MDN Web Docs Glossary: Definitions of Web-related terms

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Falsy
A falsy value is a value that is considered false when encountered in a Boolean context.

Web technologies contain long lists of jargon and abbreviations that are used in documentation and coding. This glossary provides definitions of words and abbreviations you need to know to successfully understand and build for the web.

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Related Topics
  1. MDN Web Docs Glossary
    1. 404
    2. 502
    3. AJAX
    4. ALPN
    5. API
    6. ARIA
    7. ARPA
    8. ASCII
    9. ATAG
    10. Abstraction
    11. Accessibility
    12. Accessibility tree (AOM)
    13. Adobe Flash
    14. Algorithm
    15. Alignment container
    16. Alignment subject
    17. Alpha (alpha channel)
    18. Apple Safari
    19. Application Context
    20. Argument
    21. Arpanet
    22. Array
    23. Asynchronous
    24. Attribute
    25. Bandwidth
    26. Baseline
    27. BiDi
    28. BigInt
    29. Blink
    30. Block
    31. Block cipher mode of operation
    32. Boolean
    33. Boot2Gecko
    34. Bootstrap
    35. Bounding Box
    36. Breadcrumb
    37. Brotli
    38. Browser
    39. Browsing context
    40. Bézier curve
    41. CDN
    42. CIA
    43. CMS
    44. CORS
    45. CORS-safelisted request header
    46. CORS-safelisted response header
    47. CRLF
    48. CRUD
    49. CSP
    50. CSRF
    51. CSS
    52. CSS Object Model (CSSOM)
    53. CSS pixel
    54. CSS preprocessor
    55. Cache
    56. Cacheable
    57. CalDAV
    58. Call stack
    59. Callback function
    60. Canonical order
    61. Canvas
    62. Card sorting
    63. CardDAV
    64. Certificate authority
    65. Certified
    66. Challenge-response authentication
    67. Character
    68. Character encoding
    69. Character set
    70. Chrome
    71. Cipher
    72. Cipher suite
    73. Ciphertext
    74. Class
    75. Client hints
    76. Closure
    77. Code splitting
    78. Codec
    79. Compile
    80. Compile time
    81. Computer Programming
    82. Conditional
    83. Constant
    84. Constructor
    85. Continuous Media
    86. Control flow
    87. Cookie
    88. Copyleft
    89. Crawler
    90. Cross Axis
    91. Cross-site scripting
    92. Cryptanalysis
    93. Cryptographic hash function
    94. Cryptography
    95. DHTML
    96. DMZ
    97. DNS
    98. DOM (Document Object Model)
    99. DTLS (Datagram Transport Layer Security)
    100. DTMF (Dual-Tone Multi-Frequency signaling)
    101. Data structure
    102. Decryption
    103. Denial of Service
    104. Descriptor (CSS)
    105. Deserialization
    106. Developer Tools
    107. Digest
    108. Digital certificate
    109. Distributed Denial of Service
    110. DoS attack
    111. Doctype
    112. Document directive
    113. Domain
    114. Domain name
    115. Domain sharding
    116. Dominator
    117. Dynamic programming language
    118. Dynamic typing
    119. ECMA
    120. ECMAScript
    121. Effective connection type
    122. Element
    123. Empty element
    124. Encapsulation
    125. Encryption
    126. Endianness
    127. Engine
    128. Entity
    129. Entity header
    130. Event
    131. Exception
    132. Expando
    133. FTP
    134. FTU
    135. Fallback alignment
    136. Falsy
    137. Favicon
    138. Fetch directive
    139. Fetch metadata request header
    140. Firefox OS
    141. First CPU idle
    142. First Meaningful Paint
    143. First contentful paint
    144. First input delay
    145. First interactive
    146. First paint
    147. First-class Function
    148. Flex
