Glossary

This site explains itself in public. The credits name every piece of technology behind it, the notes argue about browser bugs, and the conformance claim cites clauses by number — so a reader who follows any of that meets words that are precise and unfamiliar at the same time.

Each one below gets a line. The name links to the people who define it, because a summary is a place to start and a specification is the thing that is true. Where the site has written a longer article about a word, the name opens the article instead, and its further reading starts at that same source.

access control

granting or refusing each request to use a resource

accessibility

a site's fitness for people with disabilities

ACME

the protocol that issues a certificate without a human

alert

a message a system sends when something needs a person

animation

a change in a page's look played out over time

Ansible

a tool that puts a server into a written-down state

API

the described way one program calls another

app

a program people use to get a task done

ArcGIS

Esri's commercial GIS platform

architecture

how a system's parts fit together and why

ARIA

extra markup that names a control for assistive tech

authentication

proof that a request is from who it claims

AWS

Amazon's cloud platform

axe

the accessibility engine this site is audited with

Azure

Microsoft's cloud platform

backend

the half of a system the reader never loads

backup

a copy of data against loss, and the making of it

Bash

the GNU shell most scripts are written for

Bicep

Azure's own language for declaring infrastructure

BigQuery

Google's warehouse for querying very large tables

blue-green deployment

switching live traffic between two identical environments

business intelligence

turning a business's data into reports that guide decisions

button

a control a person presses to make something happen

cache

a stored copy a browser may reuse instead of asking

caching

keeping an answer so the work is not repeated

canary release

releasing a change to a small share of users first

canonical URL

the one address a page says is its own

CDN

servers near the reader that hand out copies

change data capture

reading the changes made in a database and passing them on

chaos engineering

controlled experiments that inject failure into production

CI

merging work at least daily, each merge proven by a build

CIDR

a way to write and route address blocks of any size

CLDR

Unicode's data on each locale's dates, numbers and sorting

cloud

computing rented by the hour from somebody else

code review

another person examining a change before it is merged

codebase

all the source code of one app, kept in one repository

computer file

a named set of data stored as one unit

configuration

the settings that decide how a system behaves

connection pool

a set of open database connections kept ready for reuse

container runtime

the program that actually starts a container

Content Security Policy

a list of where a page may load things from

contrast ratio

how far apart two colours are, as a number

cookie

a small value a site asks the browser to keep

Core Web Vitals

three measurements of how a page feels to use

CORS

how a server lets pages on other origins read its responses

crawler

a program that fetches pages to index them

cron

the Unix scheduler that runs the commands in a crontab

cross-site scripting

an attack that gets a page to run an attacker's script

CSRF

an attack that tricks a browser into an unwanted request

CSS

the language that says how a page looks

CTE

a named subquery a bigger query reads as a table

CVE

the public list giving each disclosed vulnerability one ID

daemon

a program that runs in the background, unattended

dashboard

one screen built to answer a recurring question

data analytics

processing data systematically to find patterns and trends

data lake

a store that keeps raw data in its original form

data mesh

domain teams serving their analytical data as products

data storage

keeping data, or the media that hold it, for later reading

data warehouse

a database that gathers a business's data for analysis

database

a store of data organised so that programs can query it

database index

a structure that finds table rows without a full scan

database normalization

arranging tables so each fact is stored once, under its key

dataset

a collection of data published as one unit

defect

a flaw that keeps a product from meeting its requirements

deployment

moving a change to where people actually use it

DevOps

practices that join software development and operations

DHCP

a protocol that leases IP addresses and settings to devices

disaster recovery

getting service back after a major loss, by a tested plan

Django

a Python framework for building web applications

DNS

the directory turning a name into an address

Docker

a way to ship a program with everything it needs

DOM

the live tree of objects a browser builds from a page

downtime

the stretch where a service answers nobody

email

mail sent between mailboxes across the internet

encryption

making data unreadable without the key

end-to-end test

a test that drives the whole system the way a user does

error budget

the share of failures a reliability target still allows

ESLint

a rule-driven linter for JavaScript

ETL

moving data between systems, reshaping it on the way

event sourcing

keeping state as the ordered log of events that changed it

exponential backoff

