5 Best Open-Source & Free Diagram Tools for Businesses

Diagrams are a visually attractive and well-structured way of explaining complex ideas, concepts, data, processes, and relations between different elements. With the rise of free diagram tools and digital diagramming platforms, people quickly switched from paper drawings to 2D/3D digital diagrams.

This transition has made creating and editing diagrams a quick and simple affair. It has also made storing and sharing diagrams globally easy for all.

Building on the same, let’s discuss what diagramming software truly is. We will also look at some of the leading free online diagram tool options available in the market to help you choose the one that suits you best. The best part? Every tool on this list is free and open-source.

What is Diagramming Software?

Diagramming software is a program that allows users to visually represent information through diagrams and illustrations. It comes with built-in libraries of shapes, symbols, and tools that make it easy to create diagrams for different industries and use cases.

Using a diagramming tool, you can create mind maps, scientific illustrations, floor plans, project management diagrams, database diagrams, network diagrams, organizational charts, flowcharts, and more.

Many modern free diagram tools also include collaboration features, allowing multiple team members to work on the same diagram simultaneously, share feedback, and make changes in real time.

Common Types of Free Diagram Tools

Free diagram tools come in different types, each designed for a specific purpose and use case. Here are some of the most common ones…

Engineering diagram software: It is used to create precise technical drawings to convey information about the creation or functioning of an object. It is popular among engineers, contractors, electricians, and other related professionals.
UML diagram software: The software enables the creation of UML diagrams to visualize a system or project in terms of structure, behavior, and connectedness. It is mostly used by software engineers and teams looking for the best diagram tool for software architecture.
Flow diagram software: This flowchart software allows users to create sequenced diagrams that represent the outline, order, hierarchy, or workflow of an idea, process, or plan.
Business form software: This tool is used to create business forms such as memo forms, purchase order forms, invoice forms, bid proposal forms, job application forms, and more.
Business diagram software: It lets users create visual representations of business plans, processes, strategies, and solutions. Examples include SWOT diagrams, roadmaps, process maps, and organizational charts.
Fashion design software: This software helps users create designs, sketches, and concepts for accessories, jewelry, shoes, apparel, and more.
Infographics software: It is used to create visual representations of data for easier understanding and analysis. Examples include statistical, comparison, and how-to infographics.
Network diagram software: This software allows users to create simple or detailed network diagrams that show how different network components interact with each other.
Floor plan software: It helps create 2D and 3D building layouts and blueprints, making it easier to visualize and refine construction ideas before execution.
Wireframe design software: This software is mainly used by designers to create UI blueprints for websites and mobile applications.
Web diagram software: It helps users develop website maps, content structures, and other web-related diagrams.
Cards and presentation software: This diagramming tool enables users to create visual elements that can be used in presentations, reports, and cards.
Project management diagram software: It allows users to develop project plans with task dependencies, timelines, resource allocation details, and workflow structures.
Mind mapping software: Also known as concept mapping software, it enables users to visually organize ideas and depict relationships between them, making brainstorming easier.
Database diagram software: This software helps portray relationships between different database entities through entity-relationship diagrams.
Scientific illustration software: It allows users to create diagrams and illustrations that simplify complex scientific concepts and processes.
Organizational chart software: It enables the creation of an organization’s structural hierarchy and reporting relationships, helping employees understand the company’s structure more clearly.
Geo Maps software: It is used to represent locations on the Earth’s surface, making it easier to visualize geographic data and understand spatial relationships.

