apimock-rs (API Mock)

Build a working REST API in seconds — without a backend.

Frontend blocked by an unfinished backend ? Need stable API responses for UI tests or offline development ?

Drop JSON files into a folder and your API immediately exists.

Quick start

Easy to start with npm package.

# install into your app project
npm install -D apimock-rs
# and go
npx apimock

# just use folders and JSON
mkdir -p api/v1/
echo '{"hello": "world"}' > api/v1/hello.json
npx apimock

# response
curl http://localhost:3001/api/v1/hello
# --> {"hello":"world"}

You may also check it out with browser to visit http://localhost:3001/api/v1/hello .

You now have a running REST endpoint.

Customization

Also, there's room to tweak things later with optional config file(s):

npx apimock --init

Vite project integration

An example of scripts section in package.json is as below.

concurrently is used to run the Vite and API mock servers simultaneously, while cross-env enables terminal output coloring. Before starting, ensure you run:

npm install -D concurrently cross-env

Edit package.json:

  "scripts": {
    "apimock": "npx apimock",
    "dev": "cross-env CLICOLOR_FORCE=1 concurrently \"vite\" \"npm run apimock\""
  }

Run:

npm run dev

npx apimock variation

| command | result | | --- | --- | | npx apimock | Run with all default parameters. | | npx apimock -p 4000 | Run with custom port. | | npx apimock -d tests/apimock-dyn-route | Run with custom root dir on server response. | | npx apimock -c apimock.toml | Run with config file giving rich features. Running npx apimock --init beforehand is required. |

Mock APIs easily 🎈 — just JSON and go

If you’re building or testing APIs, this tool makes mocking painless. It’s super fast, efficient, and flexible when you need it to be. All you have to do to start up is just use folders and JSON without any config set.

• ❄️ Zero-config start.
• 🌬️ Fast to boot, light on memory.
• 🪄 File-based and rule-based matching. Scripting supported.

When to use apimock-rs ?

• The backend is not ready yet.
• You need stable API responses for UI testing.
• You want offline development.
• CI tests require a predictable API.
• Your mock data is becoming large.

Handles real project scale

As your project grows, your mock API grows, too. Large mock datasets often cause problems:

• Slow startup
• High memory usage
• Crashes during UI testing
• Unstable CI runs

apimock-rs does not preload responses. Each response file is read only when a request arrives using non-blocking I/O. This keeps:

• Startup nearly instant
• Memory usage minimal
• Stable behavior under repeated requests

as validated with k6 load testing. You can run UI development and automated tests continuously without worrying about server instability.

📖 Documentation

For more details, 🧭 check out the docs.

Open-source, with care

This project is lovingly built and maintained by volunteers.
We hope it helps streamline your API development.
Please understand that the project has its own direction — while we welcome feedback, it might not fit every edge case 🌱

Acknowledgements

Depends on tokio / hyper / toml / serde / serde_json / json5 / console / rhai. In addition, mdbook (as to workflows).