What's the file size limit?

The API endpoint accepts up to 1 MB of JSON per request. For larger files, run the formatter locally: node -e "console.log(JSON.stringify(JSON.parse(require('fs').readFileSync('input.json','utf8')),null,2))"

Yes — enable the 'Sort keys' option to sort object keys alphabetically at every level of nesting. Array element order is always preserved because arrays are ordered by definition.

How do I tell if a timestamp is in seconds or milliseconds?

Seconds timestamps for dates after 2001 are 10 digits (≥ 1,000,000,000). Milliseconds timestamps are 13 digits (≥ 1,000,000,000,000). This tool auto-detects: any number larger than 10,000,000,000 is treated as milliseconds.

What timezone does the output use?

All output is in UTC. Unix timestamps have no timezone — they always count seconds from the UTC epoch. The ISO 8601 string ends with 'Z' (Zulu / UTC). To display in a local timezone, use your application's date-formatting library with a timezone identifier (e.g. 'America/New_York').

Tool comparison

JSON Formatter vs Unix Timestamp Converter

JSON Formatter (formatting) and Unix Timestamp Converter (datetime) come from different categories but appear together in developer workflows. This guide explains what each does and when to reach for one over the other.

Bottom line

JSON Formatter displays the raw JSON structure, including epoch-second values as plain numbers. Timestamp Converter translates those numeric values into human-readable dates. Paste the JSON into the formatter to find the timestamp field, then paste the value into Timestamp Converter to read the date.

What each tool does

JSON Formatter

JSON (JavaScript Object Notation) is a lightweight text format for representing structured data using key-value pairs, arrays, strings, numbers, booleans, and null. It is the dominant data interchange format for REST APIs, configuration files, and data storage. A JSON formatter parses a JSON string and re-serializes it with consistent indentation and line breaks (pretty-print) to make it human-readable, or removes all whitespace (minify) to produce the smallest possible representation for transmission or storage. This tool goes further: it validates syntax and reports the exact line and column of any parse error, optionally sorts all object keys alphabetically for consistent diffs, and can repair common JSON-like inputs that are technically invalid — such as trailing commas, JavaScript-style comments, and single-quoted strings.

Open JSON Formatter →

Unix Timestamp Converter

A Unix timestamp (also called epoch time or POSIX time) is the number of seconds that have elapsed since 00:00:00 UTC on 1 January 1970 — a moment known as the Unix epoch. Timestamps are the universal language of time in software: databases store them as integers, APIs return them in JSON, log files record them for every event, and JWT tokens use them for 'iat' (issued-at) and 'exp' (expiry) claims. Unlike formatted date strings, Unix timestamps are unambiguous — they have no timezone, no locale, and no format variation. JavaScript and many APIs also use millisecond timestamps (Unix seconds × 1000). This tool converts in both directions: paste a timestamp to get a human-readable date in UTC and ISO 8601, or paste a date string to get the corresponding epoch seconds and milliseconds.

Open Unix Timestamp Converter →

Side-by-side comparison

Feature	JSON Formatter	Unix Timestamp Converter
Category	formatting	datetime
Primary purpose	Pretty-print or minify JSON — with syntax validation.	Convert Unix timestamps to human-readable dates and ISO 8601, or convert dates back to epoch seconds.
Inputs	json, mode, indent, sort_keys, repair	input, mode
Outputs	output, valid, error, error_line, error_column	unix_seconds, unix_ms, iso8601, utc, relative, valid, error

When to use each

Use JSON Formatter when…

How to pretty-print a JSON API response

Convert a minified or compact JSON API response into human-readable, indented output for inspection.

How to minify JSON for production

Remove all whitespace from a JSON file to reduce its size before embedding it in code, APIs, or config files.

Use Unix Timestamp Converter when…

How to convert a Unix timestamp to a readable date

Turn an epoch seconds value from a database, API, or log file into a human-readable date.

How to convert a date to a Unix timestamp

Get the Unix epoch seconds for a specific date to use in a database, API, or JWT.

Frequently asked questions

What's the file size limit?: The API endpoint accepts up to 1 MB of JSON per request. For larger files, run the formatter locally: node -e "console.log(JSON.stringify(JSON.parse(require('fs').readFileSync('input.json','utf8')),null,2))"
Does it sort keys?: Yes — enable the 'Sort keys' option to sort object keys alphabetically at every level of nesting. Array element order is always preserved because arrays are ordered by definition.
How do I tell if a timestamp is in seconds or milliseconds?: Seconds timestamps for dates after 2001 are 10 digits (≥ 1,000,000,000). Milliseconds timestamps are 13 digits (≥ 1,000,000,000,000). This tool auto-detects: any number larger than 10,000,000,000 is treated as milliseconds.
What timezone does the output use?: All output is in UTC. Unix timestamps have no timezone — they always count seconds from the UTC epoch. The ISO 8601 string ends with 'Z' (Zulu / UTC). To display in a local timezone, use your application's date-formatting library with a timezone identifier (e.g. 'America/New_York').