The terms, in plain language.
Short definitions for the concepts behind the tools. Follow a link to put a definition to work.
Aspect ratio
Width divided by height: a description of shape, independent of pixel count. Try the related tool →
Base64
An encoding that represents bytes with a limited text alphabet. It is reversible and does not encrypt data. Try the related tool →
CSV
Delimited text records. Fields containing delimiters, quotes or line breaks require quoting rules. Try the related tool →
Checksum
A digest calculated from data bytes. Compare it with a trusted reference to check integrity. Try the related tool →
Contrast ratio
A comparison of the relative luminance of two colors. WCAG text thresholds depend on size and conformance level. Try the related tool →
JSON
A structured text format with objects, arrays, strings, numbers, booleans and null. Try the related tool →
Local storage
Browser storage associated with a site and browser profile. It is not a cross-device backup. Try the related tool →
Markdown
A plain-text writing syntax interpreted by a renderer. Implementations support different dialects. Try the related tool →
Percentage change
A directional comparison with a baseline: (new − old) ÷ old × 100. Try the related tool →
Percentage point
The arithmetic difference between two percentages. Moving from 20% to 25% is five percentage points. Try the related tool →
PPI
Pixels per inch: the density of image samples across a printed dimension. Printer dots per inch is a separate measure. Try the related tool →
PWA
A web application with installation and other app-like capabilities. Availability depends on the browser and device. Try the related tool →
Service worker
A browser-managed script that can handle requests, offline caches and push events within its scope. Try the related tool →
URL encoding
A percent-encoded representation of bytes used to safely represent a URL component. Try the related tool →
UTF-8
A variable-length encoding of Unicode code points as bytes. Non-ASCII characters often require multiple bytes. Try the related tool →
UUID v4
A 128-bit identifier with 122 random bits and fixed version and variant bits. Try the related tool →
Unix timestamp
A count from the Unix epoch. Seconds and milliseconds are different units and must be explicit. Try the related tool →
Watt-hour
Energy: one watt sustained for one hour. Different from watts, which describe power at a moment. Try the related tool →