APIs and browser network tabs often return JSON as one long unreadable line. A JSON formatter extension rewrites that page into an indented, color-coded tree the moment it loads, so developers, testers and support staff can scan a response, collapse sections and find a specific field without leaving the browser.
What a JSON formatter extension does
A JSON formatter chrome extension detects when a tab's content type is JSON and re-renders it as an indented, syntax-highlighted tree instead of a single line of text. Most let you collapse and expand nested objects and arrays, search within the data and switch back to the raw, unformatted response when you need to copy it exactly.
JSON formatter vs a JSON viewer
The terms are mostly used interchangeably: a JSON viewer chrome extension and a JSON formatter chrome extension both take raw JSON and make it readable. Some tools add extra viewer features such as a table view for arrays of objects or a dark theme, but the core job of formatting nested data is the same.
When you don't need an extension
Chrome's DevTools Network tab already pretty-prints JSON responses when you click the Preview tab on a request, so occasional debugging doesn't require installing anything. An extension earns its place when you regularly open raw JSON URLs directly, or want formatting to apply automatically on every page load.