Messaging, explained

End-to-end encryptionA way of scrambling a message so that only the sender's device and the recipient's device can read it — the server carrying it cannot. Transport encryptionEncryption between your device and the server, and again between the server and the recipient — but not through the server itself. Pre-send screeningChecking a message against a policy before it is delivered, rather than after somebody reports it. Content moderationDeciding what a platform will and will not carry, and enforcing it. False positiveA message the screen refused that it should have allowed. AppealAsking a platform to reconsider a decision it made about you. MetadataEverything about a message except what it says: who sent it, to whom, when, how big it was, from where. Data retentionHow long a service keeps something after it stops needing it. Privacy policyThe document in which a service states what it collects, why, and who else sees it. Right to be forgottenThe ability to require a service to delete what it holds about you. Account deletionRemoving an account and the data attached to it, as opposed to disabling it. WebRTCThe browser technology that carries voice and video between people without a plugin or an app. STUN and TURNThe two servers that let a direct call find its way through home routers. VoIPVoice carried over the internet rather than a telephone network. LatencyThe delay between something being sent and it arriving. Edge computingRunning code in many small locations near users instead of one big data centre. CDNA network of servers that keep copies of a site's files close to the people asking for them. Core Web VitalsGoogle's three measurements of whether a page feels fast to the person using it. LighthouseGoogle's page-auditing tool, built into Chrome. AccessibilityMaking something usable by people with disabilities. Screen readerSoftware that reads a screen aloud for people who cannot see it. ARIAExtra attributes that tell assistive software what a piece of a page means. WCAGThe international standard for web accessibility. Reduced motionA system setting that asks software to stop moving things around. AnimationMotion used to explain a change rather than to decorate one. Dark modeA colour scheme with light text on a dark background, usually following a system setting. Progressive web appA website that can be installed like an app, with an icon, its own window and background notifications. Service workerA script a site installs in the browser that keeps running when the page is closed. Push notificationA message a server sends to a device that arrives even when the app or tab is closed. Notification permissionThe browser's one-time question about whether a site may interrupt you. No-install messagingMessaging that runs on a web page, with nothing to download. Managed deviceA phone or laptop an organisation controls, usually a school's or an employer's. FirewallA filter that decides which network traffic is allowed. School ChromebookA managed laptop issued by a school, usually locked down against installing software. Group chatA conversation with more than two people in it. Direct messageA private conversation between two people. ChannelA persistent space people join by link, rather than a conversation somebody adds them to. Invite linkA URL that grants entry to a space. Public channelA space anybody can find and join without being invited. Member directoryA searchable list of a platform's users. UsernameA short handle that identifies an account without revealing an email address or phone number. Phone number requirementA service insisting on a phone number to make an account. Email code sign-inSigning in with a code emailed to you instead of a password. PasskeyA credential stored on your device that signs you in without a password. PasswordA secret you type to prove who you are. Two-factor authenticationRequiring a second proof beyond a password. Read receiptA mark showing that a message has been opened. Typing indicatorA signal that the other person is composing a message. PresenceWhether somebody is currently available. MentionAddressing somebody by name inside a message so they are notified. ThreadA side conversation attached to one message. ReactionA small response attached to a message rather than sent as one. Message editingChanging a message after it has been sent. Message deletionRemoving a message after sending it. File sharingSending a document, image or video inside a conversation. Image screeningChecking a picture against a policy before it is delivered. MalwareSoftware written to harm the device it runs on. PhishingTricking somebody into handing over a credential. DoxxingPublishing somebody's private details in order to expose them to harm. HarassmentRepeated or targeted behaviour intended to distress somebody. BlockingStopping somebody from reaching you. Age verificationEstablishing how old somebody is. Age bandA coarse age range used to set protections without recording an exact age. Parental consentA parent's permission for a child's account. COPPAThe US law governing online services used by children under 13. FERPAThe US law protecting the privacy of student education records. GDPRThe EU's data protection regulation. CCPACalifornia's consumer privacy law. Global Privacy ControlA browser signal that tells sites not to sell or share your data. SEOMaking a page findable by search engines. Structured dataMachine-readable facts embedded in a page. Canonical URLThe address a page declares as its real one. Soft 404A page that says "not found" while returning a success status. Crawl budgetHow much of a site a search engine will fetch in a given period. SitemapA file listing a site's pages for search engines. robots.txtA file telling crawlers which parts of a site not to fetch. Generative engine optimizationWriting so that AI assistants quote you accurately. llms.txtA plain-text file describing a site for large language models. TLSThe protocol that puts the padlock in a browser's address bar, encrypting traffic between a device and a server. ServerlessRunning code without managing a server — the platform starts it on demand and bills for what it uses. CacheA stored copy of something, kept so it does not have to be fetched or computed again.