List of 5 Best Open-Source & Free Diagram Tools in 2026

With so many options available today, choosing the right free diagram tool can be difficult. To make the decision easier, we have rounded up 5 of the best open-source and free tools that can help you create everything from flowcharts and mind maps to software architecture and network diagrams. These include…

Tool	Best For	Why Choose It?
Diagrams.net (draw.io)	General diagramming, flowcharts, UML diagrams, and network diagrams	Completely free, open-source, and packed with templates for almost every diagramming need
Excalidraw	Brainstorming and sketch-style diagrams	Offers a simple hand-drawn look that’s perfect for quick idea visualization and collaboration
Mermaid.js	Developers and technical teams	Lets users create diagrams using text-based syntax, making documentation faster and easier
Lucidchart	Business workflows and team collaboration	Provides an intuitive interface with strong collaboration and diagramming capabilities
Miro	Remote teams and visual collaboration	Combines diagramming, brainstorming, and project planning in a collaborative online workspace

Now, let’s take a closer look at each one…

1. Diagrams.net (draw.io)

Diagrams.net (draw.io) is a popular free diagram tool used for creating flowcharts, UML diagrams, network diagrams, organizational charts, and more. It offers a simple drag-and-drop interface along with a large collection of templates and shapes, making it suitable for both beginners and experienced users.

The platform also supports cloud storage integrations, allowing users to save, share, and access diagrams easily across different devices.

Diagrams.Net

4.4

Starting Price

Price on Request

Key Features of Diagrams.net (draw.io):

Supports hundreds of diagram types, including flowcharts, UML diagrams, ER diagrams, network diagrams, BPMN workflows, org charts, and more
Provides extensive shape libraries for AWS, Azure, GCP, Cisco, software architecture, and business processes
Enables real-time collaboration with shared cursors and synchronized editing
Offers drag-and-drop diagram creation with automatic connectors and styling tools
Allows import and export across multiple diagram and document formats
Delivers offline desktop applications for Windows, macOS, and Linux
Supports cloud storage through Google Drive, OneDrive, Dropbox, GitHub, and GitLab
Integrates with Confluence, Jira, Notion, SharePoint, and Microsoft 365 environments
Preserves user control by storing diagram files in chosen storage locations rather than vendor-managed servers
Includes templates, themes, and customizable editor layouts for faster diagram creation

Diagrams.Net

4.4

Starting Price

Price on Request

Pro and cons of Diagrams.net:

Pros

Remains completely free and open source for individual users
Provides strong privacy since diagrams are not stored on draw.io servers
Supports both online and offline diagramming workflows
Offers broad integration options across productivity and development platforms
Delivers professional-grade diagramming without requiring an account
Enables easy file storage in existing cloud repositories
Maintains consistent functionality across browser, desktop, and integrated environments
Supports version-controlled workflows through GitHub and GitLab storage

Cons

Lacks some advanced enterprise collaboration capabilities available in premium diagramming platforms
Requires third-party storage services for cloud-based file management
Presents a learning curve for beginners due to the large feature set
Offers a more technical interface than some business-focused diagram tools

Diagrams.net (draw.io) Pricing & Plans: Diagrams.net is open-source and free online diagram tool.

Diagrams.net Supported Platforms: Supports web browsers, Windows, macOS, Linux, mobile devices, Google Drive, Google Workspace, OneDrive, SharePoint, Microsoft 365, Dropbox, GitHub, GitLab, Confluence, Jira, Notion, Nextcloud, and self-hosted Docker deployments.

2. Excalidraw

Excalidraw is a free online diagram tool known for its sketch-like, hand-drawn appearance. It is commonly used for brainstorming, planning, and visual discussions where a polished diagram is not necessary.

The platform focuses on simplicity, enabling users to quickly create diagrams, wireframes, and workflow sketches. Its real-time collaboration features also make it a popular choice for remote teams and group projects.

