JavaScript

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JavaScript

Basic Information
Release Year	1995
Product Type	Software
In Production	Yes
Official Website	https://tc39.es/ecma262/multipage/

JavaScript (JS) is a programming language and core technology of the Web, alongside HTML and CSS. It was created by Brendan Eich in 1995. As of 2025, the overwhelming majority of websites (98.9%) uses JS for client-side webpage behavior. It's even used on the server-side (see Node.js).

Consumer-impact summary

• Degraded accessibility: Dynamic and/or active content is well-known to have poor accessibility for users with visual and/or cognitive impairments. While standards such as WAI-ARIA were created to mitigate this, it's no silver bullet, especially when developers aren't aware of ARIA.
• Lack of transparency: To optimize network bandwidth, JS code is typically served in minified form, which makes it harder to understand for humans. This is particularly problematic if the original source is not publicly available, which is typically the case of proprietary software.
• Excessive tracking: JS is much more capable than HTML and CSS combined to track user behavior, because of its first-class access to user-agent (UA) APIs. JS can communicate with almost any server (only limited by CORS) at any time (limited by connection availability), using a plethora of protocols. JS can get hardware information and compute a fingerprint of the device, user, or both.
• Market control: JS (alongside Wasm) are built into almost every web-browser and UA, including "light-weight" ones (such as w3m). Incentivizing companies to use it for everything, since "there's no need to worry about compatibility or portability". Some people say that JS shouldn't even be a Web Standard, implying that it should be an extension or plug-in (such as Java Applets and Adobe Flash) the user willingly installs; this would reduce the incentive to use JS, as there's no guarantee the user has it.
• Security risks: JS is well-known for being a poorly-designed tool. This leads to programmers and even experienced software-devs to accidentally add vulnerabilities to their code. That, and the fact that JS is Turing-complete (both in practice and in theory) is a recipe for disaster, as it makes debugging and reverse-engineering impractical in big code-bases. It's worth noting that tooling, such as TypeScript and ESLint, exist to substantially minimize the likelihood of bugs.

How it works

Whenever a user visits a webpage, an average web-browser will execute the JS code it finds in <script> tags. This code could do anything from updating part of the page only when the user requests it, to showing a popup/popunder.

When JS tries to access a "privacy-sensitive" Web API (such as the microphone) the browser pauses it until the user has granted access to that API. This is typically done on a per-domain basis. However, as mentioned earlier, many other APIs don't need to ask permission before fetching data.

Why it is a problem

Note that, despite its flaws, JS typically is not a problem on its own, but it becomes a problem when given too much power.

Many webpages (and even entire websites), force the user to keep JS enabled, otherwise they break or deliberately refuse to work. In 2026, considering the advancements in HTML and CSS technology, there is minimal reason why an average website (excluding real-time simulations and low-latency gaming) would ever need JS. The only valid justification are legacy code-bases, as those are impractical to migrate to no-JS solutions.

Expanding on the tracking capability, JS makes it harder for ad-blockers to block ads, since it can be used to make overly-dynamic ads. The data collected by malicious JS makes it trivial to serve personalized ads, even across unrelated sites.

Expanding on the security risks, these are the most common vulnerabilities found in JS code:

• XSS, which NoScript tries to mitigate
• Arbitrary code execution and code injection. Typically caused by eval (part of the ECMAScript spec), but there are Web APIs (such as setTimeout and setInterval) that can be misused as well.
• Remote code execution. This is used by hackers and crackers to build bot-nets for DDoS or crypto-mining, but it's mostly used for spyware since it can hide more easily.

Browser-engine developers (such as Google and Mozilla) not only feel compelled, but are economically incentivized to optimize JS to its limits. This leads to complex code-bases that are harder to verify for correctness. Browser vendors mitigate this via sandboxing. Unfortunately, since modern browsers compile JS to native CPU code (see JIT) to improve performance, this introduces a higher risk of sandbox-escape.

JS not only makes pages "dynamic", the language itself is very dynamic, which is hard to optimize by engines. To put into perspective how much JS can slow down rendering, someone bench-marked a bloated pure-HTML page and a "simple" React app, the bloated HTML had faster FMP.

Incidents

This is a list of all consumer-protection incidents related to this technology. Any incidents not mentioned here can be found in the JavaScript category.

Google Search requires JS (2025)

In January 2025, Google's web-search engine mandates that user-agents must have JS enabled. Google's justification was that it's a defense mechanism against abusive bots (see also Deceptive language frequently used against consumers). However, some people claim that it's an invalid justification.

List of sites refusing to work without JS

The following is a non-exhaustive list of websites where most or all pages deliberately only work with JS enabled:

• YouTube
• Facebook. It used to work without it, but at some point it became mandatory. Some people claim that it's possible to use without JS when visiting the "lite" or "mobile basic" variants.^{[citation needed]}
• Instagram
• Twitter. It also used to work without it, but some time after being bought by Elon Musk, it became mandatory.^{[citation needed]}
• Bluesky:
  • The web app (bsky.app) shows this message if JS is disabled

    This is a heavily interactive web application, and JavaScript is required. Simple HTML interfaces are possible, but that is not what this is.

    which is questionable at best
  • Its legal docs (ToS, PP, CG) need JS to be viewed by humans, however this seems more of an oversight than deliberate

Benefits

It's worth noting that, while JS is trivial to misuse and abuse, JS can enhance the user-experience (UX). The World Wide Web Consortium (W3C) provides comprehensive guidelines for such purposes.

External links

• LibRedirect explaining why it exists, and how Google Chrome's MV3 limits it
• Google being anti-competitive towards Firefox: https://github.com/uBlockOrigin/uBlock-issues/discussions/3240
• Instagram refusing to serve content to noscript users, and deliberately nagging them to install the app or login: https://github.com/Rudxain/uBO-rules/pull/9
• Websites that nag users to enable JS, even when it provides negligible value
• Discord being extremely bloated to the point of crashing when opening Developer-tools: https://github.com/Rudxain/uBO-rules/blob/42220bd4f80052ee15136dff7269df19529c43ec/rx.ubo#L3-L19. This is not the fault of bloated JS, it's likely a bloated DOM-tree, but discord only bloats the DOM when JS is enabled.
• "Enough with the JavaScript already!"
• "Maybe we could tone down the JavaScript"
• "You don't need JavaScript for that"
• "You really don't need all that JavaScript, I promise"
• "Progressive Enhancement Still Important"
• "Everyone has JS, right?"
• "Shipping a button in 2026…", by Kai Lentit. This illustrates the burnout and fatigue software developers can experience on a daily basis
• HTMX developer advocating for less JS
• "Web Obesity Crisis"
• "How web bloat impacts users with slow connections"
• JS bloat (2024)
• How JS makes web apps more unstable
• GNU/FSF explaining why JS takes freedom away
• GNU/FSF explaining why "web apps" shouldn't exist. WARNING: contains overzealous claims! (according to Rudxain). Related: Local-first
• "I Used The Web For A Day With JavaScript Turned Off"
• More sources (TO-DO)

See also

• Electron