Mockzilla

Overview

Mockzilla creates mock APIs from OpenAPI specifications or plain JSON, for frontend development, integration tests and demos. It is best suited to developers who want controllable responses locally or in CI, with hosted workflows as an option. Its strongest case is a broad simulation toolkit; the Free tier’s restricted access and short history window make it more of an evaluation path than a durable service.

Key features

OpenAPI imports can generate realistic schema-based responses and validate requests against the spec, helping teams catch contract mismatches while frontend work proceeds. Plain JSON offers a simpler starting point when no spec is available. Per-service or per-endpoint latency and error injection lets developers exercise retry and fallback behavior deliberately rather than waiting for failures to occur.

The proxy can send requests through to a real backend while mocking routes that backend does not serve. That makes it a useful fit for partially implemented APIs, though it is less compelling when a team needs only static fixtures. A GitHub Action creates a mock URL for each pull request, updates it on pushes and removes it when the branch is gone, which supports isolated review and CI environments. Request history records status and timing, with replay for individual requests or sets; the Free plan retains that history for only two hours.

Mockzilla also describes payment-provider simulations covering declines, 3D Secure flows, lifecycle operations and idempotency. The site lists a GitHub Action and an MCP server for coding agents, and its CLI instructions cover Claude and Gemini. The CLI is MIT-licensed, runs offline and can be used on a laptop or in CI; hosted cloud features are opt-in. HTTP is the supported protocol.

Privacy protections include TLS in transit, encryption at rest and simulations in isolated environments with scoped access. Those safeguards do not make Mockzilla suitable for sensitive uploads: its terms prohibit personally identifiable information, real financial data, health records, credentials and other sensitive content.

Pricing

The Free plan costs nothing and allows 1K requests/mo, 5 req/s, one simulation and 10 MB of data transfer. API access is unavailable, so the free allowance is most useful for evaluation rather than an ongoing API workflow.

Hobby costs $10/mo and raises the limits to 100K requests/mo, 10 req/s, two simulations and 1 GB of transfer, making it the entry paid option for side projects. Starter costs $20/mo for 200K requests/mo, 20 req/s, five simulations and 4 GB of transfer; it is aimed at solo developers and small teams. Pro costs $50/mo for 400K requests/mo, 40 req/s, ten simulations and 16 GB of transfer, a better match for teams running CI pipelines. Each step up increases capacity, but the published allowances still make traffic and simulation count important buying constraints.

Enterprise has custom pricing, dedicated infrastructure, an own domain and sizing to traffic, for organizations needing a deployment tailored to their workload. Verified students can apply for a free tier without a card; applications receive manual review, which usually takes 1–2 business days.

Platforms

Mockzilla supports API, Linux, macOS, Windows, web and self-hosted use. The offline CLI gives local and CI users a route that does not depend on hosted cloud features, while hosted workflows remain optional.

Who it's for

Mockzilla is a strong candidate for developers coordinating frontend work against evolving APIs, teams testing failure handling, and CI users who want a mock environment per pull request. Its schema validation and proxy fallback are especially useful when a real service is incomplete. It is a poor fit for workflows that require uploading sensitive data, or for anyone who needs API access on a no-cost plan.

Pros and cons

• Pros: OpenAPI response generation and request validation help keep mock behavior tied to an API contract.
• Pros: Fault injection, proxy fallback, and request replay cover several practical integration-testing needs.
• Pros: The CLI runs offline, and the GitHub Action automates per-PR mock URLs and cleanup.
• Cons: Free has no API access and keeps request history for only two hours.
• Cons: The terms rule out sensitive uploaded content, limiting use with real customer or payment data.
• Cons: Paid plans impose request, rate, simulation and transfer caps, so teams with heavier usage may need Enterprise sizing.

Alternatives

API Mocking Tools is the broader category directory for comparing options. Choose Microcks instead if a fully open-source, community-driven CNCF Incubating project is the priority. MockServer is a free and open-source alternative for self-hosting without a SaaS account. WireMock offers a free plan and a free trial, and is worth comparing when those access terms matter. Knockout API is another freemium API option, with a free allowance of 30 images per month and metered pay-as-you-go pricing. Mockfly offers a free Starter plan capped at 500 requests per day, one project, four endpoints and two responses per endpoint. moqapi.dev offers a free mode with three projects, unlimited mock endpoints and all features unlocked, making it worth a look when project count matters more than a monthly request quota. WireMock is a second WireMock listing with a free plan and free trial. MockAPI has a free plan limited to one project and two resources, with paid monthly and annual options for 20 projects and 50 resources.

Verdict

Choose Mockzilla if you need schema-aware mocks, deliberate failure testing and pull-request environments across local work and CI. The combination is the main reason to pay for it; the main reasons to look elsewhere are the Free plan’s lack of API access, its two-hour history retention and the strict ban on sensitive uploads.