CircleCI vs Travis CI

CircleCI's REST API triggers and inspects pipelines, workflows, and jobs, and manages projects, contexts, and self-hosted runners. The stored v1-reference docs URL now 404s live — CircleCI has fully moved API documentation to v2, whose own v1 docs page carries a banner recommending migration to v2 endpoints — so the URL was corrected to the current v2 reference. Authentication is reconfirmed as a personal API token: an unauthenticated GET to api/v2/me returned 401, and that same response (plus its OPTIONS preflight) carried no access-control-allow-origin header at all despite a Vary: Origin header, resolving CORS to closed rather than open. CircleCI's pricing page offers a Free plan (30,000 monthly credits, more for open source) alongside paid Performance plans, making it freemium.

Travis CI's REST API reads and manages builds, repositories, branches, and jobs, and its docs specify a token-based Authorization: token "<token>" header rather than an OAuth redirect flow, reconfirming the stored API Key auth model. A live GET against api.travis-ci.com returned a structured JSON response (not a raw connection error), and the same request sent with an Origin header carried access-control-allow-origin: * on both the GET and its OPTIONS preflight, resolving the previously unknown CORS support to open. Travis CI's own pricing page still lists an "Open Source Only" free tier alongside paid Linux/FreeBSD plans, so it remains freemium rather than fully paid.