    149. Flex Container
    150. Flex Item
    151. Flexbox
    152. Forbidden header name
    153. Forbidden response header name
    154. Fork
    155. Fragmentainer
    156. Function
    157. Fuzz testing
    158. GIF
    159. GIJ
    160. GPL
    161. GPU
    162. Gaia
    163. Garbage collection
    164. Gecko
    165. General header
    166. Git
    167. Global object
    168. Global scope
    169. Global variable
    170. Glyph
    171. Gonk
    172. Google Chrome
    173. Graceful degradation
    174. Grid
    175. Grid Areas
    176. Grid Axis
    177. Grid Cell
    178. Grid Column
    179. Grid Lines
    180. Grid Row
    181. Grid Tracks
    182. Grid container
    183. Guard
    184. Gutters
    185. Gzip compression
    186. HMAC
    187. HPKP
    188. HSTS
    189. HTML
    190. HTML5
    191. HTTP
    192. HTTP header
    193. HTTP/2
    194. HTTP/3
    195. HTTPS
    196. Hash
    197. Head
    198. High-level programming language
    199. Hoisting
    200. Host
    201. Hotlink
    202. Houdini
    203. Hyperlink
    204. Hypertext
    205. I18N
    206. IANA
    207. ICANN
    208. ICE
    209. IDE
    210. IDL
    211. IETF
    212. IIFE
    213. IMAP
    214. IP Address
    215. IPv4
    216. IPv6
    217. IRC
    218. ISO
    219. ISP
    220. ITU
    221. Idempotent
    222. Identifier
    223. Immutable
    224. Index
    225. IndexedDB
    226. Information architecture
    227. Inheritance
    228. Input method editor
    229. Instance
    230. Internationalization
    231. Internet
    232. Intrinsic Size
    233. JPEG
    234. JSON
    235. Jank
    236. Java
    237. JavaScript
    238. Key
    239. Keyword
    240. LGPL
    241. LTR (Left To Right)
    242. Latency
    243. Layout viewport
    244. Lazy load
    245. Ligature
    246. Local scope
    247. Local variable
    248. Locale
    249. Localization
    250. Long task
    251. Loop
    252. Lossless compression
    253. MIME type
    254. MVC
    255. Main Axis
    256. Main thread
    257. MathML
    258. Media
    259. Metadata
    260. Method
    261. Microsoft Edge
    262. Microsoft Internet Explorer
    263. Middleware
    264. MitM
    265. Mixin
    266. Mobile First
    267. Modem
    268. Modern web apps
    269. Modularity
    270. Mozilla Firefox
    271. Mutable
    272. NAT
    273. NNTP
    274. NaN
    275. Namespace
    276. Native
    277. Navigation directive
    278. Netscape Navigator
    279. Network throttling
    280. Node
    281. Node.js
    282. Normative
    283. Null
    284. Nullish value
    285. Number
    286. OOP
    287. OTA
    288. OWASP
    289. Object
    290. Object reference
    291. OpenGL
    292. OpenSSL
    293. Opera Browser
    294. Operand
    295. Operator
    296. Origin
    297. P2P
    298. PAC
    299. PDF
    300. PHP
    301. PNG
    302. POP3
    303. Packet
    304. Page load time
    305. Page prediction
    306. Parameter
    307. Parent object
    308. Parse
    309. Parser
    310. Perceived performance
    311. Percent-encoding
    312. Pixel
    313. Placeholder names
    314. Plaintext
    315. Polyfill
    316. Polymorphism
    317. Port
    318. Prefetch
    319. Preflight request
    320. Prerender
    321. Presto
    322. Primitive
    323. Privileged
    324. Progressive Enhancement
    325. Progressive web apps
    326. Promise
    327. Property
    328. Protocol
    329. Prototype
    330. Prototype-based programming
    331. Proxy server
    332. Pseudo-class
    333. Pseudo-element
    334. Pseudocode
    335. Public-key cryptography
    336. Python
    337. QUIC
    338. Quality values
    339. Quaternion
