API Tooling for the Modern Era
Design, Develop, and Use your APIs in an intuitive desktop application, while seamlessly maintaining an accurate OpenAPI-compliant specification.
NO proprietary collection formats, NO cloud sync, and NO messy sharing and permissions - use the collaboration methods your team is already comfortable with!
LEARN CALLOSUM IN A FEW SHORT VIDEOS
We have a YouTube playlist covering most of the features, from just getting started with an OpenAPI spec, all the way to the advanced features and topics. Subscribe to our channel for new feature updates!
GENERATE SPECS DIRECTLY FROM EXAMPLES
Getting started is the hardest part - not anymore! Effortlessly generate OpenAPI and schema specifications just by making requests. Callosum uses the request and response data structures to automatically generate comprehensive specs. Have a web app already? Record a HAR in your browser and generate the spec from a direct import!
AUTOMATE WORKFLOWS DIRECTLY IN-APP
In just a few clicks, automatically create variables from parsed response data, and use it in subsequent requests. No need for tedious scripting or un-intuitive configuration.
SCHEMA VALIDATION AND GENERATION
Code gets messy and APIs evolve quickly - Callosum validates every request and response against the JSON schemas, highlighting differences as they appear so that your team can identify changes before your customers do. A one-stop solution to simplify your API development and testing processes.
DOCUMENTATION
Integrated Markdown documentation for endpoints is directly editable in the GUI and saved to your OpenAPI spec, keeping your documentation cohesive and clear. Backend/Data Engineers and Frontend Developers can now use the same tool and have the same information easily accessible.
SECRET ENCRYPTION AND SHARING
Securely encrypt and share secrets within the spec document with Callosum, emphasizing that cloud sync is not necessary for sharing. We use standard AES-256-GCM symmetric encryption, so your own software can be easily updated to use the secrets directly without external dependencies.
OFFLINE FIRST
(Wait this is an API tool...) No really, you can work completely locally or on a restricted network, Callosum doesn't need access to the internet. Work securely and privately - 100% offline. Your data and API definitions stay on systems under your control. We don't force you to sync to our cloud, or share any more information than necessary. All of our features are included directly in the software on your computer.
LIGHTWEIGHT AND EFFICIENT
Callosum is not just powerful; it's also incredibly lightweight. Designed to be efficient, the desktop application works on macOS, Windows, and Linux, taking up less than 30 MB on disk and under 300 MB of memory in typical use. This efficiency means Callosum fits seamlessly into your development environment without getting in the way or slowing you down.