Excalidraw

Starting Price

$ 7.00

Key Features of Excalidraw:

Delivers a hand-drawn style canvas for diagrams, flowcharts, wireframes, and brainstorming sessions
Supports real-time collaboration with unlimited collaborators
Provides end-to-end encryption for enhanced privacy
Enables instant export to PNG, SVG, JSON, PDF, and PPTX formats
Offers cloud-based workspaces through Excalidraw+
Includes presentation mode for sharing ideas and walkthroughs
Supports voice hangouts and screen sharing for team discussions
Provides AI-powered text-to-diagram capabilities
Enables comments and feedback within shared workspaces
Integrates with Notion, Obsidian, and embeddable workflows

Excalidraw

Starting Price

$ 7.00

Pro and cons of Excalidraw:

Pros

Remains free and open source for core diagramming needs
Provides a simple interface with minimal learning curve
Supports instant collaboration without complicated setup
Offers an engaging sketch-style visual experience
Delivers strong privacy through encryption features
Enables quick diagram creation for technical and business teams
Supports self-hosting for organizations wanting greater control

Cons

Lacks advanced diagram libraries for UML, BPMN, ERD, and technical architecture mapping
Provides fewer built-in templates than many enterprise diagramming platforms
Focuses more on sketch-style whiteboarding than polished business diagrams
Offers limited formatting and design customization compared to tools like Lucidchart or Miro
Requires manual refinement for highly detailed professional documentation

Excalidraw Pricing & Plans: Excalidraw is a free and open-source diagramming tool.

Excalidraw Supported Platforms: Supports web browsers, self-hosted deployments, Notion, Obsidian, embedded web applications, and cloud-based collaborative workspaces.

3. Mermaid.js

Mermaid.js takes a different approach to diagramming by allowing users to create diagrams using text-based syntax. Instead of manually placing shapes on a canvas, users write simple code that is automatically converted into visual diagrams.

It supports flowcharts, sequence diagrams, Gantt charts, and more, making it especially useful for developers and technical writers. Many teams also consider it as the best diagram tool for software architecture documentation.

Key Features of Mermaid.js:

Supports text-based diagram creation using simple Markdown-like syntax
Provides flowcharts, sequence diagrams, ER diagrams, Gantt charts, mind maps, state diagrams, timelines, and more
Enables diagrams to be embedded directly within documentation and Markdown files
Integrates natively with developer tools and documentation platforms
Offers a free browser-based live editor for instant diagram generation
Allows version-controlled diagrams through text files stored in repositories
Supports self-hosting and embedding in custom applications
Includes AI-powered diagram generation through Mermaid Chart
Provides collaborative editing and commenting in Mermaid Chart
Enables drag-and-drop visual editing through Mermaid Chart

Pro and cons of Mermaid.js:

Pros

Remains completely free and open source at the core library level
Provides excellent integration with developer documentation workflows
Supports Git-friendly diagram management through plain text files
Offers a lightweight approach without complex drag-and-drop editing
Delivers fast diagram updates by simply editing text
Integrates seamlessly into existing developer ecosystems
Supports commercial use without licensing fees

Cons

Requires learning syntax instead of using visual drag-and-drop editing
Presents limitations when creating highly complex diagrams
Offers fewer visual customization options than dedicated diagram design platforms
Depends on Mermaid Chart for advanced collaboration capabilities

Mermaid.js Pricing & Plans: Mermaid.js is an open-source and free online diagram tool.

Mermaid.js Supported Platforms: Supports web browsers, GitHub, GitLab, Notion, Obsidian, Confluence, Jira, Google Docs, Microsoft Word, Microsoft PowerPoint, Visual Studio Code, JetBrains IDEs, self-hosted applications, and custom web applications.

4. Lucidchart

Lucidchart is a cloud-based diagramming platform designed for creating professional diagrams and visual workflows. It supports a wide range of diagram types, including flowcharts, process maps, network diagrams, and organizational charts.

The platform is known for its user-friendly interface and collaboration features, allowing multiple users to work on the same diagram simultaneously. It is widely used as flowchart software for planning, documentation, and process visualization.

