Pretty, powerful, flexible JSON generation.

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Pretty-print your JSON in Ruby or JavaScript or Lua with more power than is provided by JSON.pretty_generate (Ruby) or JSON.stringify (JS). For example, like Ruby's pp (pretty print), NeatJSON can keep objects on one line if they fit, but break them over multiple lines if needed.
  • Online webpage for performing conversions and experimenting with options.
Modifying graphical options on the webpage also gives you the JS code you would need to call to get the same results.
  • Keep multiple values on one line, with variable wrap width.
  • Format numeric values to specified decimal precision.
Optionally force specific keys to use floating point representation instead of bare integers for whole number values (e.g. 42.0 instead of 42).
  • Sort object keys to be in alphabetical order.
  • Arbitrary whitespace (or really, any string) for indentation.
  • "Short" wrapping uses fewer lines, indentation based on values. (See last example below.)
  • Indent final closing bracket/brace for each array/object.
  • Adjust number of spaces inside array/object braces.
  • Adjust number of spaces before/after commas and colons (both for single- vs. multi-line).
  • Line up the values for an object across lines.
  • Lua only Produce Lua table serialization.

Table of Contents


  • Ruby: gem install neatjson
  • JavaScript (web): Clone the GitHub repo and copy javascript/neatjson.js
  • Node.js: npm install neatjson


~ ruby require 'neatjson' json = JSON.neatgenerate( value, options ) ~
JavaScript (web):
~ html ~
~ js const { neatJSON } = require('neatjson'); var json = neatJSON( value, options ); ~
~ lua local neatJSON = require'neatjson' local json = neatJSON(value, options) ~


The following are all in Ruby, but similar options apply in JavaScript and Lua.
~ ruby require 'neatjson'
o = { b:42.005, a:42,17
, longer:true, str:"yes\nplease" }
puts JSON.neatgenerate(o)
=> {"b":42.005,"a":42,17,"longer":true,"str":"yes\nplease"}
puts JSON.neat
generate(o, sort:true)
=> {"a":42,17,"b":42.005,"longer":true,"str":"yes\nplease"}
puts JSON.neatgenerate(o,sort:true,padding:1,aftercomma:1)
=> { "a": 42, 17 , "b":42.005, "longer":true, "str":"yes\nplease" }
puts JSON.neatgenerate(o, sort:true, wrap:40)
=> {
=> "a":42,17,
=> "b":42.005,
=> "longer":true,
=> "str":"yes\nplease"
=> }
puts JSON.neat
generate(o, sort:true, wrap:40, decimals:2)
=> {
=> "a":42,17,
=> "b":42.01,
=> "longer":true,
=> "str":"yes\nplease"
=> }
puts JSON.neatgenerate(o, sort:->(k){ k.length }, wrap:40, aligned:true)
=> {
=> "a" :42,17,
=> "b" :42.005,
=> "str" :"yes\nplease",
=> "longer":true
=> }
puts JSON.neat
generate(o, sort:true, wrap:40, aligned:true, aroundcolon:1)
=> {
=> "a" : 42,17,
=> "b" : 42.005,
=> "longer" : true,
=> "str" : "yes\nplease"
=> }
puts JSON.neat
generate(o, sort:true, wrap:40, aligned:true, aroundcolon:1, short:true)
=> {"a" : 42,17,
=> "b" : 42.005,
=> "longer" : true,
=> "str" : "yes\nplease"}
a = 1,2,3,4,5
puts JSON.neatgenerate(a)puts JSON.prettygenerate(a) # oof!
=> 1,
=> 2,
=> 3,
=> 4,
=> 5
puts JSON.neatgenerate( a, wrap:true, short:true )
=> 1,
=> 2,
=> 3,
=> 4,
=> 5
data = "foo","bar",{dogs:42,piggies:{color:'pink', tasty:true},
opts = { short:true, wrap:60, decimals:3, sort:true, aligned:true,
padding:1, after_comma:1, around_colon_n:1 }
puts JSON.neat
generate( data, opts )
=> "bar",
=> { "barn" : { "hot" : "pajammy",
=> "jammy" : 3.142,
=> "jimmy" : 1, 2, 3, 4, 5 },
=> "cats" : 7,
=> "dogs" : 42,
=> "piggies" : { "color":"pink", "tasty":true } }


