Developer Glossary

Base64 encodes binary data as 64 ASCII characters so it can travel safely in text formats like JSON or email. Decoding reverses the process to restore the original bytes.

JSON Web Token is a compact, URL-safe token with header, payload, and signature parts defined by RFC 7519. Servers use it to verify identity and claims without a session store.

JavaScript Object Notation is a lightweight, text-based data format for exchange defined by RFC 8259. It uses objects and arrays with strict syntax for interoperability.

A hash maps input of any size to a fixed-length digest that acts as a fingerprint. Cryptographic hashes like SHA-256 are one-way, deterministic, and sensitive to any tweak.

Cron is a time-based scheduler on Unix-like systems that runs commands from a five-field expression for minute, hour, day, month, and weekday. It automates recurring jobs reliably.

Universally Unique Identifier is a 128-bit value formatted as 36 hex characters used to identify resources without central coordination. Version 4 uses randomness for uniqueness.

Domain Name System translates human-readable domain names into IP addresses through a hierarchical, distributed database. It is the phone book that makes the web browsable.

Internet Protocol defines how packets are addressed and routed across networks using IPv4 or IPv6 addresses. Every device needs an IP to send and receive data on the internet.

URL encoding, or percent-encoding, replaces unsafe characters in URLs with % plus two hex digits per RFC 3986. It ensures links and query strings transmit correctly.

Markdown is a lightweight markup language that uses plain-text symbols to define headings, lists, and emphasis. It converts cleanly to HTML and is popular for docs and READMEs.

Portable Document Format preserves layout, fonts, and graphics consistently across devices per ISO 32000. It is ideal for sharing documents that look identical everywhere.

Image compression reduces file size by removing redundant or imperceptible data. Lossless keeps every pixel; lossy trades detail for much smaller files.

WebP is a modern image format from Google offering both lossy and lossless compression with smaller files than JPEG or PNG. It supports transparency and animation in one format.

Portable Network Graphics is a lossless raster format that preserves sharp edges and supports transparency. It is ideal for icons, screenshots, and graphics needing crisp detail.

JPEG is a lossy raster format optimized for photographs using discrete cosine transform compression. Adjustable quality lets you balance fidelity against file size efficiently.

Scalable Vector Graphics is an XML-based vector format that describes shapes with mathematical paths. It scales without pixelation and can be styled or scripted with CSS and JS.

Exchangeable Image File Format stores metadata inside JPEG and TIFF images, like camera settings, GPS, and timestamps. Tools can read or strip EXIF to protect privacy.

A MIME type, like text/html or image/png, tells browsers and servers what kind of content is being transmitted. Defined by IANA, it determines how the file should be handled.

Hypertext Transfer Protocol is the request-response protocol of the web defined by RFC 9110. A client sends a method and headers, and the server returns a status and body.

HTTPS is HTTP over TLS, encrypting requests and responses to provide confidentiality, integrity, and authentication. Browsers show a lock icon when the TLS certificate is valid.

Cross-Origin Resource Sharing is a browser security mechanism that controls cross-origin requests via HTTP headers. Servers must explicitly allow origins, methods, and headers.

Application Programming Interface is a contract that defines how software components interact through endpoints, parameters, and data formats. It enables reuse and integration.

Representational State Transfer is an architectural style for APIs using stateless HTTP methods and resource URLs. RESTful services use standard verbs and status codes predictably.

WebSocket is a protocol that upgrades an HTTP connection to a persistent, bidirectional channel per RFC 6455. It enables real-time messaging without repeated polling overhead.

Transmission Control Protocol provides reliable, ordered, error-checked delivery of byte streams over IP. It handles handshakes, retransmission, and flow control for web traffic.

User Datagram Protocol sends datagrams without guaranteed delivery, ordering, or connection setup. Its low overhead makes it ideal for DNS, video, and real-time applications.

Secure Sockets Layer, now succeeded by TLS, encrypts network traffic and authenticates servers via certificates. The term SSL is still used colloquially to mean TLS encryption.

Advanced Encryption Standard is a symmetric block cipher using 128, 192, or 256-bit keys approved by NIST. It encrypts data fast and securely in software and hardware worldwide.

RSA is an asymmetric cryptosystem using a public key for encryption and a private key for decryption. Its security relies on the difficulty of factoring large prime products.

Hash-based Message Authentication Code combines a secret key with a hash function to verify both integrity and authenticity. It is widely used to sign API requests securely.

Bcrypt is a password-hashing function that incorporates a salt and adaptive cost factor to resist brute-force attacks. It is the recommended choice for storing passwords safely.

Quick Response code is a two-dimensional barcode that stores data in a grid of black and white modules. Phones scan it to open URLs, connect to Wi-Fi, or share contact details.

A barcode encodes data as bars or patterns that scanners read optically. Linear formats like Code128 and EAN are used for product labeling and inventory tracking.

Regular expression is a pattern language for matching, searching, and manipulating text via concise syntax. It powers validation, parsing, and find-replace across many tools.

Diff compares two texts and highlights additions, deletions, and changes line by line. It underpins version control and helps reviewers spot what changed between versions.

YAML Ain't Markup Language is a human-readable data serialization format using indentation to denote structure. It is widely used for configuration files in DevOps workflows.

Extensible Markup Language is a strict, tag-based format for storing and transporting structured data defined by W3C. It supports schemas and namespaces for rigorous validation.

Tom's Obvious Minimal Language is a configuration format designed to be unambiguous and map cleanly to hash tables. Cargo and many Rust tools use TOML for settings.

Comma-Separated Values is a tabular text format where each line is a row and commas separate columns. It is the simplest way to exchange spreadsheet and database data.

Transport Layer Security encrypts data in transit and authenticates the peer via certificates, succeeding SSL. It secures HTTPS, email, and other protocols end-to-end.