Web

/riˈækt/

n. “A library that thinks fast and renders faster.”

React is a JavaScript library for building user interfaces, primarily for web applications. Created by Facebook, it allows developers to design complex, interactive UIs by breaking them down into reusable components. Each component manages its own state and renders efficiently when that state changes, providing a reactive user experience.

At the core of React is the concept of a virtual DOM. Rather than directly manipulating the browser’s DOM, React maintains a lightweight copy of the DOM in memory. When a component’s state changes, React calculates the minimal set of changes needed to update the real DOM, reducing unnecessary reflows and improving performance.

Example: Suppose you have a comment section. Each comment is a React component. If a user edits one comment, only that component re-renders, not the entire list. This makes updates fast and predictable.

React uses a declarative syntax with JSX, which looks like HTML but allows embedding JavaScript expressions. Developers describe what the UI should look like for a given state, and React ensures the actual DOM matches that description. This approach contrasts with imperative DOM manipulation, making code easier to reason about and debug.

Beyond the core library, React has an ecosystem including React Router for navigation, Redux for state management, and Next.js for server-side rendering. These tools enable large-scale, maintainable applications while keeping components modular and testable.

Security and performance considerations are critical in React. Since React directly interacts with the DOM, improper handling of untrusted input can lead to XSS vulnerabilities. Additionally, developers must manage state and props efficiently to avoid unnecessary renders and memory leaks.

In essence, React is not just a library; it is a methodology for building modern, component-driven web applications that are fast, predictable, and maintainable. Its declarative, reactive nature has influenced countless frameworks and continues to shape how developers approach UI development.

/ˈdiː-ˈoʊ-ˈɛm/

n. “Where the browser meets your code.”

DOM, short for Document Object Model, is a programming interface for HTML and XML documents. It represents the page so scripts can change the document structure, style, and content dynamically. Think of it as a live map of the web page: every element, attribute, and text node is a node in this tree-like structure that can be accessed and manipulated.

When a browser loads a page, it parses the HTML into the DOM. JavaScript can then traverse this structure to read or modify elements. For instance, you can change the text of a paragraph, add a new image, or remove a button — all without reloading the page. This dynamic interaction is the foundation of modern web applications and frameworks.

The DOM treats documents as a hierarchy: the document is the root node, containing elements, attributes, and text nodes. Each element is a branch, each text or attribute a leaf. Scripts use APIs such as getElementById, querySelector, or createElement to navigate, modify, or create new nodes. Events, like clicks or key presses, bubble through this tree, allowing developers to respond to user interaction.

Example: Clicking a button might trigger JavaScript that locates a div via the DOM and updates its content. Frameworks like React or Angular build virtual DOMs to efficiently update the visible DOM without unnecessary reflows or repaints, improving performance.

Beyond HTML, the DOM is standardized by the W3C, ensuring consistency across browsers. This makes cross-browser scripting feasible, even if implementations vary slightly. Security considerations are tied closely to the DOM: XSS attacks exploit the ability to inject malicious scripts into the document tree, showing how central the DOM is to web security.

In essence, the DOM is the living interface between static markup and dynamic behavior. It enables scripts to read, modify, and react to the document, forming the backbone of interactive, responsive, and modern web experiences.

/ˌɛks-ɛs-ˈɛs/

n. “Sneaky scripts slipping where they shouldn’t.”

XSS, short for Cross-Site Scripting, is a class of web security vulnerability that allows attackers to inject malicious scripts into web pages viewed by other users. Unlike server-side attacks, XSS exploits the trust a user has in a website, executing code in their browser without their consent or knowledge.

There are three main types of XSS: Reflected, Stored, and DOM-based. Reflected XSS occurs when malicious input is immediately echoed by a web page, such as through a search query or URL parameter. Stored XSS involves the attacker saving the payload in a database or message forum so it executes for anyone viewing that content. DOM-based XSS happens when client-side JavaScript processes untrusted data without proper validation.

A classic example: a user clicks on a seemingly normal link that contains JavaScript in the query string. If the website fails to sanitize or escape the input, the script runs in the victim’s browser, potentially stealing cookies, session tokens, or manipulating the page content. XSS attacks can escalate into full account takeover, phishing, or delivering malware.

