Glossary

12-Factor App

Twelve-Factor Application

A methodology of twelve best practices for building scalable, maintainable software-as-a-service applications.

2FA

Two-Factor Authentication

A security process requiring two distinct forms of identification — typically a password and a code from a separate device.

301 Redirect

301 Permanent Redirect

An HTTP status code permanently redirecting one URL to another, transferring most link equity to the new URL.

AAC

Advanced Audio Coding

A lossy audio codec designed as the successor to MP3, offering better quality at similar bitrates.

ABR

Adaptive Bitrate Streaming

A streaming technique that dynamically adjusts video quality based on the viewer's network conditions.

A/B Testing

A/B Split Testing

Comparing two versions of content by showing each to a random subset of users to determine which performs better.

Accessibility

Design Accessibility (a11y)

Designing products usable by people with disabilities, following WCAG guidelines for perceivable and operable interfaces.

AcroForm

Acrobat Form Technology

The standard interactive form technology in PDF documents, supporting text fields, checkboxes, radio buttons, and digital signatures.

AES

Advanced Encryption Standard

A symmetric block cipher used worldwide for encrypting sensitive data, with key sizes of 128, 192, or 256 bits.

Affordance

Design Affordance

A visual cue suggesting how an element should be used (e.g. a raised button affords clicking).

AIFF

Audio Interchange File Format

An Apple-developed uncompressed audio format similar to WAV, commonly used in professional audio on macOS.

Algorithm (Social)

Social Media Algorithm

A ranking system that determines which content appears in a user's feed based on engagement signals, relevance, and recency.

Aliasing (Audio)

Audio Aliasing

Distortion occurring when audio frequencies above the Nyquist limit are sampled, producing false lower frequencies.

Alignment Pattern

QR Code Alignment Pattern

Smaller square patterns in larger QR codes that help correct distortion when scanning at an angle.

Alpha Channel

Alpha Channel (Transparency Mask)

An alpha channel stores transparency information for each pixel in an image, with values ranging from fully transparent to fully opaque. It is the fourth channel in RGBA color, enabling smooth blending of images over backgrounds.

Alpha Compositing

Combining semi-transparent images by blending pixel colors according to their alpha channel values.

Alt Text

Image Alternative Text

A text description of an image for accessibility and SEO, displayed when the image cannot be loaded.

Analogous Colors

Analogous Color Scheme

Three or more colors adjacent on the color wheel, producing harmonious and visually cohesive palettes.

Anchor Positioning

CSS Anchor Positioning

A layout feature that positions elements relative to a named anchor element, useful for tooltips and popovers.

Anchor Text

Link Anchor Text

The visible clickable text of a hyperlink, providing context to search engines about the linked page's topic.

Annotation

PDF Annotation

A markup element added to a PDF page, such as highlights, comments, stamps, or drawing shapes.

API

Application Programming Interface

A set of protocols and tools enabling different software applications to communicate with each other.

API Gateway

A server that acts as a single entry point for API requests, handling routing, authentication, and rate limiting.

APNG

Animated Portable Network Graphics

An extension of PNG supporting animated images with full alpha transparency, superior to GIF's 256-color limit.

Archive

File Archive

A single file that bundles multiple files and directories together, optionally with compression, for storage or transfer.

Argon2

Argon2 Key Derivation Function

The winner of the Password Hashing Competition, designed to be memory-hard and resistant to GPU cracking attacks.

ARIA

Accessible Rich Internet Applications

A set of HTML attributes that define roles, states, and properties for UI elements, making dynamic content accessible to assistive technologies.

Arrow

Apache Arrow

A cross-language columnar memory format for flat and hierarchical data, enabling zero-copy reads for analytics.

ASCII

American Standard Code for Information Interchange

A 7-bit character encoding standard representing 128 characters including English letters, digits, and control codes.

Aspect Ratio

Aspect Ratio (Width-to-Height Proportion)

Aspect ratio is the proportional relationship between an image's width and height, expressed as two numbers separated by a colon. Common ratios include 16:9 (widescreen), 4:3 (classic), and 1:1 (square).

Aspect Ratio (CSS)

CSS aspect-ratio Property

A property that sets a preferred width-to-height ratio for an element, preventing layout shift during loading.

AST

Abstract Syntax Tree

A tree representation of the syntactic structure of source code, used by compilers and code analysis tools.

Audio Codec

Software that encodes raw audio into a compressed format and decodes it back for playback (e.g. MP3, AAC, FLAC).

Audio Fingerprint

Acoustic Fingerprinting

A compact digital summary of an audio signal used to identify songs or detect duplicate content.

Audio Watermark

Audio Watermarking

Embedding imperceptible identifying data into an audio signal for copyright tracking and content identification.

AV1

AOMedia Video 1

A royalty-free video codec offering 30-50% better compression than H.265, developed by the Alliance for Open Media.

AVIF

AV1 Image File Format

A next-generation image format based on the AV1 video codec, offering superior compression.

AVIF Sequence

AVIF Image Sequence

An animated image format using AVIF's AV1 compression, offering dramatically smaller files than GIF or APNG.

Aztec Code

Aztec Barcode

A 2D barcode with a bullseye finder pattern in the center, used on airline boarding passes and transit tickets.

Backlink

Inbound Backlink

A hyperlink from one website to another, used by search engines as a signal of content authority and trust.

Backpressure

Stream Backpressure

A flow control mechanism where a slow consumer signals a fast producer to reduce its output rate, preventing buffer overflow.

Base58

Base58 Encoding

A binary-to-text encoding that excludes visually ambiguous characters (0, O, I, l), used in Bitcoin addresses.

Base64

Base64 Encoding

A binary-to-text encoding scheme that represents binary data as ASCII characters.

Baseline Grid

Typographic Baseline Grid

A horizontal grid aligned to text baselines that maintains consistent vertical rhythm across a page.

Batch Processing

Batch File Processing

Processing multiple files simultaneously using the same operation, saving time on repetitive tasks.

Batch Resize

Batch Image Resize

Processing multiple images at once to change their dimensions to a uniform size or percentage of the original.

Bates Numbering

A sequential numbering system used in legal documents for identification and retrieval.

Bayes' Theorem

A formula for updating the probability of a hypothesis given new evidence, foundational to statistical inference.