the cheapest to host. React earns its place when a page has real interactivity: multi-step forms, filters, calculators, anything that must update as the visitor acts. Our job is to tell you which of those you are buying, and to put the JavaScript only where it pays for itself.

If you are weighing up a build, the brief builder takes three minutes and we will come back with a recommended stack and a fixed price.

Reference list

All sources accessed 7 May 2026.

1. Hunt, P. (2013) Why did we build React? React Blog, 5 June 2013. Meta. https://legacy.reactjs.org/blog/2013/06/05/why-react.html
2. Meta Open Source (n.d.) Your First Component. React documentation. https://react.dev/learn/your-first-component
3. Meta Open Source (n.d.) Thinking in React. React documentation. https://react.dev/learn/thinking-in-react
4. Meta Open Source (n.d.) Render and Commit. React documentation. https://react.dev/learn/render-and-commit
5. facebook/react (2026) React: The library for web and native user interfaces. GitHub repository, MIT licence. https://github.com/facebook/react
6. Stack Overflow (2025) 2025 Developer Survey: Technology, Web frameworks and technologies. https://survey.stackoverflow.co/2025/technology
7. Amjad, A. H. and Goel, N. (2024) 'JavaScript', in The 2024 Web Almanac. HTTP Archive. https://almanac.httparchive.org/en/2024/javascript
8. The React Team (2024) React v19. React Blog, 5 December 2024. https://react.dev/blog/2024/12/05/react-19
9. The React Team (2025) React 19.2. React Blog, 1 October 2025. https://react.dev/blog/2025/10/01/react-19-2
10. The React Team (2025) React Compiler v1.0. React Blog, 7 October 2025. https://react.dev/blog/2025/10/07/react-compiler-1
11. The React Team (2026) The React Foundation: A New Home for React Hosted by the Linux Foundation. React Blog, 24 February 2026. https://react.dev/blog/2026/02/24/the-react-foundation
12. The React Team (2025) Introducing the React Foundation. React Blog, 7 October 2025. https://react.dev/blog/2025/10/07/introducing-the-react-foundation
13. Meta Open Source (n.d.) Using TypeScript. React documentation. https://react.dev/learn/typescript
14. Meta Open Source (n.d.) React Compiler. React documentation. https://react.dev/learn/react-compiler
15. Meta Platforms (n.d.) React Native: Learn once, write anywhere. https://reactnative.dev/
16. Google (n.d.) Why does speed matter? web.dev. https://web.dev/articles/why-speed-matters
17. Google (n.d.) Web Vitals. web.dev. https://web.dev/articles/vitals
18. Miller, J. (2020) Islands Architecture. 11 August 2020. https://jasonformat.com/islands-architecture/
19. Astro (n.d.) Islands architecture. Astro documentation. https://docs.astro.build/en/concepts/islands/
20. Astro (n.d.) Why Astro? Astro documentation. https://docs.astro.build/en/concepts/why-astro/
21. Cloudflare (n.d.) Cloudflare Pages. Cloudflare Docs. https://developers.cloudflare.com/pages/