Glossary
A developer glossary, written to teach — built to be cited.
1.4k terms across 32 categories — definitions, examples, common mistakes and fixes. Authored under one editorial standard. Cross-linked, searchable, and openly crawled by AI agents.
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Most referenced terms
Undefined Array Key / Offset Errors 3
Database Deadlocks 3
Exception Handling (try/catch/finally) 3
Accessible Forms 3
JavaScript Bundling — Vite, Webpack, esbuild 3
Observer Pattern 3
Path Traversal 3
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Last 7 days
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Image Optimisation
Reducing image file size and delivery overhead through format choice (AVIF, WebP), compression, responsive sizing (srcset), lazy loading, and explicit dimensions — the single highest-impact performance lever for most websites.
1mo ago
performance intermediate
Largest Contentful Paint (LCP)
A Core Web Vital that measures when the largest above-fold content element (typically the hero image or main heading) becomes visible — target under 2.5 seconds. The most impactful page speed metric.
1mo ago
performance intermediate
Mixed Content (HTTP on HTTPS)
When an HTTPS page loads resources (images, scripts, stylesheets) over HTTP — browsers block active mixed content and warn on passive, undermining the security of the HTTPS connection.
CWE-319
1mo ago
security intermediate
Open Graph Protocol
Meta tags that control how a page appears when shared on social platforms — title, description, image, and URL shown in link previews on Facebook, LinkedIn, Slack, Discord, and Twitter/X.
1mo ago
frontend beginner
Resource Hints (preconnect, prefetch, preload)
HTML link attributes that instruct the browser to take early action on resources — opening connections, fetching future pages, or loading critical assets before they are discovered in HTML parsing.
1mo ago
performance intermediate
Script Loading (defer, async, type=module)
How and when browser downloads and executes JavaScript — defer, async, and type=module control whether scripts block HTML parsing and in what order they run.
1mo ago
frontend intermediate
Structured Data — JSON-LD
Machine-readable schema markup embedded in a <script type='application/ld+json'> block, enabling Google rich results — star ratings, FAQs, breadcrumbs, events, and recipes in search.
1mo ago
frontend intermediate
API Versioning
Strategies for evolving an API without breaking existing consumers — URI versioning, header versioning, and content negotiation.
1mo ago
api_design intermediate
CSS Cascade Layers (@layer)
CSS @layer lets you explicitly define the order in which style groups are applied in the cascade — styles in a later layer always win over earlier ones regardless of specificity, eliminating specificity wars in large codebases.
1mo ago
frontend intermediate
Docker HEALTHCHECK
A Dockerfile instruction that defines how Docker tests whether a container is healthy — enabling automatic restart and load balancer removal on failure.
1mo ago
devops intermediate
Git Rebase vs Merge
Merge preserves branch history with a merge commit — rebase rewrites commits onto the target branch for a linear history.
1mo ago
git intermediate
HTTP Content Negotiation
The HTTP mechanism by which clients declare what formats, languages, and encodings they accept (Accept, Accept-Language, Accept-Encoding) and servers respond with the best match — or 406 Not Acceptable if none fits.
1mo ago
api_design intermediate
HTTP/2 Server Push & Early Hints
HTTP/2 Server Push lets a server proactively send assets (CSS, JS, fonts) before the browser requests them. 103 Early Hints is its practical successor — sending Link preload headers before the full response is ready.
1mo ago
networking intermediate
InnoDB vs MyISAM
InnoDB is the default MySQL storage engine supporting transactions, foreign keys, and row-level locking — MyISAM is legacy with table-level locking and no transaction support.
1mo ago
database beginner
INSERT ... ON DUPLICATE KEY UPDATE PHP 5.1+
An atomic MySQL upsert — inserts a new row or updates the existing one if a unique key constraint would be violated.
1mo ago
database intermediate
Linux File Permissions
Read, write, and execute permissions assigned to owner, group, and others — the foundation of Linux access control for web application files.
CWE-732 OWASP A5:2021
1mo ago
linux beginner
7.5
Memory-Mapped Files
A file mapped directly into a process's virtual address space — reads and writes go through the OS page cache rather than read()/write() syscalls, enabling fast access to large files and shared memory between processes.
1mo ago
linux advanced
Mutex vs Semaphore PHP 7.0+
A mutex allows only one thread to access a resource at a time — a semaphore controls access to a pool of N identical resources.
CWE-362
1mo ago
concurrency advanced
MySQL AUTO_INCREMENT
A column attribute that automatically assigns sequential integer IDs on INSERT — the standard primary key pattern in MySQL.
1mo ago
database beginner
MySQL charset=utf8mb4 PHP 5.1+
The correct MySQL character set for full Unicode support — including emoji and supplementary characters that the older utf8 charset cannot store.
1mo ago
php beginner