Unminify JS (Javascript)

What unminifying JavaScript means

Minifiers remove whitespace, line breaks and comments from JavaScript to make the file smaller. They may also shorten local variable names and restructure expressions. Unminifying, or beautifying, reverses the cosmetic part: it puts indentation and line breaks back so a human can read the code.

This page runs the JavaScript you paste through a formatter and returns indented output. It does not execute the code, repair it or rebuild the original source. The result is the same program in a more readable layout.

What the formatter restores

Whitespace and line structure are the main gain. A minified file that arrives as one long line becomes a sequence of indented statements and blocks. That makes it possible to follow braces, conditionals, loops and function boundaries.

Strings and syntax stay as they were. The formatter does not change the logic, add missing semicolons or fix a bug. If the minified file was valid, the output should behave the same way when run; if it was broken, formatting will not repair it.

You can also switch the mode selector to minify if you need the reverse operation, and the language selector supports HTML, CSS, JavaScript, SQL, XML, JSON and PHP. This page opens in JavaScript beautify mode because that is the common unminify use case.

What it cannot restore

Minification often renames local variables to short letters and removes comments. Beautifying cannot recover the original names or the deleted comments. A variable called a stays a; you have to infer its meaning from how it is used.

Source maps are separate files that map minified positions back to the original source. This tool does not read or apply source maps. If the site publishes a map, use the browser\'s developer tools to load it; that gives you the real original file, not a reformatted guess.

Property names, public API names and string contents are usually preserved by minifiers because changing them would break the program. They may still be cryptic, but they are the best clues you have when reading the output.

How to use the page

Paste the minified JavaScript into the input panel. You can also paste a URL into the URL field and submit it to fetch the code, if the file is publicly reachable and the server can access it. Then press Process Code.

The server formats the code and returns it to the output panel. Use Copy to put it on your clipboard, or Download to save a file. Clear All resets the panels for the next run.

Format a copy, never the only copy of a production file. Keep the original minified asset so you can compare behaviour and restore it if an edit goes wrong.

Reading the output

Start at the top-level functions and look for event listeners, network calls and configuration objects. Names such as fetch, addEventListener and JSON.parse survive minification and give you anchors.

Follow the data rather than the names. A short variable that receives the result of a form submission is probably the payload, even if it is called e or t. Add your own notes in a separate file; do not rename things and expect the program to keep working without testing.

Be careful with automatic formatting of very large bundles. A single 5 MB vendor file can be slow to process and painful to read. Extract the function or module you need rather than trying to beautify an entire application at once.

Why unminify code

Developers unminify to debug a production issue, audit a third-party script, learn how a library works or check what a tracking snippet actually sends. A readable layout makes it easier to spot a hard-coded endpoint, a suspicious redirect or an unexpected event handler.

It is also useful for teaching and code review when the only available copy is minified. The output is not the original source, but it is far easier to discuss than one enormous line.

Limits and security

The code is sent to the server for formatting. Do not paste API keys, access tokens, passwords, private customer data or proprietary source you are not allowed to share. A public formatter is not a secure code vault.

The tool does not run the JavaScript, so it cannot tell you whether the code is safe or whether it works. Formatting is not a malware scan, a dependency audit or a licence review. Treat unknown code with the same caution you would use for any downloaded script.

Very large inputs can hit request limits or time out. Split the file or extract the relevant section if processing fails.

What changes between minified and beautified code

Minified code often arrives as one very long line with no indentation and single-letter local names. Beautified code spreads the same statements across lines, indents nested blocks and makes the control flow visible. The program logic does not change.

A line-by-line comparison between the two versions is rarely useful because the layout is completely different. Compare behaviour, inputs and outputs instead. If you edit the beautified copy, run the same tests you would run on any code change.

Source maps and original files

A source map is a separate file that points minified positions back to the original source. If the site publishes one, the browser developer tools can load the real file, which is better than any beautifier. Look for a map reference at the end of the minified file or in the network panel.

When no map exists, beautifying is the best available option. It gives you structure but not the original names, comments or module boundaries. Treat the result as a readable reconstruction, not the source of record.

Common mistakes

Editing a beautified bundle and deploying it without tests, renaming short variables and breaking references, pasting a file that contains secrets, and trying to format an entire vendor bundle in one pass are the usual problems. Work on a copy, isolate the function you need and keep the original asset.

Formatting is also not a security review. A readable script can still be malicious, and an ugly one can be harmless. Read what it does, check the network calls and do not run unknown code just because it looks organised.

Frequently Asked Questions