> ## Documentation Index > Fetch the complete documentation index at: https://docs.pictify.io/llms.txt > Use this file to discover all available pages before exploring further. # Glossary > Key terms and definitions # Glossary A reference guide to terms used throughout the Pictify documentation. ## A ### API Key A secret token used to authenticate requests to the Pictify API. Comes in two types: live keys (`pk_live_`) for production and test keys (`pk_test_`) for development. ### Agent Screenshot An AI-powered feature that uses natural language prompts to navigate to a webpage and capture specific content automatically. ## B ### Batch Operation Processing multiple renders in a single API request. More efficient than individual requests for generating many images. ### Binding A connection between a template and an external data source that automatically refreshes the rendered image when data changes. ## C ### Canvas Rendering Generating images from FabricJS canvas JSON data, enabling programmatic image creation with objects, text, and shapes. ### CDN (Content Delivery Network) A globally distributed network that serves rendered images from locations close to users for faster loading. ## D ### Device Scale Factor A multiplier for output resolution. A factor of 2 produces "retina" images at 2x the specified dimensions. ## E ### Expression Dynamic code within templates using `{{...}}` syntax. Supports variables, operators, and built-in functions. ### Expression Engine The system that evaluates expressions in templates, providing features like string formatting, math operations, and conditionals. ## F ### FabricJS An open-source JavaScript canvas library. Pictify can render FabricJS canvas JSON directly to images. ## G ### GIF Capture Recording an animated GIF from a live webpage, capturing CSS animations or JavaScript-driven motion. ## H ### HMAC-SHA256 The cryptographic algorithm used to sign webhooks, ensuring they originate from Pictify and haven't been tampered with. ### HTML Rendering Converting HTML and CSS code into image formats like PNG, JPEG, or WebP. ## I ### Idempotency The ability to safely retry requests without duplicate effects. Enabled by the `Idempotency-Key` header. ### Idempotency Key A unique identifier included in requests to ensure they're only processed once, even if sent multiple times. ## M ### MCP (Model Context Protocol) A standard protocol for connecting AI models to external tools. Pictify's MCP server enables AI agents to generate images. ## O ### OG Image (Open Graph Image) The preview image shown when content is shared on social media platforms like Facebook, Twitter, and LinkedIn. ### OpenAPI A specification for documenting REST APIs. Pictify provides an OpenAPI 3.1 spec for API reference. ## P ### PDF Preset Standard paper sizes for PDF generation (A4, Letter, Legal, etc.) with predefined dimensions. ### Problem Details (RFC 9457) A standard format for API error responses that includes type, title, status, and detail fields. ## R ### Rate Limit Restrictions on how many API requests can be made in a time period. Varies by plan (Free: 60/min, Pro: 300/min, etc.). ### Render The process of converting templates, HTML, or URLs into images, GIFs, or PDFs. ### Retina Image A high-resolution image (typically 2x or 3x) optimized for high-DPI displays like Apple Retina screens. ### RFC 9457 The IETF standard for "Problem Details for HTTP APIs" used by Pictify's error responses. ## S ### Selector A CSS selector used to capture a specific element on a page rather than the full viewport. ### Signing Secret A cryptographic secret used to verify webhook signatures. Unique to each webhook subscription. ### SSRF (Server-Side Request Forgery) A security vulnerability where attackers trick servers into making unintended requests. Pictify blocks private network URLs to prevent SSRF. ## T ### Template A reusable design with variable placeholders that can be rendered with different data. ### Template Variable A placeholder in a template (like `{{title}}`) that gets replaced with actual data during rendering. ### Tool Schema JSON schema definitions for AI tool integration, describing available functions and their parameters. ### Transparent Background PNG or WebP images with alpha channel transparency instead of a solid background. ## U ### User Storage Optional cloud storage (S3, R2, etc.) where Pictify can upload rendered images in addition to the CDN. ## V ### Variable Interpolation The process of replacing template placeholders (`{{variable}}`) with actual values during rendering. ### Variable Set A collection of variable values used to render a template. Batch operations accept arrays of variable sets. ## W ### Webhook An HTTP callback that notifies your server when events occur (render completed, batch finished, etc.). ### Webhook Signature A cryptographic signature in the `X-Pictify-Signature` header used to verify webhook authenticity. ### WebP A modern image format developed by Google offering better compression than PNG or JPEG while supporting transparency. ## Common Abbreviations | Abbreviation | Full Term | | ------------ | -------------------------------------- | | API | Application Programming Interface | | CDN | Content Delivery Network | | CSS | Cascading Style Sheets | | DPI | Dots Per Inch | | GIF | Graphics Interchange Format | | HMAC | Hash-based Message Authentication Code | | HTML | HyperText Markup Language | | HTTP | HyperText Transfer Protocol | | JSON | JavaScript Object Notation | | JWT | JSON Web Token | | MCP | Model Context Protocol | | OG | Open Graph | | PDF | Portable Document Format | | PNG | Portable Network Graphics | | REST | Representational State Transfer | | SDK | Software Development Kit | | SSRF | Server-Side Request Forgery | | URL | Uniform Resource Locator | | UTC | Coordinated Universal Time |