Glossary

Technical terms used across ToolHub tools and learning content.

AESAES is a symmetric block cipher standard used with a mode of operation such as GCM or CBC to encrypt data with a shared key.
APIAn API is a documented contract that lets one program call another, most commonly over HTTP with JSON request and response bodies.
ASCIIASCII is a 128-character encoding covering unaccented Latin letters, digits, punctuation, and control codes, using one byte per character.
Base64Base64 encodes bytes as ASCII text using a 64-character alphabet. It is reversible encoding, not encryption, and expands data by roughly one third.
BinaryBinary is base-2 notation using only 0 and 1, matching how hardware stores data and making individual bit positions directly visible.
Canonical URLA canonical URL is the preferred address for a page, declared with a link tag so duplicate variants consolidate their ranking signals.
ChecksumA checksum is a short value computed from data to detect accidental corruption during storage or transfer, usually a hash digest in practice.
CipherA cipher is an algorithm that transforms plaintext into ciphertext and back using a key, unlike an encoding, which requires no key at all.
Compound interestCompound interest applies interest to accumulated interest as well as the principal, so growth depends on both the rate and the compounding frequency.
Content Security PolicyContent Security Policy is a response header that restricts which scripts, styles, and other resources a page may load, limiting injection damage.
Contrast ratioContrast ratio compares the relative luminance of two colors on a scale from 1:1 to 21:1, and it determines whether text on a background is legible.
Cron expressionA cron expression schedules recurring work using five fields—minute, hour, day of month, month, and day of week—interpreted against wall-clock time.
CSS gradientA CSS gradient paints a smooth transition between two or more color stops without an image request, along a line or from a point.
CSVCSV stores tabular data as delimited text rows, with quoting rules for fields that contain the delimiter, quotes, or line breaks.
EntropyEntropy measures unpredictability in bits: the base-two logarithm of how many equally likely values a secret could have taken.
Epoch timeEpoch time counts elapsed seconds since 1 January 1970 UTC, giving an unambiguous instant with no timezone attached.
HashA cryptographic hash maps input to a fixed-length digest. Hashes are one-way fingerprints used for integrity checks—not encryption and not a substitute for password storage without a proper KDF.
HEX colorA HEX color writes red, green, and blue channels as two hexadecimal digits each, optionally with two more digits for alpha transparency.
HexadecimalHexadecimal is base-16 notation where each digit represents exactly four bits, making it the compact standard for bytes, colors, and masks.
HMACHMAC is a keyed hash construction that proves a message was produced by someone holding a shared secret, not merely that the bytes are intact.
HSLHSL describes color as hue, saturation, and lightness, which makes generating tints, shades, and hover states far easier than adjusting RGB channels.
HTML entityAn HTML entity represents a character using a named or numeric reference, letting markup-significant characters appear as literal text.
HTTP headerAn HTTP header is a name-and-value pair carrying metadata about a request or response, such as content type, caching rules, or authentication.
JSONJSON (JavaScript Object Notation) is a text format for objects, arrays, and primitive values. It is the default interchange format for many HTTP APIs and browser apps.
JWTA JWT is a compact token with Base64url-encoded header, payload, and signature segments. Decoding reveals claims; verification requires cryptographic checks in your auth stack.
Lossy compressionLossy compression discards information the viewer is unlikely to notice in exchange for a much smaller file, and the discarded detail cannot be recovered.
MedianThe median is the middle value of an ordered dataset, making it resistant to outliers that would drag the mean away from the typical case.
Meta descriptionA meta description is the summary a page offers for search result snippets, usually around 150–160 characters before truncation.
MinificationMinification removes optional whitespace and formatting from a document so it transports in fewer bytes while parsing to the same value.
Open GraphOpen Graph is a metadata vocabulary that controls how a URL appears when shared, defining the card title, description, image, and type.
PBKDF2PBKDF2 derives a cryptographic key from a password by applying a hash function many times with a salt, slowing brute-force attempts.
PDFPDF is a fixed-layout document format that packages text, fonts, images, and metadata so a file renders identically across devices.
Percent-encodingPercent-encoding replaces reserved characters in a URL with a percent sign and two hexadecimal digits so they survive transport as data.
Pomodoro techniqueThe Pomodoro technique structures work into fixed focus intervals separated by short breaks, traditionally twenty-five minutes of work and five of rest.
QR codeA QR code encodes text in a two-dimensional grid of modules with error correction, letting cameras recover the data even when part is damaged.
RegexA regular expression describes a text pattern for search, extraction, or light validation. Regex excels at flat strings and struggles with nested languages better handled by dedicated parsers.
robots.txtrobots.txt is a host-level file that tells crawlers which paths they may fetch; it controls crawling and not indexing.
SaltA salt is unique random data added to an input before hashing so identical values produce different digests and precomputed tables become useless.
Standard deviationStandard deviation summarises how far values typically sit from the mean, expressed in the same units as the underlying data.
SVGSVG is an XML-based vector image format that scales to any size without loss and can be styled or animated with CSS.
TimezoneA timezone is a named region with rules that map an instant to local time, producing different UTC offsets across the year.
UnicodeUnicode is the standard that assigns a unique code point to every character across writing systems, independent of how those points are encoded as bytes.
URL slugA slug is the human-readable portion of a URL path, normalised to lowercase words separated by hyphens with diacritics and punctuation removed.
UTF-8UTF-8 is a variable-length encoding of Unicode code points using one to four bytes, and it is byte-compatible with ASCII for the first 128 characters.
UUIDA UUID is a 128-bit identifier, often written as 36 hyphenated hex characters. Versions such as v4 (random) and v7 (time-ordered) optimize for different storage and privacy trade-offs.
VATVAT is a consumption tax added at each stage of supply, quoted either inclusive of tax as a gross price or exclusive of tax as a net price.
WCAGWCAG is the Web Content Accessibility Guidelines, a set of testable success criteria organised into A, AA, and AAA conformance levels.
Web Crypto APIThe Web Crypto API is the browser interface for hashing, HMAC, encryption, and cryptographically strong random values without external libraries.
WebPWebP is a modern image format supporting lossy and lossless compression plus transparency, typically 25–35% smaller than JPEG at similar quality.
XML sitemapAn XML sitemap lists the canonical URLs you want discovered, optionally with last-modified dates, to help crawlers find and prioritise pages.
YAMLYAML is an indentation-based data format designed for human-edited configuration, supporting comments and anchors that JSON lacks.