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Java Properties File Formatter

DataDeveloperText

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INPUT

Auto Process

OUTPUT

Client Side

Formatted Output

▶ Java .properties Format Reference

Java .properties files store configuration as flat key=value pairs. They are widely used by Java SE, Spring Boot, Logback, Hibernate, and ResourceBundle for i18n.

Separators

Keys and values can be separated by =, :, or whitespace. Whitespace around the separator is ignored.

Comments

Lines starting with # or ! are comments. Inline comments after a value are not supported by the spec.

Line Continuations

A line ending with a single backslash \ continues onto the next line. Leading whitespace on the continuation line is stripped.

Escapes

Standard escapes: \n, \t, \r, \f, \\, \=, \:, \ . Unicode escapes use \uXXXX with exactly four hex digits.

No Sections

Unlike INI, .properties has a flat namespace. Hierarchy is conveyed through dotted keys, e.g. spring.datasource.url.

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Guide

Java Properties File Formatter

This tool formats Java .properties files using the same rules the JDK uses to load them. It accepts =, :, or whitespace as a separator, recognises both # and ! comment styles, and joins backslash continuation lines into clean single-line key/value pairs. Use it on application.properties, logback.properties, ResourceBundle messages_*.properties, or any plain Java config you need to tidy up.

How to Use

Paste your raw .properties content into the input box (or click Try an example).
Pick a separator style: =, :, or preserve whatever the original line used.
Choose spacing around the separator and a comment style (#, !, or preserve).
Toggle options to sort keys, drop duplicates (keeping the last occurrence), align keys to a common width, trim trailing whitespace, or collapse repeated blank lines.
Copy the formatted output, or download it as a .properties file. The validation panel flags duplicate keys and malformed \uXXXX escapes.

Features

Spec-correct parsing – handles =, :, whitespace separators, and backslash line continuations the same way java.util.Properties does.
Comment style normalization – convert all comments to # or !, or preserve each line’s original prefix.
Sort and dedupe – alphabetise keys and drop earlier duplicates so the last occurrence wins (matching JVM load order).
Key alignment – pad keys to equal width for visually clean diffs and reviews.
Whitespace cleanup – trim trailing whitespace and collapse runs of blank lines.
Validation – warns on duplicate keys and reports invalid \uXXXX unicode escapes.
Live updates – output and validation refresh as you type or change options.