Top 10 Open Source Alternatives to Fluid UI in 2025: A Comprehensive Guide

Fluid UI has long been a popular choice for wireframing and prototyping, but the open-source community offers several compelling alternatives. Here, we explore the top 10 open-source alternatives to Fluid UI in 2025, highlighting their key features, ease of use, and unique benefits.

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1. Penpot

Description: Penpot is an open-source, web-based design and prototyping platform that emphasizes collaboration across the entire product team. It is designed to be cross-platform and accessible via a browser.
Key Features:
Real-time collaborative editing, allowing multiple users to work on the same design simultaneously.
A wide array of design tools for creating pixel-perfect UIs and interactive prototypes.
Ability to host the application on your own server, offering more control over data and security.
Built-in commenting and feedback mechanisms to streamline the review process.
Designed to be interoperable with other design tools by supporting standard file formats.
Learn more about Penpot

2. Pencil Project

Description: Pencil Project is a free, open-source GUI tool for creating wireframes, mockups, and prototypes. It's available as a downloadable application for Windows, Mac, and Linux, and also as a Firefox add-on.
Key Features:
Extensive library of built-in templates and stencils for various UI elements.
Diagramming capabilities that are useful for illustrating wireflows and user journeys.
Connector tools for quickly linking elements and pages.
Available as a downloadable application for offline use, which can be beneficial for designers working in environments with limited internet.
Completely free.
Explore Pencil Project

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3. Draw.io

Description: draw.io is an open-source, browser-based diagramming application that can be used to create various types of visuals, including flowcharts and UI diagrams.
Key Features:
A wide range of templates for different diagram types, including flowcharts, wireframes, and network diagrams.
Easy to use drag and drop interface.
Integrations with various cloud storage platforms such as Google Drive, OneDrive, and Dropbox.
It is a free, open-source, and browser-based application.
Files can be shared with others in many formats including .pdf and .svg.
Learn more about Draw.io

4. Figma

Description: While Figma isn't exclusively open-source, it offers a very robust free plan and is widely used for UI design, wireframing, and prototyping. It's a cloud-based platform that excels in team collaboration.
Key Features:
Real-time collaboration, allowing multiple designers and stakeholders to work concurrently on a project.
Wide range of tools for design and prototyping, from low to high fidelity.
Supports animations, hover effects, and other interactions, which is great for prototyping user experience.
Very large selection of plugins to extend its functionality.
Free starter plan for up to two editors and three projects.
Explore Figma

5. Miro

Description: Miro is an online collaborative whiteboarding platform that is great for visual collaboration, including wireframing and design.
Key Features:
It offers a large, infinite canvas to visualize ideas.
Real-time collaboration for teams to work together.
Many built-in templates and pre-made design components to help create quick prototypes and wireframes.
Supports various forms of media such as images, videos, and documents.
Free plan available for new teams.
Learn more about Miro

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6. Wireframe.cc

Description: Wireframe.cc is a minimalist, browser-based wireframing tool that emphasizes simplicity and ease of use.
Key Features:
Clean, distraction-free interface to focus on core wireframing tasks.
Browser-based, which means no installation is needed and it works on any operating system.
Very simple, intuitive design.
Basic elements for rapid wireframing.
Free to use with a basic feature set.
Discover Wireframe.cc

7. MockFlow

Description: Mockflow is an online wireframe tool that facilitates collaborative UI design.
Key Features:
Provides a user-friendly interface for creating wireframes.
Offers a library of UI components.
Collaboration tools for teams to work together on designs.
Free plans and flexible pricing options.
Tools for both low and high fidelity design.
Explore Mockflow

8. UXPin

Description: UXPin is an end-to-end platform for UI/UX design with tools for creating interactive and high fidelity prototypes.
Key Features:
Thousands of pre-built design components to create comprehensive design systems.
User-friendly with an easy to navigate interface.
Low code interface for building interactive prototypes.
Ideal for both beginner and pro designers.
Collaboration tools for teams to work together.
Learn more about UXPin

9. Locofy

Description: Locofy is a tool that helps bridge the gap between designers and developers, by converting Figma designs into developer-ready code.
Key Features:
Seamless conversion process from design to code.
Supports various coding frameworks.
Tools to work directly with the code generated.
Allows designers and developers to collaborate more effectively.
Designed to significantly reduce the time it takes to convert designs to code.
Discover Locofy

10. ToolJet

Description: ToolJet is an open-source, low-code platform for building internal tools.
Key Features:
Drag and drop UI builder for quick UI creation.
Integration with external APIs.
Role-based access control for user management.
Open source, so it is customizable and extensible.
Can be used to build a wide variety of internal tools.
Explore ToolJet

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FAQ

1. What is Penpot used for?

Penpot is an open-source, web-based design and prototyping platform, emphasizing collaboration across entire product teams. It supports real-time collaborative editing, and it can be hosted on your own server for enhanced control over data and security. Learn more about Penpot

2. What are the main features of Pencil Project?

Pencil Project is a free, open-source GUI tool designed for wireframes, mockups, and prototypes with built-in templates and stencils, diagramming capabilities, and offline functionality as a downloadable application. Discover Pencil Project

3. Can I use Draw.io with cloud storage platforms?

Yes, Draw.io integrates with various cloud storage platforms such as Google Drive, OneDrive, and Dropbox. It also offers templates for flowcharts, wireframes, and network diagrams with a drag-and-drop interface. Learn more about Draw.io

