Developer terms, in plain English

Serving two or more variants of a page or element to different segments of traffic and measuring which drives a target action.

You run two versions of a page to see which converts better, then keep the winner. The catch: you need enough traffic for the result to actually mean something.

The portion of a page visible in the viewport before any scrolling, which varies by device and screen size.

Everything a visitor sees before they scroll. Prime real estate, but it is not one fixed size anymore because phones and laptops differ, so "put it above the fold" is a goal, not a measurement.

Building interfaces usable by people with disabilities, following WCAG guidance for contrast, keyboard navigation, semantics, and screen-reader support.

Making the site usable for people with disabilities (screen readers, keyboard-only, low vision). It is the right thing to do, it widens your audience, and in many places it is a legal requirement.

Optimizing content and structure so AI answer engines (AI Overviews, ChatGPT, Perplexity) can extract and cite it.

Making sure AI assistants mention and cite you when they answer questions, not just ranking blue links. The newer sibling of SEO, and increasingly where the attention is going.

An AI system that can take actions through tools or APIs to accomplish a goal, not just generate text, often looping until a task is complete.

AI that can actually do things, not just chat. Instead of answering a question, an agent can pull a report, update a record, or draft and file content on your behalf.

A text alternative for an image, read by screen readers and used by search engines when the image cannot render.

A short written description of an image. It makes your site accessible, gives Google another signal, and shows up if the image fails to load. A quick, free SEO and accessibility win.

The collection and reporting of user behavior data (pageviews, events, conversions) via tools like GA4 or server logs.

The data on what visitors actually do: where they come from, what they click, where they drop off. The difference between guessing and knowing.

A link that targets a specific element on a page using a URL fragment, scrolling the user straight to it.

A link that jumps to a specific spot on a page, like a table of contents entry. Great for long pages and sometimes earns those indented "jump to" links in Google.

A defined contract that lets one piece of software request data or actions from another over a network, typically returning structured data like JSON.

The way two systems talk to each other. When your site shows live inventory or pushes a form into your CRM, an API is doing the handoff. "Is there an API?" means "can we connect this to that?"

A secret credential that authenticates and authorizes requests to an API, and must be kept out of public code.

A password that lets one tool use another. It must stay secret, which is why developers never want it pasted into email, docs, or the front end of the site.

Verifying who a user is, typically via credentials, tokens, or a third-party identity provider.

Proving you are who you say you are. The login step. It answers "who is this?"

Determining what an authenticated user is allowed to do or see, enforced through roles or permissions.

What a logged-in user is allowed to do. Authentication is "who are you"; authorization is "okay, but can you see the admin dashboard?"

The server-side layer: application logic, databases, and APIs that the user never sees directly.

The engine room. Everything that happens behind the scenes (data, logic, integrations) that the visitor never sees but absolutely feels when it breaks.

The prioritized list of work (features, fixes, tasks) that has not yet been scheduled into active development.

The master to-do list. "It is in the backlog" means it is written down and prioritized, not that someone is working on it right now.

A parallel line of development in version control that isolates changes until they are reviewed and merged.

A safe sandbox copy of the code where new work happens without touching the live site, until it is ready to be combined back in.

A navigational trail showing a page's position in the site hierarchy, often marked up with structured data.

The little "Home > Services > This Page" trail near the top. It helps visitors orient themselves and can show up in Google results under your link.

A screen-width threshold at which the layout changes to adapt to the device, defined in CSS.

The screen width where the design reshuffles for a different device. It is why the site looks one way on desktop and rearranges on a phone.

The client software that requests, renders, and runs web pages; Chrome, Safari, Firefox, and Edge are the major engines.

The app people use to view your site. "It works in Chrome but not Safari" is a real problem, which is why cross-browser testing exists.

A defect where software behaves differently than intended or specified.

Something that is broken or behaving wrong. Worth knowing: a bug is "it does not work as built," which is different from "it works, but I want it to do something else" (that is a new request).