Lucidchart

4.4

Starting Price

$ 9.00

Key Features of Lucidchart:

Enables creation of flowcharts, UML diagrams, ER diagrams, org charts, wireframes, and network diagrams
Supports real-time collaboration across teams and departments
Provides intelligent diagramming with data linking capabilities
Offers extensive templates and shape libraries for multiple use cases
Includes Visio import and export functionality
Enables revision history and version control for diagrams
Supports password-protected sharing and publishing
Provides AI-powered diagram assistance through Lucid AI
Integrates with workplace, productivity, and project management platforms
Includes enterprise-grade security, administration, and governance controls

Pro and cons of Lucidchart:

Pros

Delivers an intuitive drag-and-drop interface for fast diagram creation
Provides strong collaboration capabilities for distributed teams
Supports professional-grade diagramming across business and technical use cases
Offers extensive integration options for workplace productivity
Includes powerful version control and sharing controls
Enables import and export with Microsoft Visio
Provides scalable plans for individuals, teams, and enterprises

Cons

Limits the free plan to a small number of editable documents
Reserves enterprise security and governance features for higher-tier plans
Requires paid plans for advanced collaboration features and integrations

Lucidchart Pricing & Plans: It offers a free plan limited to 100 professional templates and 3 editable documents. For unlimited editable documents and the choice of more than a thousand professional templates, you can opt for a paid plan. Pricing starts at USD 9/month. You can also look into the best Lucidchart alternatives.

Lucidchart Supported Platforms: Supports web browsers, Windows, macOS, Microsoft 365, Microsoft Teams, Microsoft Visio, Google Workspace, Confluence, Jira, Slack, Salesforce, AWS, and enterprise SSO environments.

5. Miro

Miro is an online collaborative workspace that combines diagramming, brainstorming, and project planning in a single platform. Users can create flowcharts, mind maps, wireframes, and strategy boards while collaborating with team members in real time.

Unlike traditional diagramming platforms, Miro focuses heavily on teamwork and visual collaboration. Its flexible canvas and ready-made templates make it a popular free online diagram tool for remote and distributed teams.

Miro

4.4

Starting Price

$ 10.00

Key Features of Miro:

Enables collaborative whiteboarding for brainstorming, planning, workshops, and diagramming
Provides 7,000+ templates for business, design, agile, and technical workflows
Supports flowcharts, diagrams, Kanban boards, timelines, tables, slides, and docs on a single canvas
Offers real-time collaboration with comments, chat, screen sharing, and video calls
Includes AI-powered diagram generation, summaries, workflows, and content clustering
Provides advanced diagramming libraries including Mermaid, UML, BPMN, AWS, and cloud architecture shapes
Supports voting, timers, polls, and facilitation tools for workshops and meetings
Enables high-resolution exports, board backups, and version history
Integrates with hundreds of workplace and productivity applications
Includes enterprise governance, administration, and security controls

Pro and cons of Miro:

Pros

Delivers an intuitive drag-and-drop collaboration experience
Supports distributed and hybrid teams effectively
Provides extensive templates and ready-made frameworks
Offers strong facilitation tools for workshops and team sessions
Enables visual collaboration beyond traditional diagramming
Integrates with major business applications
Provides scalable plans for startups, consultants, and enterprises

Cons

Costs more than many dedicated diagramming tools
Limits the free plan to three editable boards
Requires higher-tier plans for advanced security and administration features
Presents a learning curve due to its broad functionality

Miro Pricing & Plans: Miro has a free plan with a limit of 3 editable boards. In addition, you can opt for the paid Starter, Business, or Enterprise option to get unlimited boards and collaboration tools. Annual pricing starts at USD 8/member/month.

Miro Supported Platforms: Supports web browsers, Windows, macOS, iOS, Android, Microsoft Teams, Microsoft 365, Jira, Confluence, Slack, Google Workspace, Azure DevOps, Asana, Adobe tools, Salesforce, AWS, and enterprise SSO environments.

Conclusion

A good diagram can turn a complicated idea into something anyone can understand. A good diagram tool can make the process just as simple.

So, experiment freely and find the platform that helps bring your ideas to life. If you need any help while doing so, Techjockey is just a call away.