Top Alternatives to Fluid UI

Lucidchart is a web-based application to draw diagrams.

OmniGraffle is a diagramming and digital illustration application for macOS and iOS.

ConceptDraw PRO is diagramming software used to create business graphics, including ConceptDraw Flowcharting Suite.

Apache OpenOffice Draw. Makes drawing business processes and diagrams a snap! Draw - from a quick sketch to a complex plan, Draw gives you the tools to communicate with graphics and diagrams. With a maximum page size of 300cm by 300cm, Draw is powerful tool for technical or general posters, etc.

Balsamiq Mockups is a rapid wireframing tool that helps you Work Faster & Smarter.

Moqups is a streamlined and intuitive web app that helps you create and collaborate on wireframes, mockups, diagrams and prototypes for any type of project.

Gliffy is software for diagramming via a HTML5 cloud-based app. It is used to create UML diagrams, floor plans, Venn diagrams, flowcharts and various other kinds of diagrams online.

Adobe XD is a commercial vector user experience design tool for designing web apps and mobile apps

InVision is a prototyping, collaboration & workflow platform.

Axure RP is a wireframing, rapid prototyping, documentation and specification software tool aimed at web and desktop applications.

Concept.ly is the Web and Mobile mockups tool. Convert wireframes and designs into interactive Apps.

SmartDraw is the smartest way to draw any type of chart, diagram: flowcharts, org charts, floor plans, network diagrams, and more.

Edraw Max is comprehensive mind mapping and planning tool network diagrams, floor plans, workflow diagrams, business charts, and engineering diagrams.

UXPin is a collaborative design platform, allowing entire teams to participate in the design process from start to finish.

Enterprise Architect is a visual modeling and design tool based on the OMG UML.

Mock up an application and show what's important, the idea, the information, the interaction.

Lovely Charts is an online diagramming application that allows you to create professional looking diagrams, such as flowcharts, sitemaps, organisation charts, etc.

Diagramo is an online flowchart software. It's FREE and Open Source ( GPL ) It's pure HTML5 Share and collaborate.

ProcessOn is an easy-to-use, free and powerful online diagram designer which support to share and real-time collaboration.

MockFlow is a collection of wireframe tools, prototyping tools, UI mockups, UX suite.

ProcessMaker is an Open source web-based workflow software and Business Process Management software.

Mockup Designer is an online mockup creator.