The process of compiling and bundling source code into optimized files ready to be deployed and served.

Packaging the code into the finished version that actually goes live. "The build failed" means the site could not be assembled, so nothing new ships until it is fixed.

Temporarily storing a computed or fetched result so repeat requests are served faster without redoing the work.

A saved copy that makes things load fast. The flip side: if you updated the site and still see the old version, the cache is probably showing you yesterday. "Clear your cache" usually fixes it.

A link element that tells search engines which URL is the authoritative version of near-duplicate pages, consolidating ranking signals.

A note to Google saying "this is the real version of this page." It stops several similar URLs from competing with each other and splitting your SEO value.

A geographically distributed network of servers that caches and serves static assets from a location near the user.

A global network that stores copies of your site close to visitors so it loads fast whether someone is in New York or Nairobi.

A conversational interface, increasingly LLM-powered, that answers questions or performs tasks through chat.

An automated chat assistant on your site or app. Modern AI ones can genuinely understand and help instead of firing canned replies, but only when built on your real content.

An automated pipeline that tests and integrates code changes (CI) and then releases them to an environment (CD).

The automated assembly line that checks new code and pushes it live safely. It is why good teams can ship small improvements often instead of scary big launches.

Software that lets non-developers create, edit, and manage site content without touching code; examples include WordPress and Sanity.

The dashboard where you edit pages, posts, and images yourself without emailing a developer. WordPress is the famous one.

A saved snapshot of changes in version control, with a message describing what changed and why.

A saved checkpoint in the code history, with a note. It is how devs can see exactly what changed, when, and roll back if needed.

A reusable, self-contained piece of UI (a button, card, nav bar) that can be composed into pages.

A reusable building block of the interface. Build the "pricing card" once, reuse it everywhere, and update it in one place. This is why consistent design is also cheaper to maintain.

The maximum amount of text, measured in tokens, a model can consider at once, including both the prompt and its response.

How much an AI can hold in its head at one time. Exceed it and it forgets the start of the conversation, which is why very long documents sometimes have to be fed in chunks.

A small piece of data a site stores in the browser to persist state like sessions, preferences, or tracking identifiers.

A small file the browser keeps so the site remembers you (logged in, items in cart) or so analytics and ads can track behavior. The reason you see consent banners everywhere.

Google's set of user-experience metrics: LCP (loading), INP (interactivity), and CLS (visual stability), used as a ranking signal.

Google's report card for how fast and stable your pages feel. Pass it and you get a ranking edge; fail it and you are fighting uphill. Three scores: load speed, responsiveness, and layout stability.

A browser security mechanism that controls whether a page can request resources from a different domain.

A browser rule about which sites are allowed to pull data from which. When an embedded widget or integration mysteriously will not load, a CORS setting is a common culprit.

A task scheduled to run automatically at fixed times or intervals on a server.

A robot alarm clock on the server. It runs things on a schedule: nightly reports, weekly syncs, cleaning up old data, without anyone pressing a button.

The language that controls the visual presentation of HTML: layout, color, typography, spacing, and responsiveness.

The styling layer. HTML is the content; CSS is what makes it look like your brand instead of a 1995 term paper.

An organized store of structured data that supports querying, writing, and relationships, such as PostgreSQL or MySQL.

Where all the real data lives: users, orders, submissions, content. When someone says "pull it from the database," they mean the single source of truth behind the site.

The process of locating, diagnosing, and fixing the root cause of a defect.

Detective work to find why something broke. It is often the slow part, because reproducing and locating a bug can take far longer than the actual fix.

The process of releasing a build of the application to a running environment.

Pushing changes live. "We are deploying" means the update is going out to the real website right now.

A documented set of reusable components, tokens, and rules that keep a product visually and behaviorally consistent.

Your brand's official kit of parts: colors, fonts, buttons, spacing, all defined once. It keeps everything consistent and makes new pages faster to build and on-brand by default.