a retry pause that multiplies after every failure

favicon

the small picture a browser shows beside a page

feature flag

a switch that turns code on or off without a new deploy

feed

a page's updates, in a format you subscribe to

file system

the structure that turns a disk into named files and folders

firewall

the rule set that decides which traffic passes

font

a typeface in a file the page downloads

forge

a web platform where code is hosted, reviewed and shared

frontend

the half of a system that runs in the reader's browser

full-text search

searching documents by their words, ranked by relevance

GDAL

the library that reads every geospatial format

Gemini

a lightweight internet protocol for serving hypertext

gemtext

a text format with one link per line

GeoJSON

geography written as JSON

geospatial

data whose meaning depends on where it is

GIS

systems for data that has a place on a map

git

the version control this site's history lives in

git hook

a script git runs when something happens

GitHub

Microsoft's hosting for git repositories

GitLab

a git platform you can also run yourself

GitOps

running infrastructure from a desired state kept in Git

Go

a compiled, strongly typed, garbage-collected language

Google Cloud

Google's cloud platform

Gopher

a menu protocol older than the web

Grafana

a dashboard tool for metrics and logs

GraphQL

a query language in which the client picks the fields

gRPC

a framework for calling remote procedures over HTTP/2

hardening

removing what an attacker could use

hardware

the physical parts of a computer

health check

an automated test of whether a service is working

high availability

the ability of a service to keep running when a part fails

host

a computer attached to a network

hreflang

the attribute pairing a page with its translations

HSTS

a browser's promise to use HTTPS next time

HTML

the language a page's structure is written in

HTTP

the request and answer the web is built on

HTTPS

the same requests, over an encrypted connection

idempotent

safe to run twice, because the second time changes nothing

immutable infrastructure

replacing servers instead of changing them in place

incident

an event that puts a system's data or service at risk

information security

protecting data and systems from misuse and harm

infrastructure as code

managing infrastructure from versioned definition files

internationalization

designing software so that it can easily be localized

IP address

a number that tells the network where to deliver a packet

IPv6

the version of the Internet Protocol with 128-bit addresses

JavaScript

the language browsers run

JSON

the text format most data travels in

JSON Schema

a language for describing the shape of JSON data

JWT

a compact, URL-safe token that carries claims as JSON

kernel

the core of an operating system

Kubernetes

a system that keeps a fleet of containers running

landmark

a region of a page a screen reader can jump to

large language model

a neural network trained on text to predict the next token

latency

the wait between asking and the first of the answer

lazy loading

loading something only when it is first needed

Leaflet

a small library for maps in a browser

library

code packaged for other programs to call

Lighthouse

Chrome's own audit of speed, markup and good practice

linter

a tool that flags likely bugs in code without running it

Linux

the kernel most servers run on

load balancer

a server that spreads requests across several others

load test

a test that measures a system under simulated traffic

localization

adapting software to one market's language and conventions

logging

writing down what happens, as it happens

machine learning

building software that learns a task from examples in data

macOS

Apple's desktop operating system

Mapbox

a commercial source of map tiles and styles

Markdown

plain text with a few marks that mean formatting

materialized view

a view that stores the result of its query like a table

metadata

the data describing other data, so it can be found

metrics

numbers a system reports about itself

microservices

an architecture of small services, each deployed on its own

migration

a planned move to a new version or platform

monitoring

watching a running system so it tells you first

multi-factor authentication

sign-in that needs two or more different kinds of proof

NAT

the rewriting of IP addresses as packets pass a router

network server

a computer or program that serves others over a network

Next.js

a React framework for building web apps

nginx

a web server and reverse proxy

OAuth

a way to give an app limited access without a password

observability

understanding a system from the outside, from what it emits

onion service

an address that works only through Tor

OpenAPI

a machine-readable description of an HTTP API

OpenID Connect

an identity layer on top of OAuth for signing users in

OpenTelemetry

one vendor-free way to send telemetry

operating system

the software that manages hardware for every other program

operational secret

a credential a program needs, like a key or a password

ORM

a library that maps database tables to objects in code

package

code bundled with a description, ready to install

partitioning

splitting one table into physical pieces

password

a secret string that proves who is signing in

penetration test

an authorised attack that shows which flaws can be exploited

PHP

the language most of the old web runs on

pipeline

a run of steps carrying data from source to use

