eCommerce Engineering Glossary

Plain-English definitions of the terms you\'ll run into while working on Shopify, BigCommerce, Salesforce Commerce Cloud, NetSuite, and headless commerce projects. Written by engineers who actually ship on these platforms.

66 terms · last updated 2026-05-12

3PL (Third-Party Logistics): A logistics provider that handles warehousing, pick-pack, and shipping on behalf of a merchant. Common UK + EU 3PLs: ShipMonk, ShipBob, James and James, Huboo. Shopify and BigCommerce both integrate with most 3PLs via webhooks and the Fulfilment API.
Agentic Commerce Protocol (ACP): OpenAI-led specification for how AI agents complete a checkout on a participating merchant store. ACP is the buyer-agent contract; MCP and UCP are the storefront-side contracts that ACP-compliant agents call against.
AI Visibility: The measurable rate at which AI search engines (ChatGPT Search, Perplexity, Claude Web, Google AI Overviews, Bing Copilot) discover, parse, and cite a domain. Distinct from AI search ranking — visibility is upstream of ranking. Tracked via on-page audits plus prompt-level citation logging.
Answer Engine Optimization (AEO): The citation-winning subset of generative engine optimisation. Practices that make a page eligible to be the source ChatGPT, Perplexity, Claude Web, and Google AI Overviews actually quote — FAQPage schema, Speakable spec, citation-friendly first-60-word leads, llms.txt manifest specificity, and AI crawler allow-lists.
App Bridge: JavaScript SDK that lets Shopify embedded apps communicate with the Admin host frame — title bar, navigation, modals, toast messages, and resource pickers. Required for any Shopify app embedded inside the Admin.
BigCommerce Catalyst: BigCommerce's official Next.js + React Server Components headless storefront reference architecture. Successor to the legacy Cornerstone theme path for merchants who want headless without building from scratch.
BigCommerce Multi-Storefront: A BigCommerce account feature that lets merchants run multiple storefronts off a shared catalogue, with per-channel pricing, inventory, and checkout.
BigCommerce Stencil: BigCommerce's theme framework. Handlebars templates plus a component-based JavaScript layer, with SCSS styling and a CLI for local development.
Cart Transform Function: A Shopify Function that runs at cart-update time and can expand a line item into multiple bundle components or merge components into a parent bundle. Replaces the legacy Cart Transform App and powers Shopify Bundles.
Catalog MCP: The legacy Shopify MCP server (deprecated April 22, 2026) that exposed search_shop_catalog and lookup tools at /api/mcp. Replaced by the Universal Commerce Protocol with renamed tools: search_catalog, lookup_catalog, get_product.
Checkout Extensions: UI extensions to Shopify's hosted checkout that run in an isolated iframe with Shopify APIs. The current supported way to customise checkout after checkout.liquid deprecation.
Checkout MCP: Shopify MCP layer that handles the checkout primitive — create_checkout, update_checkout, complete_checkout — with a requires_escalation flag for human-in-the-loop steps that an agent cannot complete autonomously.
CLS (Cumulative Layout Shift): Sum of unexpected layout shifts during a page visit. Target: ≤ 0.1. Most commonly caused by images without explicit dimensions and fonts loaded without display: swap.
Composable Commerce: Extension of headless where multiple best-of-breed services (CMS, search, loyalty, etc.) are composed together with the commerce engine. Often uses MACH (Microservices, API-first, Cloud-native, Headless).
Content Security Policy (CSP): An HTTP response header that tells the browser which origins may load scripts, styles, images, frames, etc. Primary defence against Magecart-style XSS on eCommerce stores.
Core Web Vitals: Google's user-experience metrics used as ranking signals: Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS).
Custom Pixels: Shopify Plus-only feature for running custom analytics scripts in a sandboxed iframe at the checkout level. The supported path for non-standard tracking (server-side GTM, custom CDP integrations) after checkout.liquid deprecation.
Customer Account Extensions: UI extensions to the Shopify customer account section (order history, profile, subscriptions). The current supported way to customise the post-purchase customer experience.
Dev MCP: Shopify's developer-facing MCP server (shopify.dev MCP) that exposes documentation, API schemas, and code validation as tools for AI coding assistants. Used by Shopify Dev Assistant and the AI Toolkit skills.
Discount Function: A Shopify Function that returns programmatic discounts at cart time — automatic or code-based, line-item or order-level. Replaces the legacy Shopify Scripts discount path for new Plus merchants.