The system that resolves human-readable domain names into the IP addresses of servers.

The internet's phone book. It connects your domain name to the server your site lives on. DNS changes are also why a domain move can take a few hours to spread.

The browser's live, in-memory tree representation of a page that JavaScript reads and manipulates.

The browser's live model of the page that code can change on the fly. It is why a page can update (new items, opened menus) without a full reload.

The human-readable address that maps via DNS to a site's servers, registered through a domain registrar.

Your web address, like yourcompany.com. You rent it yearly from a registrar. Losing or letting it lapse is a genuine emergency, so keep that renewal on autopay.

An uncommon or extreme input or condition that can break logic that works for typical cases.

The weird, rare situation that breaks things: the 400-character company name, the emoji in the form, the user in a different time zone. Handling edge cases is a big part of why "simple" takes longer than expected.

A numeric vector representation of text or media that captures meaning, enabling semantic search and retrieval.

How AI turns your content into numbers that capture meaning, so it can find things by concept, not just keyword. The magic behind "search that actually understands what I meant."

Encoding data so only authorized parties can read it, applied in transit (HTTPS) and at rest (stored data).

Scrambling data so only the right people can read it, whether it is moving across the internet or sitting in a database. Core to trust, privacy, and compliance.

A specific URL in an API that accepts requests and returns a defined response.

A single door into an API. One endpoint might return all blog posts, another might submit a form. "Is there an endpoint for that?" means "is there already a way to get or send this data?"

A distinct instance of the application (local, staging, production) with its own configuration and data.

A separate copy of the site for a specific purpose: one for building, one for testing, one that is live. Keeps experiments away from real customers.

A configuration value (often a secret like an API key) stored outside the codebase and injected at runtime.

A setting or secret key kept out of the code itself, so passwords and API keys never get exposed. It is why "just email me the key" makes a developer wince.

A backup behavior or asset used when the preferred one is unavailable or fails to load.

The plan B the site uses when something is not available, like a default font while the brand font loads. Good fallbacks are why a page still works when one piece hiccups.

The small icon associated with a site, shown in browser tabs, bookmarks, and history.

The tiny logo in the browser tab. Small detail, surprisingly noticeable when it is missing or still the previous brand.

A switch that enables or disables functionality at runtime without a new deployment, enabling gradual rollouts.

An on/off switch for a feature that does not require a new launch. It lets us release to 10% of users, test, and flip it off instantly if something is wrong. Great for safe launches.

Further training a base model on domain-specific examples to specialize its behavior.

Teaching a general AI your specific style or domain by training it on your own examples. More involved than prompting, and worth it when you need consistent, on-brand output at scale.

A structured foundation of code and conventions that accelerates building applications; examples include React, Next.js, and Rails.

A proven starter kit and set of rules developers build on instead of inventing everything from scratch. Choosing one well means faster builds and easier hiring later.

The part of the application that runs in the browser and the user interacts with directly: markup, styling, and client logic.

Everything the visitor actually sees and clicks. The opposite of the backend. "Frontend bug" means something visible is off.

AI that creates new content such as text, images, code, or audio by learning patterns from training data.

AI that produces things (drafts, images, summaries) rather than just analyzing. The umbrella term for tools like ChatGPT and Midjourney.

A distributed version-control system that tracks changes to code over time and enables collaboration.

The tool that records every change to the code so a team can work together, see history, and undo mistakes. GitHub is a popular place to host it.

A popular hosting platform for Git repositories that adds collaboration, code review, and automation.

The most popular place teams store and collaborate on code. Think Google Docs, but for the codebase, with history and review built in.

Constraints and checks that keep an AI system's outputs safe, on-topic, and within policy.

The rules that keep an AI assistant on-brand and out of trouble, so it does not wander off-topic, make promises, or say something embarrassing. Essential before AI goes in front of customers.

