Kroki Pricing: Free Public Instance & Self-Hosted Options (2026)

Pricing overview

Kroki operates under a distinct pricing model that emphasizes accessibility and flexibility, primarily through a free public instance and an open-source self-hosting option. Unlike many commercial API services, Kroki does not offer tiered subscription plans or charge per API call. Its design is centered around providing a text-to-diagram rendering service without direct financial cost for its core functionality.

The core of Kroki's offering involves two main avenues for usage: a public online instance and a self-hostable server. The public instance is freely available for non-commercial applications, allowing users to generate diagrams by sending requests to a shared server. For commercial use cases, or those requiring specific performance, security, or data residency requirements, the recommended approach is to deploy a self-hosted Kroki server. This server software is open-source, meaning there are no licensing fees associated with its use, distribution, or modification. Costs for self-hosted deployments are limited to the underlying infrastructure (e.g., cloud computing, networking, storage) chosen by the implementer.

This model positions Kroki as a cost-effective solution, particularly for developers, technical writers, and teams who can either leverage the public instance or manage their own infrastructure. The absence of per-request charges or mandatory commercial tiers simplifies budget planning, as costs are predictable and directly tied to infrastructure provisioning rather than usage volume. For detailed setup instructions for a self-hosted server, refer to the Kroki installation documentation.

Plans and tiers

Kroki does not offer conventional commercial plans or tiered subscriptions. Instead, its operational model is structured around two fundamental usage options, each with distinct characteristics regarding cost, control, and suitability:

1. Public Online Instance: This is a shared service provided by the Kroki community. It is free to use and does not require registration or authentication. It is intended for non-commercial use cases, such as personal projects, educational purposes, or open-source documentation. Users send diagram definitions to a public endpoint, and Kroki renders the image. There are no associated direct costs from Kroki for using this instance.
2. Self-Hosted Server: Kroki provides its server software as open-source under the Apache License 2.0. This allows organizations and individuals to deploy the Kroki server on their own infrastructure, whether in a cloud environment, on-premises, or within a private network. This option provides complete control over data, performance, and security. The only costs incurred are those associated with the infrastructure itself, such as virtual machine instances, container services, network egress, and storage.

The following table summarizes the key distinctions between these two options:

Free tier and limits

Kroki's primary free offering is its public online instance. This instance functions as a free tier accessible to anyone without requiring an account or API key. The key limitation of this free tier is its restriction to non-commercial usage. While there are no explicitly stated rate limits or strict usage caps publicly documented for the free instance, users should operate under the assumption that excessive or abusive usage may be subject to throttling or temporary blocking to ensure fair access for all users.

For scenarios that fall outside of non-commercial use, or where dedicated resources and predictable performance are critical, the self-hosted solution serves as the de facto commercial alternative. Since the self-hosted server is open-source, it effectively extends Kroki's free usage model to commercial contexts, with the caveat that the user assumes responsibility for all operational and infrastructure costs. This model is common among open-source projects that provide a valuable service without direct monetization by the project maintainers, leaving commercial benefit to be derived from support, consulting, or integrated solutions.

Real-world cost examples

Estimating the real-world cost of using Kroki requires differentiating between the public instance and self-hosted deployments, as their cost structures are fundamentally different.

Public Online Instance

• Cost: $0.00
• Scenario: A developer uses Kroki's public instance to generate diagrams for their personal blog posts and open-source project documentation. They embed SVG diagrams rendered by Kroki directly into their GitHub README files and website.
• Explanation: As long as the use is non-commercial, the public instance incurs no direct cost. The developer benefits from a free service for generating diagrams without any infrastructure or maintenance overhead.

Self-Hosted Server on a Cloud Provider

For commercial or high-volume applications, self-hosting is the recommended and effectively free (software-wise) option. The costs are entirely dependent on the chosen infrastructure and usage patterns. Here are example scenarios using common cloud providers:

Example 1: Small-scale deployment on a Virtual Machine (VM)

• Provider: Google Cloud Platform (Compute Engine)
• Configuration: e2-small instance (2 vCPU, 2 GB RAM), 20 GB standard persistent disk, 100 GB network egress (for serving diagrams).
• Estimated Monthly Cost:
  • e2-small VM: ~$12 - $15 USD (region dependent)
  • Standard Persistent Disk: ~$0.80 USD
  • Network Egress: ~$12 USD (assuming $0.12/GB for 100GB)
  • Total Estimated Cost: ~$25 - $28 USD/month
• Use Case: An internal development team needs Kroki for generating diagrams in their Confluence documentation and CI/CD pipelines. They require data privacy and consistent performance for a few hundred requests per day.
• Considerations: Costs for load balancing, managed databases (if logs are stored externally), or more robust monitoring would add to this.

