One declarative model
Classes, stored and calculated data, actions, constraints and forms are described in the same language. Changes in the model propagate through the application instead of being repeated across layers.
Code-first low-code platform for complex business applications
lsFusion reduces application boilerplate without hiding the code. Describe data, business rules and interfaces in one declarative language; let the platform handle persistence, queries, reactive updates and UI generation.
Low-code for developers, not a closed visual builder
The “low-code” part is the amount of infrastructure the platform derives from a compact model. The application itself remains explicit, versionable source code that a development team can review, test and extend.
Data processing without an ORM boundary
Set-oriented logic can be translated into optimized database queries. Developers work with business meaning while lsFusion decides how to execute operations on the application or database server.
Generated, reactive interfaces
Forms can combine editable and calculated data. The platform keeps values and interface state synchronized when data changes, reducing manual client-server plumbing.
A business model that becomes an application
This small lsFusion module declares a business object, two properties and a form. The same model can then grow with calculations, constraints, events, reports, security rules and integrations.
Explore more lsFusion examples or compare the platform’s full feature set.
CLASS Order 'Order';
isPosted 'Completed' = DATA BOOLEAN (Order);
number 'Number' = DATA INTEGER (Order);
FORM orders
OBJECTS o = Order
PROPERTIES(o) READONLY isPosted, number
;What open source means for your project
Open source is useful when it changes what your team can inspect, deploy and maintain—not merely when a repository is public.
- Platform and IDE source are available. Your developers can inspect platform behavior, propose changes and build a customized version when required.
- The platform is licensed under LGPL v3. It can be used, distributed and modified under the terms of a recognized free-software license.
- You choose the application environment. lsFusion applications can run on infrastructure you control, with direct access to operational diagnostics and the database.
- Extensions are not a dead end. Java interoperability, SQL access and integration mechanisms cover cases that should not be forced into a visual component model.
Where lsFusion fits best
The platform is aimed at transactional, data-intensive systems where business rules evolve and the cost of maintaining duplicated logic grows quickly.
ERP and operations
Orders, pricing, inventory, purchasing, finance, approvals and other connected processes with many calculations and constraints. See the dedicated ERP development platform overview.
Custom internal systems
Role-based workplaces, registries, workflows and back-office applications that must reflect a company’s own operating model.
Integration-heavy applications
Systems that combine a relational database with APIs, files, email, external services and existing Java or SQL components.
Is a code-first low-code platform right for you?
A strong fit when…
- business logic is more complex than a collection of CRUD screens;
- developers need source control, modularity and repeatable environments;
- the system processes large sets of related data and transactions;
- you want the productivity of low-code without giving up extensibility.
Probably not the first choice when…
- the goal is a marketing or content website;
- only non-technical users should build the application visually;
- the project is a disposable form or a very small standalone dashboard;
- a specialized off-the-shelf product already matches the process exactly.
Code-first low-code FAQ
Is lsFusion a no-code platform?
No. lsFusion is code-first low-code. Developers write a declarative model; the platform automates repetitive application infrastructure around it.
Is lsFusion really open source?
Yes. The platform and IDE source code are public, and the platform is distributed under the LGPL v3 license.
What applications is lsFusion designed for?
It is designed for data-intensive business applications with complex rules, transactions, forms, permissions and integrations—such as ERP, WMS and custom internal systems.
Can developers use Java or SQL?
Yes. Java interoperability, SQL access and integration mechanisms are available when a project needs application-specific extensions.
See the declarative approach in practice
Open the online environment, follow the examples, or review how lsFusion compares with conventional application development platforms.