When an AI model generates confident but factually incorrect or fabricated output.

When AI makes something up and says it with total confidence. The reason you never publish AI output on fact-sensitive topics without a human check.

A content system that stores content and exposes it via an API, leaving presentation entirely to a separate frontend.

A content dashboard with no fixed design attached. You manage content in one place and it can feed your website, app, and anywhere else at once. Great for brands on multiple channels.

The infrastructure and service that runs your application and serves it to the public internet.

Where your website physically lives and runs so people can reach it. Like rent for your site. Vercel, AWS, and WP Engine are examples.

An urgent, narrowly scoped fix deployed outside the normal release cycle to address a critical issue.

An emergency patch for something broken in production, pushed right now instead of waiting for the next planned release. Reserved for genuine fires.

The markup language that defines the structure and content of a web page.

The skeleton of a page: headings, paragraphs, links, images. The raw content and structure, before CSS makes it pretty.

The process where client-side JavaScript attaches interactivity to server-rendered HTML after it loads.

The moment a fast-loading page wakes up and becomes clickable. If a dev mentions a hydration issue, it usually means a brief flicker or a delay before buttons work.

The process by which search engines store and organize crawled pages so they can appear in results.

Getting your pages into Google's library so they can rank. If a page is not indexed, it literally cannot show up in search, no matter how good it is.

Running a trained model to generate output from input, as distinct from training it.

The AI actually answering, as opposed to being built. Mostly a cost-and-speed term: every answer is an inference you pay for, so volume and speed matter.

A connection between your application and a third-party service, typically via its API or webhooks.

Wiring your site up to another tool: HubSpot, Stripe, Salesforce, Google Analytics. "Can we integrate X?" means "can we make these two talk and share data?"

A numeric label identifying a device or server on a network, which DNS maps domain names to.

The actual numeric address of a server behind your domain name. Mostly a developer concern, but it comes up with hosting moves, email setup, and blocking abuse.

An architecture that pre-renders pages and serves them from a CDN, with dynamic bits handled by APIs.

A modern way of building fast, secure sites by serving pre-built pages from a global network. Translation: quick to load and hard to hack. This site uses the idea.

The programming language of the web that adds interactivity and dynamic behavior in the browser (and, via Node, on servers).

The language that makes pages interactive: menus, sliders, live search, chat widgets. If it moves or responds without reloading, JavaScript is usually behind it.

A lightweight, human-readable text format for structured data, the common language of web APIs.

The standard format systems use to pass data back and forth. You do not need to read it, but when a dev says "it returns JSON," they mean the data is in a clean, usable shape.

A workflow method that visualizes tasks as cards moving across columns (To Do, In Progress, Done) with limits on work in progress.

The board of cards you see in Trello, Jira, or Linear. Tasks move left to right as they progress. It is how you can see at a glance what is being worked on and what is stuck.

The time delay between a request and the start of its response, often network- or server-driven.

Lag. The delay before something responds. High latency feels sluggish even if the thing eventually works, and it quietly kills conversions.

Deferring the loading of offscreen assets (images, components) until they are needed, improving initial load time.

Loading images and content only as a visitor scrolls to them, so the top of the page appears fast. Great for speed, just make sure key hero images are not lazy-loaded.

A Core Web Vital measuring the time until the largest visible content element finishes rendering; target under 2.5s.

How long until the main thing on the page (usually your hero image or headline) actually shows up. A key Google speed score; under 2.5 seconds is the goal.

A neural network trained on large text corpora to predict and generate language; examples include GPT and Claude.

The engine behind tools like ChatGPT and Claude. It predicts text, which is why it is brilliant at drafting and summarizing and also why it sometimes states wrong things confidently.

Infrastructure that distributes incoming traffic across multiple servers to improve reliability and performance.

A traffic cop that spreads visitors across multiple servers so no single one gets overwhelmed. Part of why big sites stay up during a spike.

