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A simple command-line JSON server that also emulates a REST API. If you need to stub out an API locally, this is the tool you need. It's lightweight, works on Mac, Windows, and Linux, and requires no setup other than a JSON data file.


Create a JSON file called data.json:

  "notes" : [
      "id" : 1,
      "title" : "Hello World"
      "id" : 2,
      "title" : "The second note"

Then run demo-api. The server starts up.

Visit http://localhost:8080 in the browser to serve the entire file as a JSON response.

In addition, since the JSON file is structured like a typical REST API data structure, the following endpoints will work:

  • GET http://localhost:8080/notes - retrive all "notes"
  • GET http://localhost:8080/notes/1 - retrive the note with the id of 1
  • POST http://localhost:8080/notes/ with JSON payload - Create a new note. This modifies the data.json file.
  • PUT/PATCH http://localhost:8080/notes/1 with JSON payload - update the note with the id of 1. This modifies the data.json file.
  • DELETE http://localhost:8080/notes/1 - Delete the note with the id of 1. This modifies the data.json file.

Anything that doesn't match returns a 404 status code.

Examples with curl

Given the following data file:

  "notes" : [
      "id" : 1,
      "title" : "Hello World"
      "id" : 2,
      "title" : "The second note"

To get everything:

curl -i localhost:8080/

To get the notes node:

curl -i localhost:8080/notes

To get the notes/1 node:

curl -i localhost:8080/notes/1

To add a new note:

curl -i -X POST http://localhost:8080/notes \
-H "Content-type: application/json" \
-d '{"title": "This is another note"}'

To update the contents of the first note:

curl -i -X PUT http://localhost:3000/notes/1  \
-H "Content-type: application/json" \
-d '{"title": "This is the third note"}'

To delete the third note:

curl -i -X DELETE localhost:3000/notes/3

If you use a different JSON file, your paths will be different.

Advanced Usage

To specify a different port, use the -p option:

demo-api -p 4000

To specify a different filename, in case you don't like data.json as the default, use -f and specify the file:

demo-api -f notes.json

To view the version, use -v:

demo-api -v


To install, download the latest release to your system and copy the executable to a location on your path. Then launch it in a directory containing data.json.


  • Refactoring. This code is a mess.
  • A "no persist" mode - changes are accepted but not saved to the JSON file.


Please contribute.

Clone the repository and then download the dependencies:

$ go get
$ go get
$ go get

Run development version:

$ gin --appPort 8080 go run app.go

The server is now listening on localhost:3000 and will reload on code change.

Make changes, run the tests, create a PR.


  • 2018-09-03 - v0.3.0
    • Refactoring to make testing possible
    • Adds test suite
    • Pretty print
    • Supports PUT and PATCH
    • Supports -v option to show version
    • Supports -f option to specify the data file
    • Supports -p option to specify the port
    • Fix bug where querying non-existant ID still returned a 200 status code instead of 404
  • 2018-08-30 - v0.1.0
    • initial release


Apache 2. See LICENSE file.


A lightweight local http server with CORS support that serves JSON data via a REST API. Great for testing stuff.








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