Playwright

the tool that drives a browser in tests

Podman

a container engine that needs no daemon

port

the number that picks a service on a host

PostGIS

the extension that gives PostgreSQL geometry

PostgreSQL

the database most of this work was built on

postmortem

a written review of an incident, made to stop it recurring

privilege

a right a system grants to a person or process

progressive enhancement

building pages that work in plain HTML, then adding more

progressive web app

a website that can be installed and run like an app

Prometheus

a database that scrapes and stores metrics

protocol

the agreed rules two programs follow to talk

proxy

a server that forwards a request on your behalf

Python

the language most of this site's tooling is in

QGIS

the free desktop GIS

quality gate

a set of checks code must pass before it moves on

query

a written question a database answers

queue

work left in order for something else to pick up

RAID

several disks run as one, usually so one can fail safely

rate limiting

a cap on how many requests a client may send per interval

RBAC

permissions granted to a role, not a person

Redis

an in-memory store for things that live briefly

refactoring

changing code's structure without changing what it does

regular expression

a pattern that describes which strings count as a match

replication

keeping copies of a database in step on other servers

repository

a store that keeps saved versions of a set of files

responsive design

a layout that adapts to whatever screen it is read on

REST

the web's architectural style, built around resources

retrieval-augmented generation

generating answers from documents retrieved per question

robots.txt

the file telling crawlers where not to go

RSS

the older of the two XML formats a feed is written in

Ruff

a fast linter and formatter for Python

Rust

a compiled language that checks memory for you

S.M.A.R.T.

a disk's built-in self-check that warns of coming failure

scalability

whether more load needs more than more machines

schema

a named group of tables inside one database

screen reader

software that reads a page aloud, or into braille

semantic versioning

a version-number scheme that signals breaking changes

SEO

making a page findable without paying for it

server-sent events

a one-way stream of events from a server over HTTP

server-side rendering

producing a page's HTML on the server for each request

serverless

running code without managing the servers it runs on

service level objective

a measurable reliability target that a service must meet

service worker

a script that answers requests when the network cannot

single-page application

a web app that loads one page and changes it with JavaScript

sitemap

a list of a site's pages, written for machines

software

the programs and data a computer runs

SQL

the language relational databases answer

SQL injection

an attack that turns input into part of a database query

SQL Server

Microsoft's relational database

SQLite

a whole database in a single file

SSH

an encrypted shell on another machine

SSRF

an attack that makes a server fetch a URL the attacker chose

star schema

a layout with one fact table and dimension tables around it

static site generator

a program that writes every page out in advance

structured data

facts about a page, written for machines

stylesheet

the file that holds a page's CSS

Subresource Integrity

a hash a browser checks a file against

SVG

an XML language for drawing graphics that scale

systemd

the thing that starts everything else on Linux

technical debt

the extra cost later of a quick, expedient choice made now

Terraform

HashiCorp's tool that plans and applies infrastructure code

test-driven development

writing the test before the code, one small test at a time

TLS

the handshake that encrypts a connection

Tor

a network that routes traffic through volunteer relays

transaction

a group of database changes that succeed or fail as one

TypeScript

JavaScript with types checked before it runs

Ubuntu

a Linux distribution common on servers

UI

the part of a program a person sees and works with

Unicode

the standard that gives every character a number of its own

unit test

an automated check of one small piece of code in isolation

URL

the address that says where a thing is

user

a person, or a process acting for one, allowed into a system

UTF-8

the Unicode encoding with one to four bytes per character

validation

checking input against the rules before trusting it

vector search

finding stored items whose vectors lie closest to a query

viewport

the part of a page a window actually shows

virtual machine

a whole computer run in software on a physical host

VPN

a private network carried over a public one

WCAG 2.2

the accessibility standard this site is held to

web app manifest

the file that lets a site be installed

web browser

the program a person uses to open web pages

web components

browser features for defining new, reusable HTML elements

WebAssembly

a portable binary code format that runs in a sandbox

webhook

an HTTP request a service sends when an event happens

WebP

an image format smaller than the ones it replaces

website

a set of related web pages under one address

WebSocket

a protocol for a two-way connection that stays open

WordPress

the CMS most of the web is published with

YAML

a format for settings a person can still read

zero trust

a model that grants no trust on network location alone