The developer's own machine acting as a server, typically reached at 127.0.0.1, used to run the app privately.

The private version of the site running on a developer's own computer. "It works on localhost" means it works on their machine but is not live for anyone else yet.

Timestamped records of events and errors emitted by an application, used for monitoring and debugging.

The site's diary of what happened and what went wrong. When something breaks, logs are the first place developers look to figure out why.

A lightweight plain-text formatting syntax that converts to HTML, common for docs and content.

A simple way to format text with symbols (hashes for headings, asterisks for bold) that turns into clean web formatting. Many content tools and AI outputs use it.

An open standard that lets AI models connect to external tools and data sources through a consistent interface.

A standard plug that lets AI assistants safely use your tools and data. It is how your team could ask an AI in Slack to pull a real report from your actual website.

Combining changes from one branch into another in version control, resolving any conflicts.

Combining finished work back into the main codebase. "It is merged" means the change is now part of the real project (and usually headed live soon).

HTML tags in the document head that describe a page to browsers and search engines, including title and meta description.

The behind-the-scenes title and description that show up in Google results and when a link is shared. You do not see them on the page, but they heavily influence clicks.

Code that runs between a request and a response to handle cross-cutting concerns like auth, logging, or redirects.

A checkpoint that every request passes through, used for things like "is this user logged in?" or redirects. Mostly behind the scenes, but it powers personalization and gating.

A structured move of data, content, or a system from one place or schema to another.

Moving a site, its content, or its data from one system to another, like replatforming off WordPress. The risky, detail-heavy part of any rebuild, which is why it is planned carefully.

Removing unnecessary characters from code (whitespace, comments) to reduce file size without changing behavior.

Shrinking the site's code files by stripping out the parts only humans need. Smaller files load faster. One of many quiet speed optimizations.

A high-fidelity visual design of a page or screen, showing final look before it is built.

A polished picture of what a page will look like, before any code. More finished than a wireframe. This is what you approve so there are no surprises at launch.

A model that can process or generate more than one type of input or output, such as text, images, and audio.

AI that handles more than text; it can see images, hear audio, and read documents. It is why you can now paste a screenshot and ask the AI about it.

The smallest version of a product that delivers core value and can be released to learn from real users.

The leanest launchable version: enough to be useful and start learning, without every bell and whistle. The point is to ship, measure, and improve, not to perfect in a vacuum.

Platforms that let users build apps or sites with visual tools and little or no handwritten code.

Tools like Webflow or Zapier that let non-developers build or automate with clicks instead of code. Great for speed and simple needs; they hit limits as things get complex or custom.

A runtime that executes JavaScript outside the browser, commonly used to build servers and tooling.

Technology that lets developers use one language (JavaScript) for both the front and back of a site. Fewer languages, often a faster, more unified team.

An open standard for delegated authorization, enabling "log in with Google/Microsoft" without sharing passwords.

The tech behind "Sign in with Google." It lets users log in through an account they already trust, so you never handle their password. Fewer signup drop-offs, more security.

A metadata protocol that controls how a URL appears when shared on social platforms (title, description, image).

The settings that decide the image and text that appear when your link is pasted into LinkedIn, Slack, or iMessage. Get them right and shares look polished instead of broken.

Software whose source code is publicly available to use, modify, and distribute under a license.

Software that is free to use and publicly built, like WordPress or React. Huge upside and community, but "free" still needs expertise to implement and maintain well.

The actual data carried in a request or response, separate from headers and metadata.

The real contents of a message between systems, the data itself. When a dev asks "what is in the payload?" they mean "what data are we actually sending?"

A packaged piece of functionality that extends a platform like WordPress or a browser without core changes.

An add-on that bolts extra features onto a platform. Fast to add, but too many plugins is a top cause of slow, bloated, and insecure WordPress sites.

The live environment real users interact with, where uptime and data integrity matter most.

The real, live website your customers use. "In production" means it is out in the wild, so mistakes here are visible to everyone.

