The Wasm-based action builder is a new feature from Betty Blocks that brings the flexibility of high-code into the world of visual, low-code development. It lets developers write advanced logic in any language that compiles to WebAssembly (Wasm), such as Rust, C#, or Python, and then reuse that logic as drag-and-drop components within Betty Blocks.
This means teams no longer have to choose between full control (high-code) and speed (low-code). With the Wasm-based action builder, you get both.
High-code meets low-code
Traditionally, high-code and low-code have existed in separate silos. High-code offers total flexibility and control, but it comes with complexity and a reliance on scarce expert developers. Low-code is faster and more accessible, but often limited in how much it can be customized.
The Wasm-based action builder bridges this gap, allowing developers to:
- Write logic-heavy functions in their preferred programming language
- Compile them into Wasm
- Import them into Betty Blocks
- Let low-code builders configure and reuse them visually in workflows and applications
In other words, a high-code developer builds the core functionality once, and then low-code developers can use it many times without needing to touch the code.
Who is it for?
The Wasm-based action builder empowers two key personas in Betty Blocks:
- Low-code developers (the coders) – who work with APIs, set up remote models, and occasionally write code. They benefit from reusing Wasm logic without having to reimplement it
- Business technologists (the builders) – who configure apps visually. They can now use advanced logic components created by developers without needing to write a single line of code
Most low-code platforms come with limitations: you’re locked into their tech stack, their language, and their runtime. But with the Wasm builder, business logic is written in WebAssembly — a widely supported, open standard.
This means:
- You’re not tied to one language or one platform
- You can reuse logic elsewhere if needed
- Your team stays in control of your architecture
It’s a low-code platform that doesn’t force you into a proprietary box.
Wasm builder workflow
Using the Wasm-based action builder is straightforward. To get started, go to the Actions section and select Create new action > Wasm action. Give your action a name and description.
Add custom Wasm step
Inside the action builder, you’ll see any existing Wasm steps. To add a new one, click + Add custom Wasm step. In the form that appears, upload your .wasm file, then fill in the step’s name and description.
You can also customize the step by selecting an icon and color. A preview of the step will be shown at the bottom of the menu.
Create a new variable
Once created, your Wasm step will appear in the palette and can be dragged into the canvas. Just like other action steps, you can define variables, limited to three types: Text, Number, and Checkbox.
Wasm-based action builder menu
- Settings: Edit the action’s name and description, or delete the action entirely
- Download: Download the currently used .wasm file to your device
Practical use cases
1. Complex logic made modular and reusable
Companies often have custom logic, like pricing engines, rules, or legacy workflows, written in high-code. These are hard to understand or change unless you’re a specialist. With the Wasm-based action builder, this logic becomes a visual, reusable building block. It’s easier to document, configure, and scale.
2. Fast collaboration across teams
Instead of having a single developer bottlenecked with high-code tasks, the Wasm-based action builder allows teams to collaborate. High-coders write core functionality. Low-coders and business technologists use it in apps, pages, and workflows, speeding up delivery.
3. Gradually modernize legacy systems
Legacy systems often can’t keep up with modern needs. Rather than rebuild everything, teams can extract the valuable business logic, convert it to Wasm components, and reuse them in new apps.