# Cratis > Cratis is an open-source, MIT-licensed platform for building event-sourced and CQRS applications. At its center is Chronicle, an event-sourcing database and processing runtime with a first-class .NET SDK and additional TypeScript, Kotlin/Java (JVM), and Elixir clients, plus an experimental Go client — with a Python client coming soon — plus pluggable storage-provider implementations including MongoDB (default), PostgreSQL, SQL Server, and SQLite. ## About Cratis - Cratis is an open-source (MIT) event sourcing and CQRS platform for .NET, built around the Chronicle event-sourcing database. - Products: Chronicle (event store and runtime), Arc (CQRS framework with generated TypeScript proxies), Components (React UI library), Fundamentals, Specifications, CLI, Workbench, Chronicle MCP, and Cratis AI (rules and skills for AI agents). Screenplay, Stage, and Prologue are experimental; Studio is a paid product in Preview. - Licence: the open-source Cratis products are MIT licensed. Studio is paid. - Languages: Chronicle has a first-class .NET client and clients for TypeScript, Kotlin/Java, and Elixir, plus an experimental Go client; a Python client is coming soon and not yet published. Arc runs on ASP.NET Core and Spring Boot; Components targets React. - Storage: MongoDB (default), PostgreSQL, Microsoft SQL Server, or SQLite. - Downloads: over 2.5 million downloads across NuGet, npm, Docker Hub and Hex, counted October 2026. Chronicle, including its predecessors Aksio Cratis and the Dolittle Runtime: over 1.5 million downloads. Arc, including Aksio Cratis Applications and the Dolittle SDK: over 1.2 million downloads. - Get it from NuGet, npm, Maven Central, Hex, Docker Hub, and GitHub (https://github.com/Cratis). - Built by Cratis, a small company that builds and maintains the platform. - Capability map: https://www.cratis.io/cratis-stack/#capability-map. Support matrix: https://www.cratis.io/compatibility/#support-matrix. ## Key facts - Chronicle exposes a language-agnostic gRPC/protobuf boundary; its kernel runs on Microsoft Orleans. - Arc is an opinionated CQRS application framework — commands, queries, validation, authorization, and TypeScript proxy generation. It is implemented for ASP.NET Core and for Spring Boot on the JVM, and both generate against the same TypeScript packages. It works without event sourcing; Chronicle integration is optional. - Components is a React component library aligned with Arc patterns: command dialogs, typed forms, and query-backed data tables. - The CLI and Workbench are the inspection and diagnosis surfaces for Chronicle: events, observers, projections, read models, and failed partitions. - Screenplay is the declarative event-modeling language that Stage and Studio build on. ## Product documentation Choose a product and then a task area. The full-site downloads below are bulk archives, not the best default context for one question. - [Chronicle documentation](https://www.cratis.io/chronicle/llms.txt): Overview, guides and reference for Chronicle. - [Arc documentation](https://www.cratis.io/arc/llms.txt): Overview, guides and reference for Arc. - [Components documentation](https://www.cratis.io/components/llms.txt): Overview, guides and reference for Components. - [AuthProxy documentation](https://www.cratis.io/authproxy/llms.txt): Overview, guides and reference for AuthProxy. - [Screenplay documentation](https://www.cratis.io/screenplay/llms.txt): Overview, guides and reference for Screenplay. - [Prologue documentation](https://www.cratis.io/prologue/llms.txt): Overview, guides and reference for Prologue. - [CLI documentation](https://www.cratis.io/cli/llms.txt): Overview, guides and reference for CLI. - [Templates documentation](https://www.cratis.io/templates/llms.txt): Overview, guides and reference for Templates. - [Chronicle MCP documentation](https://www.cratis.io/chronicle-mcp/llms.txt): Overview, guides and reference for Chronicle MCP. - [Fundamentals documentation](https://www.cratis.io/fundamentals/llms.txt): Overview, guides and reference for Fundamentals. - [Fundamentals.Go documentation](https://www.cratis.io/fundamentals/go/llms.txt): Overview, guides and reference for Fundamentals.Go. - [Chronicle.Go documentation](https://www.cratis.io/chronicle/go/llms.txt): Overview, guides and reference for Chronicle.Go. - [Arc.Go documentation](https://www.cratis.io/arc/go/llms.txt): Overview, guides and reference for Arc.Go. - [Contributing documentation](https://www.cratis.io/contributing/llms.txt): Overview, guides and reference for Contributing. - [Architecture