Which line formats are supported?

Both key=value and key:value separators are recognized, matching the two forms the Java Properties class accepts. Lines starting with # or ! are treated as comments and skipped.

How do dotted keys become nested JSON?

A key like app.name is split on its dots and used to build nested objects, so app.name=api and app.debug=false together produce {"app":{"name":"api","debug":"false"}}.

Are values converted to numbers or booleans?

No, every value is kept as a JSON string exactly as written, since .properties files have no type system to infer from.

Does this support line continuations with a trailing backslash?

Not currently; each key=value pair must fit on a single line. Multi-line values need to be joined manually before conversion.

Properties to JSON Converter - Convert .properties

Overview

Introduction

A Java .properties file is a flat list of key=value lines, convenient for JVM tooling but awkward to work with in JSON-based systems. This tool parses one back into a structured JSON document.

It recognizes the dot-notation convention frameworks like Spring Boot use for nested config, rebuilding that nesting as real JSON objects.

What Is Properties to JSON Converter?

A .properties parser that reads key=value (or key:value) lines, skips comment lines starting with # or !, and reconstructs a nested JSON object from dotted key paths.

It's the reverse of Convert JSON to Properties, though since .properties has no type system, all resulting values remain strings.

How Properties to JSON Converter Works

Each non-comment, non-blank line is split at its first unescaped = or : character into a key and a value; the value has its own escape sequences (\n, \r, \t, and backslash-escaped characters) decoded.

The key is then split on dots, and a nested object is built (or extended) at that path, so keys sharing a common prefix end up as sibling properties of the same nested object.

When To Use Properties to JSON Converter

Use it when migrating a Java or Spring Boot .properties config into a JSON-based system or JavaScript codebase.

It's also useful for quickly visualizing the nested structure a flat .properties file actually represents.

Often used alongside JSON to Properties Converter, CSV to JSON Converter and JSON Object Flattener.

Features

Advantages

Reconstructs nested JSON objects from dot-notation keys automatically.
Recognizes both = and : as valid separators, matching Java's own parser behavior.
Runs entirely client-side.

Limitations

Line continuations (a trailing backslash to join two lines) aren't supported; each entry must be a single line.
All values remain strings; there's no automatic conversion to numbers or booleans.

Examples

Parsing a flat config

Input

app.name=api
app.debug=false
replicas=3

Output

{
  "app": {
    "name": "api",
    "debug": "false"
  },
  "replicas": "3"
}

Dotted keys under the same prefix (app.*) become properties of a shared nested object.

Best Practices & Notes

Best Practices

Join any line-continuation entries in your source file into single lines before pasting, since continuations aren't parsed.
Convert string values to numbers or booleans in your own code afterward if your JSON consumer needs typed data.
Use Convert JSON to Properties afterward to verify a round trip preserves the same keys.

Developer Notes

The separator is located with a regex that uses a negative lookbehind, `(?<!\\)[=:]`, so an escaped \= or \: inside a key doesn't get mistaken for the key/value boundary; values are then unescaped for \n, \r, \t, and generic backslash-escaped characters before being written into the nested object at the key's dotted path.

Properties to JSON Converter Use Cases

Migrating a Spring Boot application.properties file into a JSON-based config system
Visualizing the nested structure implied by a flat Java properties file
Converting legacy JVM configuration for use in a JavaScript or Node.js project

Common Mistakes

Pasting a .properties file that relies on line continuations, which this parser doesn't currently join.
Expecting numeric or boolean values automatically; everything parses as a string.
Mixing = and : separators inconsistently and being surprised both are accepted identically.

Tips

If a key looks like it didn't nest correctly, check for an unescaped dot that wasn't meant to introduce nesting.
Pair with Convert JSON to Properties to confirm a clean round trip for your specific config.

Properties to JSON Converter