API Arena
API Arena is a free competitive platform for students, self-taught backend developers, and teachers. You choose a challenge, build a real Spring Boot REST API, and upload the project as a ZIP. An isolated sandbox builds and runs that API, then real HTTP tests score it. It is measured practice, not a slide-only course.
Each submission is scored out of 1000. Up to 800 points come from technical HTTP tests against the running API: functional correctness (300), performance (300), and REST design (200). Up to 200 points come from an AI review. The default review rubric is heuristic, and a language-model provider can be enabled per environment. XP tracks cumulative progress. ELO is a separate competitive rating that moves against the score expected for your rating and the challenge difficulty. Submitting again below your best score on that challenge is penalized.
Create a free account and open the challenge catalog. Read the public preview, then sign in and start a timed session to see the full requirements. Zip a Maven project with pom.xml at the archive root and upload it. The pipeline builds the project in a sandbox, calls the API over HTTP, saves the score, and updates the leaderboard. The docs hub explains the first submission step by step.
A public challenge page is a preview only: title, description, difficulty, category, time limit, and XP reward. Endpoint lists, hidden tests, and hints are not on that page. They appear after you sign in and start a timed session. Getting Started. Español. llms.txt.