You don't want to change the way you work.
Subform introduces constraints into the visual design process, so it works a bit differently than traditional drawing tools. If you’re looking for a tool that works exactly like the one you currently use, you don’t have the time to learn new things, or you’re happy just throwing static images “over the wall” to developers—Subform’s probably not a fit.
You absolutely must have feature X.
We think it’s important for Subform to be useful as an expressive visual design tool. That said, we’re a tiny team and our priority isn't to clone every drawing tool already available. If there’s a feature or plugin you just can’t live without, Subform might not have it. (But do let us know what you're looking for.)
You can’t use an external vector drawing tool.
Speaking of features, Subform doesn’t currently support vector drawing (e.g. the pen tool, boolean operations). For now, we're focusing on dynamic layout of UIs—and letting tools like Adobe Illustrator handle illustration (specialized tools for specialized tasks). All is not lost: it’s easy to drag or paste SVGs right into Subform, preserving their vector data.
You need compatibility with an existing design tool.
We’re still focused on blazing a new path, so compatibility with other tools isn’t currently a priority. Since Subform’s layout engine is a different paradigm, it’s often better to just start fresh, anyway. If you can’t stomach rebuilding all the screens in your app in a new tool, you might want to wait until we’re further along.
You need integrated prototyping.
There’s no question prototyping is an important part of the product design process. But there are many different types of prototyping—and already so many prototyping tools in the market. At the moment, Subform's focus is on prototyping dynamic layout at design-time. More philosophically, our preference is to help get work into the actual production medium faster, rather than finessing high-fidelity simulacra that have to be entirely rebuilt during development.
You want a WYSIWYG static website editor.
Subform's target is designers and developers who are building and iterating on digital software products. If you’re looking for a visual design tool that can output HTML/CSS for a marketing site and publish it straight to the web, we recommend Webflow. They've built a great, mature product for this purpose.