You may pass any of the following options to neat_generate (Ruby) or neatJSON (JavaScript/Lua). Note: option names with underscores below use camelCase in JavaScript and Lua. For example:
~ ruby
json = JSON.neatgenerate myvalue, arraypadding:1, aftercomma:1, beforecolonn:2 ~
~ js // JavaScript var json = neatJSON( myValue, { arrayPadding:1, afterComma:1, beforeColonN:2 } ); ~
~ lua -- Lua local json = neatJSON( myValue, { arrayPadding=1, afterComma=1, beforeColonN=2 } ) ~
  • wrap — Maximum line width before wrapping. Use false to never wrap, true to always wrap. default:80
  • indent — Whitespace used to indent each level when wrapping. default:" " (two spaces)
  • indent_last — Indent the closing bracket/brace for arrays and objects? default:false
  • short — Put opening brackets on the same line as the first value, closing brackets on the same line as the last? default:false
This causes the indent and indent_last options to be ignored, instead basing indentation on array and object padding.
  • sort — Sort objects' keys in alphabetical order (true), or supply a lambda for custom sorting. default:false
If you supply a lambda to the sort option, it will be passed three values: the (string) name of the key, the associated value, and the object being sorted, e.g. { sort:->(key,value,hash){ Float(value) rescue Float::MAX } }
  • aligned — When wrapping objects, line up the colons (per object)? default:false
  • decimals — Decimal precision for non-integer numbers; use false to keep values precise. default:false
  • trim_trailing_zeros — Remove extra zeros at the end of floats, e.g. 1.2000 becomes 1.2. default:false
  • force_floats — Force every integer value written to the file to be a float, e.g. 12 becomes 12.0. default:false
  • force_floats_in — Specify an array of object key names under which all integer values are treated as floats.
For example, serializing {a:[1, 2, {a:3, b:4}], c:{a:5, d:6} with force_floats_in:['a'] would produce {"a":[1.0, 2.0, {"a":3.0, "b":4}], "c":{"a":5.0, "d":6}}.
  • array_padding — Number of spaces to put inside brackets for arrays. default:0
  • object_padding — Number of spaces to put inside braces for objects. default:0
  • padding — Shorthand to set both array_padding and object_padding. default:0
  • before_comma — Number of spaces to put before commas (for both arrays and objects). default:0
  • after_comma — Number of spaces to put after commas (for both arrays and objects). default:0
  • around_comma — Shorthand to set both before_comma and after_comma. default:0
  • before_colon_1 — Number of spaces before a colon when the object is on one line. default:0
  • after_colon_1 — Number of spaces after a colon when the object is on one line. default:0
  • before_colon_n — Number of spaces before a colon when the object is on multiple lines. default:0
  • after_colon_n — Number of spaces after a colon when the object is on multiple lines. default:0
  • before_colon — Shorthand to set both before_colon_1 and before_colon_n. default:0
  • after_colon — Shorthand to set both after_colon_1 and after_colon_n. default:0
  • around_colon — Shorthand to set both before_colon and after_colon. default:0
  • lua — (Lua only) Output a Lua table literal instead of JSON? default:false
  • emptyTablesAreObjects — (Lua only) Should {} in Lua become a JSON object ({}) or JSON array ([])? default:false (array)

You may omit the 'value' and/or 'object' parameters in your sort lambda if desired. For example:
~ ruby
Ruby sorting examples
obj = {e:3, a:2, c:3, b:2, d:1, f:3}
JSON.neatgenerate obj, sort:true # sort by key name
=> {"a":2,"b":2,"c":3,"d":1,"e":3,"f":3}
generate obj, sort:->(k){ k } # sort by key name (long way)
=> {"a":2,"b":2,"c":3,"d":1,"e":3,"f":3}
JSON.neatgenerate obj, sort:->(k,v){ -v,k } # sort by descending value, then by ascending key
=> {"c":3,"e":3,"f":3,"a":2,"b":2,"d":1}
JSON.neatgenerate obj, sort:->(k,v,h){ h.values.count(v) } # sort by count of keys with same value
=> {"d":1,"a":2,"b":2,"e":3,"c":3,"f":3}
~ js // JavaScript sorting examples var obj = {e:3, a:2, c:3, b:2, d:1, f:3};
neatJSON( obj, {sort:true} ); // sort by key name // {"a":2,"b":2,"c":3,"d":1,"e":3,"f":3}
neatJSON( obj, { sort:function(k){ return k }} ); // sort by key name (long way) // {"a":2,"b":2,"c":3,"d":1,"e":3,"f":3}
neatJSON( obj, { sort:function(k,v){ return -v }} ); // sort by descending value // {"e":3,"c":3,"f":3,"a":2,"b":2,"d":1}
var countByValue = {}; for (var k in obj) countByValueobjk
= (countByValueobjk||0) + 1; neatJSON( obj, { sort:function(k,v){ return countByValuev } } ); // sort by count of same value // {"d":1,"a":2,"b":2,"e":3,"c":3,"f":3} ~
Note that the JavaScript and Lua versions of NeatJSON do not provide a mechanism for cascading sort in the same manner as Ruby.