E-E-A-T: Experience, Expertise, Authoritativeness, and Trustworthiness — the quality framework Google raters (and ranking systems) use to evaluate content, particularly in YMYL topics.
Edge Rendering: Server-side rendering at a CDN's edge nodes rather than at a centralised origin. Common in Hydrogen (Oxygen), Next.js (Vercel Edge / Cloudflare), and BigCommerce Catalyst. Lowers TTFB and LCP by terminating rendering close to the user.
ERP: Enterprise Resource Planning — software that integrates core business processes (inventory, finance, procurement, HR). NetSuite, SAP, and Microsoft Dynamics are the dominant systems for mid-market and enterprise commerce.
European Accessibility Act (EAA): EU regulation requiring eCommerce sites selling to EU consumers to meet WCAG 2.1 AA accessibility standards. In force since 28 June 2025.
FAQPage Schema: A schema.org JSON-LD block listing Question + acceptedAnswer pairs on a page. Unlocks People Also Asked surface in Google and is heavily weighted by AI engines when selecting citation candidates for short-form answers.
flowTriggerReceive: Shopify Admin GraphQL mutation that lets external systems (AI agents, custom apps, integrations) start a Shopify Flow workflow by submitting a custom trigger handle and JSON payload. The opposite direction is `authenticate.flow()` which lets Flow call back into a custom app and verifies the request signature.
Generative Engine Optimization (GEO): Practices that improve a site's likelihood of being cited by generative AI search tools (ChatGPT, Claude, Perplexity). Overlaps with traditional SEO but emphasises structured content, clear answers, and machine-readable data.
Headless Commerce: Architecture where the storefront (frontend) is decoupled from the commerce platform (backend) and communicates via APIs. Enables custom UX at the cost of more engineering.
IndexNow: Protocol for instantly notifying search engines (Bing, Yandex, Seznam, Naver) that URLs have been added or updated. Host a key file at the domain root and POST JSON to api.indexnow.org.
INP (Interaction to Next Paint): The slowest interaction latency during a page visit. Replaced FID as a Core Web Vital in March 2024. Target: ≤ 200 ms.
ISR (Incremental Static Regeneration): Next.js rendering mode that pre-builds pages at build time and revalidates them in the background on a configured interval or on-demand. Common for product and category pages on Shopify Hydrogen and Next.js storefronts.
LCP (Largest Contentful Paint): Time from navigation start until the largest visible element finishes rendering. Target: ≤ 2.5 seconds at the 75th percentile of real users.
Liquid: Shopify's open-source templating language for themes and email templates. Uses {{ output }} and {% logic %} tags. Replaced for most checkout customisation by Checkout Extensions and for new merchants by Hydrogen on the storefront side, but still the foundation of Online Store 2.0 themes.
LLM Visibility: Citation rate and snippet quality across large-language-model answers — the share of relevant prompts where a domain appears in the generated response, and how prominent that citation is. The outcome layer on top of GEO/AEO inputs.
llms-full.txt: Companion to llms.txt — a single-file full-text dump of a site's content for retrieval-augmented generation. Engines that prefer bulk ingestion (some Perplexity and Claude Web crawlers) consume this format directly instead of crawling per-URL.
llms.txt: A plain-text file at the root of a site that summarises the site's purpose and structure for LLM crawlers. Proposed standard for AI-readable site navigation.
Metafield: Custom data attached to a Shopify resource (product, variant, customer, order, etc.). Typed (single line text, JSON, file reference, etc.) and queryable via the Storefront and Admin APIs. The basis for extending Shopify without a custom database.
Metaobject: Shopify's custom record type — a schema-defined entity (e.g. 'Brand', 'Recipe', 'Press Release') with typed fields, accessible across products, blogs, and themes. The successor to metafield-on-shop for structured site content.
Model Context Protocol (MCP): Open protocol from Anthropic that defines how AI agents discover and call external tools. In commerce, Storefront MCP exposes catalog search, checkout, and customer-account primitives to agents like ChatGPT and Perplexity. Each Shopify storefront ships a default MCP endpoint at /api/mcp.
NetSuite SuiteCommerce: Oracle NetSuite's commerce module. Tightly coupled to NetSuite ERP — orders, inventory, customers, and financials share a single data model with no integration middleware.
OCAPI: Open Commerce API — Salesforce Commerce Cloud's older REST API. Being replaced by the newer SCAPI for most use cases.
OMS (Order Management System): Software that orchestrates orders across multiple sales channels and fulfilment locations — routing, inventory allocation, returns, exchanges. Common Shopify OMS layers: Brightpearl, Cin7, Linnworks, Veeqo. ERPs (NetSuite, SAP) often include OMS modules.