documentation](https://www.cratis.io/architecture/llms.txt): Overview, guides and reference for Architecture. - [Prompter documentation](https://www.cratis.io/prompter/llms.txt): Overview, guides and reference for Prompter. - [C# documentation](https://www.cratis.io/eventmodelers-ai/csharp/llms.txt): Overview, guides and reference for C#. - [Kotlin documentation](https://www.cratis.io/eventmodelers-ai/kotlin/llms.txt): Overview, guides and reference for Kotlin. - [Java documentation](https://www.cratis.io/eventmodelers-ai/java/llms.txt): Overview, guides and reference for Java. - [Chronicle full text](https://www.cratis.io/chronicle/llms-full.txt): Readable Markdown for Chronicle, with canonical page URLs. - [Arc full text](https://www.cratis.io/arc/llms-full.txt): Readable Markdown for Arc, with canonical page URLs. - [Components full text](https://www.cratis.io/components/llms-full.txt): Readable Markdown for Components, with canonical page URLs. - [AuthProxy full text](https://www.cratis.io/authproxy/llms-full.txt): Readable Markdown for AuthProxy, with canonical page URLs. - [Screenplay full text](https://www.cratis.io/screenplay/llms-full.txt): Readable Markdown for Screenplay, with canonical page URLs. - [Prologue full text](https://www.cratis.io/prologue/llms-full.txt): Readable Markdown for Prologue, with canonical page URLs. - [CLI full text](https://www.cratis.io/cli/llms-full.txt): Readable Markdown for CLI, with canonical page URLs. - [Templates full text](https://www.cratis.io/templates/llms-full.txt): Readable Markdown for Templates, with canonical page URLs. - [Chronicle MCP full text](https://www.cratis.io/chronicle-mcp/llms-full.txt): Readable Markdown for Chronicle MCP, with canonical page URLs. - [Fundamentals full text](https://www.cratis.io/fundamentals/llms-full.txt): Readable Markdown for Fundamentals, with canonical page URLs. - [Fundamentals.Go full text](https://www.cratis.io/fundamentals/go/llms-full.txt): Readable Markdown for Fundamentals.Go, with canonical page URLs. - [Chronicle.Go full text](https://www.cratis.io/chronicle/go/llms-full.txt): Readable Markdown for Chronicle.Go, with canonical page URLs. - [Arc.Go full text](https://www.cratis.io/arc/go/llms-full.txt): Readable Markdown for Arc.Go, with canonical page URLs. - [Contributing full text](https://www.cratis.io/contributing/llms-full.txt): Readable Markdown for Contributing, with canonical page URLs. - [Architecture full text](https://www.cratis.io/architecture/llms-full.txt): Readable Markdown for Architecture, with canonical page URLs. - [Prompter full text](https://www.cratis.io/prompter/llms-full.txt): Readable Markdown for Prompter, with canonical page URLs. - [C# full text](https://www.cratis.io/eventmodelers-ai/csharp/llms-full.txt): Readable Markdown for C#, with canonical page URLs. - [Kotlin full text](https://www.cratis.io/eventmodelers-ai/kotlin/llms-full.txt): Readable Markdown for Kotlin, with canonical page URLs. - [Java full text](https://www.cratis.io/eventmodelers-ai/java/llms-full.txt): Readable Markdown for Java, with canonical page URLs. ## Cross-product starting points - [Cratis stack](https://www.cratis.io/cratis-stack/) - [Build a full-stack feature](https://www.cratis.io/build-a-full-app/) - [Samples](https://www.cratis.io/samples/) ## Documentation Sets - [Abridged documentation](https://www.cratis.io/llms-small.txt): a compact version of the documentation for Cratis, with non-essential content removed - [Complete documentation](https://www.cratis.io/llms-full.txt): the full documentation for Cratis - [Chronicle first steps](https://www.cratis.io/_llms-txt/chronicle-first-steps.txt): For canonical page URLs and citations see https://www.cratis.io/chronicle/get-started/llms.txt - [Chronicle events](https://www.cratis.io/_llms-txt/chronicle-events.txt): For canonical page URLs and citations see https://www.cratis.io/chronicle/events/llms.txt - [Chronicle read models](https://www.cratis.io/_llms-txt/chronicle-read-models.txt): For canonical page URLs and citations see https://www.cratis.io/chronicle/read-models/llms.txt - [Arc first steps](https://www.cratis.io/_llms-txt/arc-first-steps.txt): For canonical page URLs and citations see https://www.cratis.io/arc/tutorial/llms.txt - [Components first steps](https://www.cratis.io/_llms-txt/components-first-steps.txt): For canonical page URLs and citations see https://www.cratis.io/components/tutorial/llms.txt ## Notes - The complete documentation includes all content from the official documentation - The content is automatically generated from the same source as the official documentation