Preventing XSS relies on a combination of techniques: input validation, output encoding, and content security policies. Frameworks often include built-in escaping functions to ensure that user input does not become executable code. For example, in HTML, characters like < and > are encoded to prevent interpretation as tags. In modern web development, using libraries that automatically sanitize data, alongside Content Security Policy, greatly reduces risk.

XSS remains one of the most common vulnerabilities in web applications, making awareness critical. Even large, popular sites can fall victim if validation and sanitization practices are inconsistent. Testing tools, such as automated scanners, penetration tests, and bug bounty programs, often prioritize XSS detection due to its prevalence and impact.

In essence, XSS is about trust and control. Users trust a website to deliver content safely; attackers exploit that trust to execute unauthorized scripts. Proper sanitization, rigorous coding practices, and security policies are the antidotes, turning a website from a potential playground for malicious scripts into a secure, trustworthy environment.

/ˈdʌbəljuː-ˈeɪ-ɛf/

n. “A gatekeeper that filters the bad, lets the good pass, and occasionally throws tantrums.”

WAF, short for Web Application Firewall, is a specialized security system designed to monitor, filter, and block HTTP traffic to and from a web application. Unlike traditional network firewalls that focus on ports and protocols, a WAF operates at the application layer, understanding web-specific threats like SQL injection, cross-site scripting (XSS), and other attacks targeting the logic of web applications.

A WAF sits between the client and the server, inspecting requests and responses. It applies a set of rules or signatures to detect malicious activity and can respond in several ways: block the request, challenge the client with a CAPTCHA, log the attempt, or even modify the request to neutralize threats. Modern WAF solutions often include learning algorithms to adapt to the traffic patterns of the specific application they protect.

Consider an example: a user submits a form on a website. Without a WAF, an attacker could inject SQL commands into input fields, potentially exposing databases. With a WAF, the request is inspected, recognized as suspicious, and blocked before it reaches the backend, preventing exploitation.

WAFs can be deployed as hardware appliances, software running on a server, or cloud-based services. Popular cloud-based offerings integrate seamlessly with CDNs and CDN services, combining traffic acceleration with security filtering. Rulesets may follow well-known standards, such as the OWASP Top Ten, ensuring coverage against the most common web vulnerabilities.

While a WAF provides strong protection, it is not a panacea. It cannot fix insecure code or prevent all attacks, especially those that exploit logical flaws not covered by its rules. However, combined with secure coding practices, HTTPS, proper authentication mechanisms like OAuth or SSO, and monitoring, a WAF significantly raises the bar for attackers.

Modern WAF features often include rate limiting, bot management, and integration with SIEM systems, providing visibility and automated response to threats. They are particularly valuable for high-traffic applications or services exposed to the public internet, where the volume and diversity of requests make manual inspection impossible.

In short, a WAF is a critical component in web application security: it enforces rules, blocks known attack patterns, and adds a layer of defense to protect sensitive data, infrastructure, and user trust. It does not replace secure design but complements it, catching threats that slip past traditional defenses.

/ˌeɪtʃ-tiː-ɛs-tiː-ɛs/

n. “Never talk unencrypted, even if asked nicely.”

HSTS, short for HTTP Strict Transport Security, is a web security policy mechanism that tells browsers to always use HTTPS when communicating with a specific site. Once a browser sees the HSTS header from a site, it refuses to make any unencrypted HTTP requests for that domain, effectively preventing downgrade attacks and certain types of man-in-the-middle attacks.

Introduced in 2012, HSTS is a response to the persistent problem of users accidentally navigating to HTTP versions of sites or attackers attempting to intercept HTTP traffic and redirect users to malicious endpoints. By enforcing HTTPS strictly, HSTS removes that human and technical error vector.

The policy is communicated via a special response header: Strict-Transport-Security. A typical header might look like this: Strict-Transport-Security: max-age=31536000; includeSubDomains; preload. This tells the browser to enforce HTTPS for one year, apply it to all subdomains, and optionally include the domain in browser preload lists.

For practical purposes, HSTS ensures that once a user visits a site securely, every subsequent visit—even if they type "http://" or click an outdated link—will automatically upgrade to HTTPS. This eliminates the chance of insecure communication slipping in and protects sensitive data like passwords, session cookies, and personal information.