    340. RAIL
    341. RDF
    342. REST
    343. RGB
    344. RIL
    345. RSS
    346. RTCP (RTP Control Protocol)
    347. RTF
    348. RTL (Right to Left)
    349. RTP (Real-time Transport Protocol) and SRTP (Secure RTP)
    350. RTSP: Real-time streaming protocol
    351. Random Number Generator
    352. Raster image
    353. Real User Monitoring (RUM)
    354. Recursion
    355. Reference
    356. Reflow
    357. Regular expression
    358. Rendering engine
    359. Repo
    360. Reporting directive
    361. Request header
    362. Resource Timing
    363. Response header
    364. Responsive web design
    365. Robots.txt
    366. Round Trip Time (RTT)
    367. Routers
    368. Ruby
    369. SCM
    370. SCTP
    371. SDP
    372. SEO
    373. SGML
    374. SIMD
    375. SISD
    376. SLD
    377. SMPTE (Society of Motion Picture and Television Engineers)
    378. SMTP
    379. SOAP
    380. SPA
    381. SQL
    382. SQL Injection
    383. SRI
    384. STUN
    385. SVG
    386. SVN
    387. Safe
    388. Same-origin policy
    389. Scope
    390. Screen reader
    391. Script-supporting element
    392. Scroll container
    393. Scrollport
    394. Search engine
    395. Second-level Domain
    396. Secure Sockets Layer (SSL)
    397. Selector (CSS)
    398. Self-Executing Anonymous Function
    399. Semantics
    400. Serialization
    401. Server
    402. Server Timing
    403. Session Hijacking
    404. Shadow tree
    405. Shim
    406. Signature
    407. Simple header
    408. Simple response header
    409. Site
    410. Site map
    411. Sloppy mode
    412. Slug
    413. Smoke Test
    414. Snap positions
    415. Specification
    416. Speculative parsing
    417. Speed index
    418. Stacking context
    419. State machine
    420. Statement
    421. Static method
    422. Static typing
    423. Strict mode
    424. String
    425. Style origin
    426. Stylesheet
    427. Symbol
    428. Symmetric-key cryptography
    429. Synchronous
    430. Syntax
    431. Syntax error
    432. Synthetic monitoring
    433. TCP
    434. TCP handshake
    435. TCP slow start
    436. TLD
    437. TOFU
    438. TTL
    439. TURN
    440. Tag
    441. Telnet
    442. Texel
    443. Thread
    444. Three js
    445. Time to first byte
    446. Time to interactive
    447. Transmission Control Protocol (TCP)
    448. Transport Layer Security (TLS)
    449. Tratando Formulários com PHP
    450. Tree shaking
    451. Trident
    452. Truthy
    453. Type
    454. Type coercion
    455. Type conversion
    456. UDP (User Datagram Protocol)
    457. UI
    458. URI
    459. URL
    460. URN
    461. UTF-8
    462. UX
    463. Unicode
    464. Usenet
    465. User agent
    466. Validator
    467. Value
    468. Variable
    469. Vendor Prefix
    470. Viewport
    471. Visual Viewport
    472. VoIP
    473. W3C
    474. WAI
    475. WCAG
    476. WHATWG
    477. Web performance
    478. Web server
    479. Web standards
    480. WebDAV
    481. WebExtensions
    482. WebGL
    483. WebIDL
    484. WebKit
    485. WebM
    486. WebP
    487. WebRTC
    488. WebSockets
    489. WebVTT
    490. Whitespace
    491. World Wide Web
    492. Wrapper
    493. XForms
    494. XHR (XMLHttpRequest)
    495. XHTML
    496. XInclude
    497. XLink
    498. XML
    499. XPath
    500. XQuery
    501. XSLT
    502. beacon
    503. buffer
    504. caret
    505. document environment
    506. firewall
    507. frame rate (FPS)
    508. jQuery
    509. lossy compression
    510. markup
    511. mime
    512. minification
    513. non-normative
    514. privileged code
    515. undefined