PCI DSS: Payment Card Industry Data Security Standard. Required for any merchant handling card payments. Version 4.0 came into full effect in March 2025.
Polaris: Shopify's design system. Provides React component library, design tokens, and Polaris web components for building merchant-facing apps and admin extensions that match the native Shopify UI.
Salesforce Commerce Cloud (SFCC): Enterprise eCommerce platform from Salesforce. Runs on the SFRA reference architecture with custom cartridges, OCAPI, and SCAPI integrations.
SCAPI: Salesforce Commerce API — the newer, OpenAPI-described replacement for OCAPI with improved performance and consistency.
SFRA: Storefront Reference Architecture — the modern template and controller architecture for Salesforce Commerce Cloud storefronts, replacing the legacy SiteGenesis.
Shopify Admin API: GraphQL and REST API for managing merchants' back-office data — products, orders, customers, inventory, fulfilment. Used by apps and integrations.
Shopify AI Toolkit: Open-source set of Claude Code skills published by Shopify (github.com/Shopify/shopify-ai-toolkit, Apache 2.0, April 2026). Covers Admin GraphQL, Liquid, Hydrogen, Functions, Polaris extensions, and the use-shopify-cli execution skill that runs `shopify store execute` with the --allow-mutations gate.
Shopify Bundles: Shopify's native fixed-bundle and mix-and-match bundle product type. Implemented on top of the Cart Transform Function. Available without an app on every Shopify plan.
Shopify Flow: Shopify Plus's native workflow automation engine. Triggers on orders, customers, inventory, and products; supports conditions and multi-step actions.
Shopify Functions: Small WebAssembly modules that run inside Shopify's checkout, discount, cart-transform, delivery, and payment systems. Replace Shopify Scripts for new Plus merchants.
Shopify Hydrogen: Shopify's React-based framework for building custom storefronts on a headless Shopify backend. Built on Remix, deploys to Oxygen or Vercel.
Shopify Markets: Shopify's built-in internationalisation layer — multi-currency, translated storefronts, region-specific pricing and domain routing from a single store.
Shopify Oxygen: Shopify's managed edge hosting platform for Hydrogen storefronts. Co-located with Shopify infrastructure for lowest-latency Storefront API calls.
Shopify Plus: Shopify's enterprise tier. Adds checkout customisation (Scripts, Functions, Checkout Extensions), B2B features with company accounts and price lists, Shopify Markets multi-currency, Shopify Flow automation, higher API rate limits, and up to nine expansion stores.
Shopify Sidekick: Shopify's native AI assistant for merchants. Sits inside the Admin UI and authors Flow workflows, drafts product copy, and answers store-operations questions. Sidekick is a closed-loop assistant — distinct from the open Storefront MCP that exposes the store to external agents.
Shopify Storefront API: GraphQL API for reading products, collections, cart, and checkout data from Shopify. Used by headless storefronts including Hydrogen.
Speakable Schema: A schema.org SpeakableSpecification block that marks specific paragraphs or selectors as eligible for voice-extraction by Google Assistant and AI Overview voice readers. One of the strongest signals for AEO citation eligibility on long-form content.
Storefront MCP: The native MCP endpoint Shopify exposes on every storefront, covering catalog search, checkout, and customer-account primitives. Maps to the UCP endpoint at /api/ucp/mcp after the 22 April 2026 migration.
Structured Data (JSON-LD): Machine-readable metadata embedded in pages using schema.org vocabulary. Powers Google rich results and AI search engine citations.
SuiteScript: NetSuite's server-side scripting language (JavaScript variant) used to customise business logic, integrations, and UI behaviour across the platform.
SuiteTalk: NetSuite's SOAP and REST web services layer for external integrations. Used by most Shopify/BigCommerce ↔ NetSuite sync pipelines.
Theme App Extensions: Online Store 2.0 mechanism for apps to inject blocks into merchant themes without modifying theme code. Replaces the legacy Asset API approach. Merchant drags app blocks into the theme editor like any other section.
Universal Commerce Protocol (UCP): Joint Shopify + Google specification for agentic commerce. Layers a shopping service, capabilities, and extensions on top of MCP. Shopify migrated the Storefront Catalog MCP to UCP at /api/ucp/mcp on 22 April 2026, with hard sunset of the legacy /api/mcp endpoint on 15 June 2026.
Webhooks: HTTP callbacks fired by commerce platforms when events happen (orders/create, inventory/update, etc.). Essential for real-time sync between platforms.

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