Is it safe to paste API responses or config with secrets?
Yes. Formatting happens entirely in your browser, and nothing you paste is sent to a server. You can disconnect from the internet after the page loads and it still works.
Why does it say my JSON is invalid?
The most common causes are trailing commas, single quotes instead of double quotes, unquoted keys and comments. JSON allows none of these. The status line points to where the parser stopped.
What does “Sort keys” do?
It orders the keys of every object alphabetically, at every level. Arrays keep their order. This makes two JSON documents much easier to compare.
Does it change my data?
No. Only whitespace and, if you choose, key order change. Numbers are copied exactly as written, so 12345678901234567890 stays 12345678901234567890 and 1.0 stays 1.0. Many online formatters round big numbers like that because they go through JavaScript numbers.
What does “Fix mistakes” repair?
Text that is almost JSON, such as a JavaScript object or a Python dictionary: comments, single quotes, keys without quotes, trailing commas, missing commas between items, True, False and None, NaN, and hex numbers. The status line lists what was fixed. Strings and numbers are otherwise kept as written.