Sites like online banking, e-commerce platforms, and cloud services often implement HSTS in combination with TLS to maximize security. It works hand-in-hand with HTTPS, certificate validation, and other transport-layer security mechanisms.

A subtle but important feature is HSTS preload. Maintained by browsers, this list allows domains to be hardcoded as HTTPS-only, preventing the first connection from ever occurring over HTTP. Domains must meet specific criteria—valid certificates, redirect from HTTP to HTTPS, and correct header configuration—to be added to this list safely.

Misconfiguration can backfire. If a domain deploys HSTS but later mismanages its certificates, users can be locked out because browsers refuse HTTP fallbacks. Planning, monitoring, and automation are crucial.

In short, HSTS enforces a strict policy: encrypted communication only, no exceptions, no shortcuts. It strengthens HTTPS adoption and ensures that even naive users remain protected against some of the most common web-layer attacks. Once deployed properly, it is a silent but formidable guardian of modern web security.

/ˌɛs-ɛf-ti-ˈpi/

n. “Securely moving files without looking over your shoulder.”

SFTP, short for SSH File Transfer Protocol or sometimes Secure File Transfer Protocol, is a network protocol that provides secure file transfer capabilities over the SSH (Secure Shell) protocol. Unlike traditional FTP, which sends data in plaintext, SFTP encrypts both commands and data, ensuring confidentiality, integrity, and authentication in transit.

Conceptually, SFTP looks like FTP: you can list directories, upload, download, delete files, and manage file permissions. But under the hood, all traffic is wrapped in an encrypted SSH session. This eliminates the need for separate encryption layers like FTPS while preventing eavesdropping and man-in-the-middle attacks.

A typical SFTP workflow involves connecting to a remote server with a username/password or SSH key, issuing commands like get, put, or ls, and transferring files through the secure channel. Clients like FileZilla, WinSCP, and command-line sftp utilities are commonly used to interact with SFTP servers.

SFTP is widely used for secure website deployment, backing up sensitive data, or exchanging large files between organizations. For example, a development team may deploy new web assets to a production server using SFTP, ensuring that credentials and content cannot be intercepted during transfer.

The protocol also supports advanced features like file permission management, resuming interrupted transfers, and atomic file operations. Because it operates over SSH, SFTP inherits strong cryptographic algorithms, including AES and HMAC, for encryption and authentication.

While SFTP is similar in appearance to FTP, it is a completely different protocol and is often preferred whenever security and compliance are concerns, such as for GDPR or CCPA regulated data transfers.

SFTP is not just FTP over SSH; it’s a purpose-built, secure protocol that keeps files safe in transit while offering the same flexibility that made FTP useful for decades.

/ˌɛf-ti-ˈpi/

n. “Moving files, one connection at a time.”

FTP, short for File Transfer Protocol, is one of the oldest network protocols designed to transfer files between a client and a server over a TCP/IP network. Dating back to the 1970s, it established a standardized way for computers to send, receive, and manage files remotely, long before cloud storage and modern APIs existed.

Using FTP, users can upload files to a server, download files from it, and even manage directories. Traditional FTP requires authentication with a username and password, although anonymous access is sometimes allowed. Secure variants like SFTP and FTPS encrypt data in transit, addressing the original protocol’s lack of confidentiality.

A basic FTP session involves connecting to a server on port 21, issuing commands like LIST, RETR, and STOR, and transferring data over a separate data connection. While this architecture works, it can be blocked by firewalls or NAT devices, leading to the development of passive FTP and more secure alternatives.

Despite its age, FTP remains in use for legacy systems, website deployments, and certain enterprise workflows. Modern developers may prefer HTTP or SFTP for file transfers, but understanding FTP provides historical context for networked file sharing, permissions, and protocol design.

Example usage: uploading website assets to a hosting server, downloading datasets from a remote repository, or syncing files between office systems. FTP clients like FileZilla, Cyberduck, and command-line tools remain widely deployed, proving the protocol’s resilience and longevity.

FTP does not inherently encrypt credentials or files. When security matters, combine it with secure tunnels like SSH or use its secure alternatives. Its legacy, however, lives on as a foundational protocol that influenced modern file-sharing standards.

/ˌɛks-ɛm-ɛl-ˌhɪt-ti-pi rɪˈkwɛst/

n. “Old school, but still gets the job done.”