4. What makes Figma suitable for team collaboration?

Figma excels in team collaboration by supporting real-time collaboration, a wide range of design and prototyping tools, interaction effects for prototyping user experiences, and an extensive selection of plugins. Explore Figma

5. How can Miro be used in design?

Miro provides a large, infinite canvas for visualizing ideas and supports real-time team collaboration. It includes built-in templates, pre-made design components, and supports various forms of media. Discover Miro

6. What is the key benefit of Wireframe.cc?

Wireframe.cc is designed to be minimalist and browser-based, offering a clean interface for core wireframing tasks with basic elements for rapid wireframing. Learn more about Wireframe.cc

7. How does MockFlow aid in UI design?

MockFlow facilitates collaborative UI design with a user-friendly interface, a library of UI components, tools for both low and high fidelity design, and free plans for flexible pricing options. Learn more about MockFlow

8. What does UXPin offer for prototyping?

UXPin is an end-to-end platform with tools for creating interactive and high-fidelity prototypes, including thousands of pre-built design components, a user-friendly interface, and collaboration features. Discover UXPin

9. How does Locofy bridge the gap between designers and developers?

Locofy converts Figma designs into developer-ready code, supporting various coding frameworks and offering tools for direct code interaction, thus promoting effective collaboration between designers and developers. Learn more about Locofy

10. What is ToolJet used for?

ToolJet is an open-source, low-code platform for building internal tools with a drag-and-drop UI builder, integration with external APIs, role-based access control, and the ability to construct various internal applications. Explore ToolJet

About the Author

Violetta Bonenkamp, also known as MeanCEO, is an experienced startup founder with an impressive educational background including an MBA and four other higher education degrees. She has over 20 years of work experience across multiple countries, including 5 years as a solopreneur and serial entrepreneur. She’s been living, studying and working in many countries around the globe and her extensive multicultural experience has influenced her immensely.

Violetta is a true multiple specialist who has built expertise in Linguistics, Education, Business Management, Blockchain, Entrepreneurship, Intellectual Property, Game Design, AI, SEO, Digital Marketing, cyber security and zero code automations. Her extensive educational journey includes a Master of Arts in Linguistics and Education, an Advanced Master in Linguistics from Belgium (2006-2007), an MBA from Blekinge Institute of Technology in Sweden (2006-2008), and an Erasmus Mundus joint program European Master of Higher Education from universities in Norway, Finland, and Portugal (2009).

She is the founder of Fe/male Switch, a startup game that encourages women to enter STEM fields, and also leads CADChain, and multiple other projects like the Directory of 1,000 Startup Cities with a proprietary MeanCEO Index that ranks cities for female entrepreneurs. Violetta created the "gamepreneurship" methodology, which forms the scientific basis of her startup game. She also builds a lot of SEO tools for startups. Her achievements include being named one of the top 100 women in Europe by EU Startups in 2022 and being nominated for Impact Person of the year at the Dutch Blockchain Week. She is an author with Sifted and a speaker at different Universities. Recently she published a book on Startup Idea Validation the right way: from zero to first customers and beyond and launched a Directory of 1,500+ websites for startups to list themselves in order to gain traction and build backlinks.

For the past several years Violetta has been living between the Netherlands and Malta, while also regularly traveling to different destinations around the globe, usually due to her entrepreneurial activities. This has led her to start writing about different locations and amenities from the POV of an entrepreneur. Here’s her recent article about the best hotels in Italy to work from.

About the Publication

Fe/male Switch is an innovative startup platform designed to empower women entrepreneurs through an immersive, game-like experience. Founded in 2020 during the pandemic "without any funding and without any code," this non-profit initiative has evolved into a comprehensive educational tool for aspiring female entrepreneurs.The platform was co-founded by Violetta Shishkina-Bonenkamp, who serves as CEO and one of the lead authors of the Startup News branch.

Mission and Purpose

Fe/male Switch Foundation was created to address the gender gap in the tech and entrepreneurship space. The platform aims to skill-up future female tech leaders and empower them to create resilient and innovative tech startups through what they call "gamepreneurship". By putting players in a virtual startup village where they must survive and thrive, the startup game allows women to test their entrepreneurial abilities without financial risk.

Key Features

The platform offers a unique blend of news, resources,learning, networking, and practical application within a supportive, female-focused environment:

Skill Lab: Micro-modules covering essential startup skills
Virtual Startup Building: Create or join startups and tackle real-world challenges
AI Co-founder (PlayPal): Guides users through the startup process
SANDBOX: A testing environment for idea validation before launch
Wellness Integration: Virtual activities to balance work and self-care
Marketplace: Buy or sell expert sessions and tutorials

Impact and Growth

Since its inception, Fe/male Switch has shown impressive growth:

3,000+ female entrepreneurs in the community
100+ startup tools built
5,000+ pieces of articles and news written

Partnerships

Fe/male Switch has formed strategic partnerships to enhance its offerings. In January 2022, it teamed up with global website builder Tilda to provide free access to website building tools and mentorship services for Fe/male Switch participants.

Recognition

Fe/male Switch has received media attention for its innovative approach to closing the gender gap in tech entrepreneurship. The platform has been featured in various publications highlighting its unique "play to learn and earn" model.