The input instruction given to an AI model that shapes its output; prompt engineering refines this for reliable results.

What you type to tell an AI what you want. Better prompts get dramatically better results, which is why "prompt skills" are suddenly a real thing marketers invest in.

An attack where crafted input manipulates an AI system into ignoring its instructions or leaking data.

A way people try to trick your AI into misbehaving or revealing things it should not. The reason a public-facing AI needs real guardrails and testing, not just a clever prompt.

A proposal to merge a branch's changes, used for code review and discussion before integration.

A "please review this before it goes in" request between developers. It is the quality gate where another dev checks the work before it is merged.

A website built to behave like a native app: installable, offline-capable, and fast via service workers.

A website that acts like an app: it can be added to a phone's home screen and work offline, without the app store. A lighter alternative to building a native app.

The practice of testing software against requirements to catch defects before release.

The testing step before launch, where someone deliberately tries to break things and confirm they work. Skipping QA is how typos and broken forms reach customers.

A request for specific data from a database or API, often written in a language like SQL.

A question asked of the database, like "all customers who signed up last month." Complex reports are really just carefully written queries.

A buffer that holds tasks or messages to be processed asynchronously, smoothing load and improving reliability.

A waiting line for work the system handles in the background, like sending thousands of emails. It is why a big send does not freeze the whole site.

An AI pattern that retrieves relevant documents and feeds them to a model so answers are grounded in real sources.

A way to make AI answer from your actual content instead of guessing, by fetching the right documents first. The key to a chatbot that cites your real policies and docs, not fiction.

Capping how many requests a client can make in a time window to protect against abuse and overload.

A cap on how often something can be used in a given time, to stop abuse and runaway costs. It is why an API or form may say "too many requests, slow down."

An HTTP response that sends a browser from one URL to another; 301 is permanent, 302 is temporary.

A forwarding rule from an old URL to a new one. Essential when you change page addresses so you do not lose traffic or SEO. Use 301 (permanent) when a page moves for good.

Restructuring existing code to improve clarity or maintainability without changing its external behavior.

Cleaning up the code's plumbing without changing what users see. It feels invisible, but it is what keeps future changes fast and cheap instead of slow and risky.

Turning code and data into the visible page; server-side rendering (SSR) builds HTML on the server, client-side (CSR) in the browser.

How a page gets drawn. Rendering it on the server first (SSR) usually means faster first paint and better SEO than building it all in the browser. A common performance lever.

A project's complete set of files and full version history, tracked in version control.

The project's home folder plus its entire history. "It is in the repo" means it lives in the official codebase.

A design approach where layouts fluidly adapt across screen sizes using flexible grids and breakpoints.

One site that automatically reshapes itself to look right on phone, tablet, and desktop. The alternative (a separate mobile site) is mostly extinct for good reason.

A widely used API style that models data as resources accessed over HTTP methods, usually returning JSON.

The most common style of API. You do not need the details; just know it is a standard, well-understood way for systems to exchange data, which makes integrations more predictable.

A file at the site root that tells crawlers which paths they may or may not access.

A text file that tells search engines and bots where they can and cannot go. Misconfigure it and you can accidentally hide your whole site from Google, so it is handled with care.

Reverting an application to a previous known-good version after a bad release.

The undo button for a launch. If a deploy breaks something, a good setup lets the team roll back to the last working version in minutes.

Software delivered over the web on a subscription, hosted and maintained by the provider rather than installed.

Software you subscribe to and use in the browser, like HubSpot or Figma, instead of installing. The dominant model, and probably how most of your stack already works.

A system's ability to handle growth in traffic or data without degrading performance.

Whether the site can handle a big surge, say a viral moment or a launch, without falling over. "Is it scalable?" means "will this still work when we are ten times bigger?"

Standardized machine-readable data (often JSON-LD) added to pages so search engines and AI can understand entities and relationships.