Example 2: Containerized deployment on a Managed Service

• Provider: AWS (ECS Fargate)
• Configuration: One Fargate task with 1 vCPU and 2 GB RAM, running 24/7. Load Balancer (ALB), minimal data transfer.
• Estimated Monthly Cost:
  • Fargate Task (1 vCPU, 2GB RAM): ~$40 - $50 USD (based on usage hours and region)
  • Application Load Balancer (ALB): ~$20 - $25 USD
  • Data Transfer: Negligible for internal use
  • Total Estimated Cost: ~$60 - $75 USD/month
• Use Case: A SaaS platform integrates Kroki to render user-generated diagrams within their application. They need high availability, scalability, and minimal operational overhead.
• Considerations: Fargate provides serverless container management, reducing operational burden. Costs scale with demand, so this estimate assumes a continuous running task. Auto-scaling configurations would lead to variable costs.

These examples illustrate that while Kroki itself is free software, the operational costs of a self-hosted instance are directly tied to the chosen infrastructure and the level of availability, performance, and scalability required.

How the pricing compares

Kroki's pricing model, characterized by a free public instance and open-source self-hosting, positions it distinctly against alternatives in the diagramming and visualization space. Most alternatives typically fall into one of three categories: fully free open-source tools, freemium models with paid advanced features, or subscription-based commercial services.

• Mermaid Live Editor (mermaid.live): Mermaid is an open-source JavaScript-based diagramming tool that renders diagrams from text. The Mermaid Live Editor is a free online tool to create and preview Mermaid diagrams, similar in concept to Kroki's public instance. Both are free for direct online use, but Mermaid's core library can also be embedded and used client-side or server-side without direct hosting costs for the rendering engine itself. Kroki, however, centralizes multiple diagramming engines, offering broader syntax support via a single API endpoint.
• PlantUML Online Server (plantuml.com/plantuml/uml): PlantUML is another text-to-diagram tool with an open-source core. Its online server provides a free public endpoint for rendering PlantUML diagrams, much like Kroki's public instance. The pricing comparison is largely identical: both offer free public services and open-source core software for self-hosting. Kroki differentiates by supporting PlantUML as one of its many backend engines, alongside others like Mermaid, Graphviz, Ditaa, and more, offering a unified interface for diverse diagram types.
• Excalidraw (excalidraw.com): Excalidraw is a virtual whiteboard for hand-drawn-like diagrams. It offers a free online version for collaborative diagramming and also provides an open-source library for self-hosting. Excalidraw's pricing model is similar to Kroki and PlantUML in its open-source nature. However, Excalidraw focuses on interactive, hand-drawn styles and real-time collaboration, contrasting with Kroki's focus on programmatic generation from text definitions. Excalidraw also has a commercial offering, Excalidraw+, which adds features like cloud storage, version history, and team management for a subscription fee, which Kroki does not directly offer.
• Commercial Diagramming Tools (e.g., Lucidchart, diagrams.net/draw.io): Many commercial diagramming solutions, like Lucidchart or even feature-rich versions of desktop applications, typically operate on a subscription model based on user count, features, storage, or API usage. While tools like diagrams.net (formerly draw.io) offer a robust free web application and integrate with various cloud storage providers, they do not provide a universal text-to-diagram API service like Kroki. For organizations seeking a programmatic approach to diagram generation without recurring subscription fees per user or API call, Kroki's self-hosting model presents a significantly lower total cost of ownership, as costs are limited to infrastructure and internal operational expenses.

In summary, Kroki stands out by offering a comprehensive set of diagramming engines through a unified API, without any direct licensing costs for its software. Its free public instance and open-source self-hosting options make it a highly cost-effective choice, especially when compared to commercial alternatives that charge for user licenses, advanced features, or API access. The primary cost consideration for Kroki users is the management and provisioning of their chosen infrastructure for self-hosted deployments.