Mock Your API in 5 Minutes with JSON (No Backend Required)

Alejandro Rodriguez — Sun, 09 Aug 2026 16:47:50 +0000

Your frontend needs the API now. The backend isn’t ready, staging is down, or you want to trigger a 500 without asking anyone to break the server.

In this article you’ll:

Install a local mock server
Define an endpoint in a JSON file
Call it with curl (or from your app) as if it were the real API

This isn’t an embeddable SDK — it’s a CLI that boots HTTP on your machine. Your app talks to http://localhost:3001 the same way it would talk to staging.

Prerequisites

Node.js >= 22.12
A project with a package.json (recommended)

1. Install

npm install http-mock-json --save-dev

The CLI binary is mock-server.

2. Initialize

npx mock-server init

By default this will:

Create a mocks/ directory
Add a mock:start script to your package.json (mock-server start -p 3001)
Prompt you to create a first mock

For the prompts, you can use something like:

Prompt	Example
JSON file name	`animals` → `mocks/animals.json`
Endpoint	`data/animals`
Methods	`GET`

The scaffold sets nameResponse to "success" and includes two empty responses: success (200) and error (404).

3. Fill in the response bodies

Open mocks/animals.json and make it look like this:

{
  "data/animals": {
    "GET": {
      "nameResponse": "success",
      "responses": [
        {
          "name": "success",
          "statusCode": "200",
          "body": {
            "animals": [
              { "id": 1, "name": "Lion" },
              { "id": 2, "name": "Tiger" }
            ]
          }
        },
        {
          "name": "error",
          "statusCode": "404",
          "body": {
            "message": "No animals found"
          }
        }
      ]
    }
  }
}

What you need on day one:

Piece	Role
Top-level key	Endpoint path (`data/animals`)
Uppercase method	`GET`, `POST`, etc.
`nameResponse`	Which scenario is returned by default
`responses[]`	Named scenarios with `name`, `statusCode`, and `body`

4. Start the server

npx mock-server start

Or, if init added the script:

npm run mock:start

Both listen on port 3001 by default (http://localhost:3001).

On start, every mock file is validated. Errors block startup — fix them and run again.

Watch mode is always on: save a mock file and the server reloads.

5. Try it

curl -i http://localhost:3001/data/animals

(Use port 3001 if you started via the init script.)

You should see something like:

HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8

{"animals":[{"id":1,"name":"Lion"},{"id":2,"name":"Tiger"}]}

In your frontend, point the API base URL at that local host. Same HTTP calls — different “backend.”

10-second bonus: flip to the error scenario

Change this in the JSON:

"nameResponse": "error"

Save the file (watch reloads) and run curl again. You now get the 404 with the error message — without touching the frontend.

That’s the core idea: same URL, different backend behavior, controlled from JSON.

What you just got

A local mock server in minutes
An endpoint defined in a file the team can read and version
Success ↔ error by editing a single key

I Built a Free Planning Poker App with SvelteKit and Cloudflare Durable Objects

Alejandro Rodriguez — Sun, 09 Aug 2026 05:03:49 +0000

Scrum teams need Planning Poker often — and they rarely want another account, another SaaS login, or a shared spreadsheet.

So I built Planning Poker Free: open-source, no signup, create a room, share the link, and estimate in real time.

Live app: planningpoker.free
Source: github.com/alejandrorodrom/planning-poker-free

The problem

Most estimation tools ask for accounts, orgs, or paid seats before the team can vote. For a 15-minute refinement, that friction is too high.

I wanted something closer to:

Create a room
Share /room/{id}
Vote
Reveal and discuss

No accounts. Optional password. Done.

What it does

Rooms: public or password-protected
Roles: moderator, voter, observer (with handoff if the moderator drops)
Decks: modified Fibonacci, Fibonacci, powers of two, T-shirt, sequential
Aggregation: consensus, mode, median, or mean
Voting UX: hidden/revealed cards, optional auto-reveal
Teams: overall + per-team results
Export: Markdown, CSV, or a photo.

Stack

Layer	Choice
UI	Svelte 5
App framework	SvelteKit
Language	TypeScript
Runtime	Cloudflare Workers
Realtime state	Durable Objects + WebSockets

Each room is its own Durable Object: one in-memory state machine plus WebSocket fan-out. No Redis, no always-on Node process — the room wakes when people join and stays consistent while they’re connected.

That combo is the interesting part for me: realtime multiplayer UX without babysitting infrastructure.

Design choices that mattered

No accounts on purpose

Session rejoin uses localStorage so people can refresh and come back. Last active tab wins. Simple, good enough for estimation sessions.

Moderators can hand off

If the moderator goes offline, someone else can claim moderation. Real meetings are messy; the tool should survive that.

Export is not optional

After the call, teams want notes. Markdown/CSV export makes the session useful beyond the live board.

Try it

Open planningpoker.free
Create a room
Share the link with your team
Vote and reveal

If you find a bug or want a feature, open an issue or PR on GitHub.

What’s next

If you use it with your team, tell me what broke — or what you wished existed.

Built and maintained by Alejandro Rodriguez Romero / RODRIGUEZROM.

DEV Community: Alejandro Rodriguez