Hidden labels that explain your content to Google and AI (this is a product, this is the price, this is a review). It helps you earn rich results and get cited by AI answers.

The uncontrolled expansion of a project's requirements beyond what was originally agreed.

When "just one small addition" keeps happening until the project is twice the size and past deadline. Not evil, just unmanaged. The fix is naming new asks as new work.

A packaged set of tools and libraries that makes building on a platform or service easier.

A ready-made toolkit a service provides so developers can integrate it faster. "They have an SDK" usually means an integration will be quicker and more reliable.

Search that matches on meaning using embeddings rather than exact keywords.

Search that understands intent, not just matching words. Someone searches "cheap flights" and still finds "budget airfare." A big upgrade over old keyword-only search.

The practice of improving a site's technical health, content, and authority to rank in organic search.

Everything you do to show up in Google without paying for ads. Part content, part technical, part reputation. The compounding channel that keeps paying off after you stop spending.

A computer or process that receives requests and returns responses, running your application and serving data.

The always-on computer that runs your site and sends pages to visitors. "The server is down" means the site is unreachable, not that your laptop broke.

A server- or token-tracked period of a user's interaction, used to persist login and state across requests.

A single continuous visit. It is how the site remembers you are logged in as you move between pages, and it is a core unit in your analytics ("sessions this month").

A site that loads once and updates content dynamically via JavaScript instead of full page reloads.

A site that feels like an app: you click around and it updates instantly without full reloads. Snappy for users, but needs care so it stays fast and SEO-friendly.

A file listing a site's important URLs to help search engines discover and crawl them efficiently.

A map of your pages handed to search engines so they find everything worth ranking. Especially helpful for large or new sites that Google has not fully explored yet.

The human-readable, URL-safe identifier for a page, usually derived from its title.

The readable end of a web address, like /how-to-talk-to-developers. A clean, keyword-aware slug is a small, free SEO win.

A fixed-length iteration (often one to two weeks) in which a team commits to and completes a set of work.

A short, focused work cycle (usually a week or two) with a committed set of tasks. It is why "we can add that next sprint" is a real answer, not a brush-off.

The standard language for querying and manipulating data in relational databases.

The language used to ask databases questions. When you want a custom report, someone usually writes SQL to pull exactly the slice of data you asked for.

A certificate and protocol that encrypt traffic between browser and server, enabling HTTPS and the padlock icon.

What puts the padlock and the "s" in https. It encrypts data, builds visitor trust, and is required for SEO. A missing or expired certificate scares people off instantly.

A production-like environment used to test changes with realistic data before releasing them live.

A private dress-rehearsal copy of the site that looks and works like the real one, where you preview and approve changes before they go live. Always review on staging, not production.

A numeric code in an HTTP response signaling the outcome: 200 success, 301 redirect, 404 not found, 500 server error.

The number the web uses to say what happened. 404 means the page is missing; 500 means the server broke. Knowing the code tells you instantly whether it is a content problem or a crash.

A prefix on a domain (blog.example.com) that can point to separate content or infrastructure.

A branch off your main domain, like blog.yoursite.com or app.yoursite.com. Useful for separating sections, though where to split content has real SEO implications worth discussing.

The implied future cost of shortcuts or deferred cleanup in a codebase, which slows later work until repaid.

The buildup of quick fixes and shortcuts that make future changes slower and riskier. Like financial debt: a little is fine and strategic, too much and every new feature costs more.

A tracked unit of work (bug, feature, task) in a project-management or issue-tracking tool.

A single tracked task in a tool like Jira or Linear. "Open a ticket" means "log it properly so it is tracked," not "it is being ignored."

The unit of text an LLM processes; a chunk of characters roughly three-quarters of a word, used for context limits and pricing.

How AI measures text, a bit smaller than a word. It matters because AI tools are priced per token and have a limit on how much they can read at once, which affects cost and what you can feed them.

