Developer & Web Tools Glossary
Plain-English definitions for the terms you encounter when working with online tools — Base64, JWT, DNS, regex, hash functions, and more. Each entry links directly to the relevant tool.
Developer Terms
What is Base64?
An encoding scheme that converts binary data into ASCII text. Used in email attachments, data URIs, and API payloads.
What is a JWT?
JSON Web Token — a compact, URL-safe token format for transmitting claims between parties. Used heavily in authentication.
What is JSON?
JavaScript Object Notation — a lightweight data-interchange format used by virtually every web API.
What is Regex?
A regular expression is a sequence of characters that defines a search pattern. Used to match, extract, and replace text.
What is a UUID?
Universally Unique Identifier — a 128-bit label used to uniquely identify objects in software systems.
What is a Unix Timestamp?
The number of seconds elapsed since 1 January 1970 (UTC). The universal way computers store and transmit time.
What is a Cron Expression?
A string of five or six fields that defines a schedule for automated tasks in Unix-based systems.
What is chmod?
A Unix command that sets file and directory permissions. The numeric codes (755, 644) define who can read, write, or execute.
What is URL Encoding?
A way to represent special characters in a URL using percent-encoded sequences like %20 for a space.
What is a URL Slug?
The human-readable part of a URL, typically derived from a page title. Uses hyphens and lowercase letters.
Security & Cryptography
What is a Hash Function?
A function that maps data of any size to a fixed-size output. Used for checksums, password storage, and data integrity.
What is MD5?
A widely-used hash algorithm that produces a 128-bit digest. Now considered cryptographically broken for security use.
What is SHA-256?
A member of the SHA-2 family producing a 256-bit hash. The current standard for secure hashing in most applications.
What is SSL/TLS?
Protocols that encrypt data in transit between a browser and a server. The padlock in your browser's address bar.
Network & Domain Terms
What is DNS?
The Domain Name System — the internet's phonebook, translating domain names like toolcrux.com into IP addresses.
What is WHOIS?
A protocol and database that stores registration information for domain names and IP addresses.
What are HTTP Headers?
Key-value pairs sent at the start of every HTTP request and response, carrying metadata about the content and connection.
What is an HTTP Redirect?
A server response that tells a browser to load a different URL. 301 is permanent, 302 is temporary.
What is a Subnet?
A logically separated segment of a network, defined by a subnet mask or CIDR notation like 192.168.1.0/24.
What is a QR Code?
A 2D barcode that encodes data — usually a URL — readable by smartphone cameras. QR stands for Quick Response.
Data Formats
What is CSV?
Comma-Separated Values — a plain-text format for tabular data. Each line is a row, each comma separates a column.
What is XML?
Extensible Markup Language — a flexible text format for structured data, similar to HTML but designed for data storage.
What is YAML?
A human-readable data serialisation format. Commonly used for config files in DevOps tools like Docker and Kubernetes.
What is Markdown?
A lightweight markup language using plain-text syntax to add formatting — headings, bold, lists — that renders to HTML.
Health & Calculators
About This Glossary
This glossary covers the terms you encounter most often when working with developer tools, web utilities, and network diagnostics. Every definition is written in plain English — no assumed background, no jargon left unexplained. Each entry links to a free tool on ToolCrux so you can go from understanding a concept to using it in seconds.
Terms are grouped by domain: developer concepts (Base64, JWT, regex, UUID), security and cryptography (hash functions, MD5, SHA-256, SSL/TLS), network and domain terms (DNS, WHOIS, HTTP headers), and data formats (JSON, CSV, XML, YAML, Markdown).