Aspen
Aspen is a free API-testing app for macOS with an AI assistant, ideal for REST APIs.
At a glance
Starts at
Free
No paid plan found on the vendor's site, September 2026.
Free tier
Yes
Platforms
macOS
Best for
REST API developers and testers
Not for
Web api developers
3.9 out of 5
Scored by a Toolio reviewer after real useOur verdict
Aspen excels at testing REST APIs quickly. Great for teams needing local integration tools without login. Not suitable for complex security audits or heavy API integrations beyond basic tasks.
✓What it does well
Local TestingAPIs tested locally with no data saved externally.
AI AssistantAI helps generate code and OpenAPI specs for quick integrations.
Free ToolAbsolutely free to download and use immediately, no login required.
✕Where it falls short
Limited SecurityDoes not offer advanced security features or data encryption options.
No Web InterfaceOnly available as a macOS app, no web-based access.
Basic Collaboration ToolsCollections feature allows basic organization but lacks advanced collaboration tools.
Key features
REST API TestingOptimized for testing REST APIs quickly and efficiently.
AI IntegrationAI assistant speeds up integration processes with data generation and OpenAPI spec creation.
Local OperationsAll operations performed locally, ensuring no external data storage or handling.
Advanced Security FeaturesProvides limited security options without data encryption.