A tiny invisible asset or script that fires to record events like a pageview or conversion for analytics or ads.

The invisible snippet (like the Meta or LinkedIn pixel) that reports visits and conversions back to your ad platforms. The thing powering retargeting and campaign measurement.

An extra verification step beyond a password, such as a code from an app or text, to confirm identity.

The second step after your password, usually a code from your phone. It is one of the single biggest things you can do to keep accounts from getting hacked.

The visual and interactive layer a user touches: layout, controls, and visual design.

What the product looks like, the buttons, screens, and layout. UI is the look; UX is the feel. Good UI is attractive; good UX is effortless.

An automated test that verifies a small, isolated piece of code behaves correctly.

An automated check on a small piece of the code that runs every time something changes. Good test coverage is why some teams can ship fast without constantly breaking things.

The percentage of time a service is available and operational; downtime is the inverse.

How reliably your site stays online, usually quoted as a percentage like 99.9%. Downtime is when it is unreachable, and every minute of it can mean lost leads and sales.

The full address of a resource on the web, including protocol, domain, path, and optional query parameters.

A web address. Clean, readable, keyword-aware URLs help SEO and look trustworthy when shared. The messy ones full of random characters are worth cleaning up.

The overall experience of using a product, including flow, usability, performance, and clarity.

How it feels to actually use the thing: easy or frustrating, clear or confusing. Great UX quietly lifts conversion; bad UX makes even a beautiful site underperform.

A database optimized to store and search embeddings by similarity, powering semantic search and RAG.

A special database that stores content by meaning so AI can find the most relevant pieces fast. The memory behind a smart assistant that actually knows your material.

A system that records changes to files over time so you can review history, collaborate, and revert; Git is the standard.

The time machine for code. It keeps a full history so the team can collaborate safely and undo any change. "Is it in version control?" means "is this properly tracked and recoverable?"

The visible area of a page in the browser, whose size drives responsive layout decisions.

The visible window of the screen, which differs on phone, tablet, and desktop. It is the frame your design has to look good in, whatever device someone is on.

The international standard defining accessibility requirements, with conformance levels A, AA, and AAA.

The official rulebook for accessibility. "WCAG AA" is the level most organizations aim for and that many accessibility laws reference. The yardstick for "is our site compliant?"

A mechanism where one system sends an automatic HTTP request to another when a specified event occurs.

An automatic "it happened" alert between tools. When someone submits a form, a webhook can instantly tell your CRM, Slack, and email tool without anyone lifting a finger.

A self-contained UI element or embeddable third-party component dropped into a page.

A drop-in block of functionality, like a chat bubble, review carousel, or booking box. Convenient, but each one adds weight, so too many can slow the page down.

A low-fidelity structural blueprint of a page focused on layout and hierarchy rather than visual design.

The rough blueprint of a page, boxes and labels, before any colors or polish. It is where you argue about what goes where cheaply, before it is expensive to change.

The most widely used open-source CMS, extensible via themes and plugins, powering a large share of the web.

The most popular website platform in the world. Flexible and familiar, but easy to bloat with plugins and leave insecure if it is not maintained by someone who knows what they are doing.

A structured, tag-based text format for encoding data, used in sitemaps, feeds, and older APIs.

An older cousin of JSON for structured data. You will mostly meet it in XML sitemaps and RSS feeds. Not something you handle directly, just a format you will hear named.

A vulnerability where attackers inject malicious scripts into pages viewed by other users.

A common type of website hack where bad code sneaks in through an input and runs on your visitors. The reason developers are strict about validating anything users submit.

A human-readable data format using indentation, common for configuration files.

A clean, readable format used for configuration and settings files. You will likely only see it named in technical setup, but it is friendlier to read than most config formats.

A CSS property that controls the front-to-back stacking order of overlapping elements.

The setting that decides which element sits on top when things overlap. When a menu hides behind an image or a popup appears underneath the page, a z-index tweak is usually the fix.