License & Contact

NeatJSON is copyright ©2015–2022 by Gavin Kistner and is released under the MIT License
. See the LICENSE.txt file for more details.
For bugs or feature requests please open issues on GitHub1. For other communication you can email the author directly.

TODO (aka Known Limitations)

  • Figure out the best way to play with custom objects that use to_json for their representation.
  • Detect circular references.
  • Possibly allow "JSON5" output (legal identifiers unquoted, etc.)


  • v0.10.5 — November 17, 2022
Fix issue #21: Strings containing # get an invalid escape added (Ruby only)
  • v0.10.4 — November 17, 2022
Online tool shows input/output bytes
  • v0.10.2 — August 31, 2022
Fix bugs found in JavaScript version related to trim_trailing_zeros.
  • v0.10.1 — August 29, 2022
Fix bugs found when force_floats_in was combined with wrapping. Update interactive HTML tool to support new features.
  • v0.10 — August 29, 2022
Add force_floats and force_floats_in to support serialization for non-standard parsers that differentiate between integers and floats. Add trim_trailing_zeros option to convert the decimals output from e.g. 5.40000 to 5.4. Convert JavaScript version to require ECMAScript 6 for performance.
  • v0.9 — July 29, 2019
Add Lua version, serializing to both JSON and Lua table literals All languages serialize Infinity/-Infinity to JSON as 9e9999 and -9e9999 All languages serialize NaN to JSON as "NaN"
  • v0.8.4 — May 3, 2018
Fix issue #27: Default sorting fails with on objects with mixed keys Ruby only
* _Thanks Reid Beels_
  • v0.8.3 — February 20, 2017
Fix issue #25: Sorting keys on multi-line object using function does not work without "short" JS only
* _Thanks Bernhard Weichel_
  • v0.8.2 — December 16th, 2016
Fix issue #22: Sorting keys on multi-line object does not work without "short" JS only Update online interface to support tabs as well as spaces. Update online interface to use a textarea for the output (easier to select and copy). Update online interface turn off spell checking for input and output.
  • v0.8.1 — April 22nd, 2016
Make NeatJSON work with Opal (by removing all in-place string mutations)
  • v0.8 — April 21st, 2016
Allow sort to take a lambda for customized sorting of object key/values.
  • v0.7.2 — April 14th, 2016
Fix JavaScript library to support objects without an Object constructor (e.g. location). Online HTML converter accepts arbitrary JavaScript values as input in addition to JSON.
  • v0.7.1 — April 6th, 2016
Fix Ruby library to work around bug in Opal.
  • v0.7 — March 26th, 2016
Add indentLast/indent_last feature.
  • v0.6.2 — February 8th, 2016
Use memoization to avoid performance stalls when wrapping deeply-nested objects/arrays.
_Thanks @chroche_
  • v0.6.1 — October 12th, 2015
Fix handling of nested empty objects and arrays. (Would cause a runtime error in many cases.)
* _This change causes empty arrays in a tight wrapping scenario to appear on a single line where they would previously take up three lines._
  • v0.6 — April 26th, 2015
Added before_colon_1 and before_colon_n to distinguish between single-line and multi-line objects.
  • v0.5 — April 19th, 2015
Do not format integers (or floats that equal their integer) using decimals option. Make neatJSON() JavaScript available to Node.js as well as web browsers. Add (Node-based) testing for the JavaScript version.
  • v0.4 — April 18th, 2015
Add JavaScript version with online runner.
  • v0.3.2 — April 16th, 2015
Force YARD to use Markdown for documentation.
  • v0.3.1 — April 16th, 2015
Remove some debugging code accidentally left in.
  • v0.3 — April 16th, 2015
Fix another bug with short:true and wrapping array values inside objects.
  • v0.2 — April 16th, 2015
Fix bug with short:true and wrapping values inside objects.
  • v0.1 — April 15th, 2015
Initial release.