XMLHttpRequest, often abbreviated as XHR, is a JavaScript API that enables web browsers to send HTTP requests to servers and receive responses without needing to reload the entire page. Introduced in the early 2000s, it became the backbone of what we now call AJAX (Asynchronous JavaScript and XML), allowing dynamic updates and interactive web applications.

Despite the name, XMLHttpRequest is not limited to XML. It can handle JSON, plain text, HTML, or any type of response. A typical request looks like:

const xhr = new XMLHttpRequest();
xhr.open('GET', '/api/data', true);
xhr.onload = function() {
  if (xhr.status === 200) {
    console.log(JSON.parse(xhr.responseText));
  }
};
xhr.send(); 

Here, open sets up the HTTP method and URL, onload handles the response, and send dispatches the request. Errors and progress events can also be monitored using onerror and onprogress handlers, providing fine-grained control over network communication.

XMLHttpRequest has largely been superseded by the fetch API in modern development, which offers a cleaner, promise-based approach and improved readability. However, XHR remains relevant for legacy applications, older browsers, and cases where fine-grained event handling or synchronous requests are needed.

In practical terms, XMLHttpRequest enabled a shift from static, page-reloading websites to dynamic web apps, laying the foundation for single-page applications (SPAs) and real-time data updates that we take for granted today. Its design influenced modern APIs like fetch, and understanding XHR is essential for maintaining or interfacing with older web systems.

/fɛtʃ/

v. “Go get it — straight from the source.”

fetch is a modern JavaScript API for making network requests, replacing older mechanisms like XMLHttpRequest. It provides a clean, promise-based interface to request resources such as HTML, JSON, or binary data from servers, making asynchronous operations much more readable and manageable.

At its simplest, fetch('https://api.example.com/data') sends a GET request to the specified URL and returns a Promise that resolves to a Response object. This response can then be converted into JSON via response.json() or plain text via response.text(). For example:

fetch('https://api.example.com/users')
  .then(response => response.json())
  .then(data => console.log(data)); 

fetch supports all standard HTTP methods: GET, POST, PUT, PATCH, DELETE, etc., and allows customization through headers, body content, credentials, and mode (such as cors or no-cors). This flexibility makes it ideal for interacting with REST APIs or modern web services.

Unlike curl or older XMLHttpRequest approaches, fetch leverages JavaScript Promises, which allows for straightforward chaining, error handling, and asynchronous logic without the callback hell that plagued older methods. Errors like network failures or server rejections can be caught cleanly with .catch().

fetch also supports streaming responses, enabling partial processing of data as it arrives, which is useful for large files, live feeds, or progressive data consumption. Combined with JSON parsing and modern ES6 features, it provides a robust, readable way to interact with the network directly from the browser or JavaScript runtime environments like Node.js.

In practice, using fetch can simplify web application development, improve maintainability of API calls, and allow developers to handle network operations in a predictable, elegant way. It has become the default method for network requests in modern front-end development, and understanding it is crucial for any developer working with the web today.

/kərl/

n. “Talk to the internet without a browser.”

cURL is a command-line tool and library (libcurl) for transferring data with URLs. It supports a vast array of protocols, including HTTP, HTTPS, FTP, SMTP, and more, making it a Swiss Army knife for internet communication and scripting.

At its core, cURL allows users to send requests to remote servers and retrieve responses. For example, curl https://example.com fetches the HTML of a web page, while curl -X POST -d "name=Chris" https://api.example.com/users can submit data to an API endpoint. This makes it invaluable for testing, automation, and interacting with REST APIs.

cURL is also scriptable and works in batch operations, allowing repeated requests or data fetching without manual intervention. It can handle authentication headers, cookies, and SSL certificates, bridging the gap between human-readable browsing and programmatic interactions.

Developers often pair cURL with JSON or XML responses to automate tasks, test endpoints, or debug network interactions. For example, extracting user data from an API or sending log files to a remote server can be accomplished seamlessly.

While simple in its basic form, cURL is powerful enough to act as a full-fledged HTTP client. It is available on most operating systems, embedded in scripts, CI/CD pipelines, and even used by SaaS platforms to test and integrate external services.

Understanding cURL equips anyone dealing with networking, web development, or automated workflows to interact with the internet directly, bypassing browsers and GUIs, providing precision and reproducibility for testing, troubleshooting, and data transfer.