JSON strings, escaped correctly.

Worked examples

JSON inside JSON. The text {"id":7,"note":"a\nb"} (with a literal backslash and n) escapes to "{\"id\":7,\"note\":\"a\\nb\"}". Parse that once and you get the inner text back; parse the inner text and you get the object.

JS and C# source. The output uses only \" \\ \b \f \n \r \t and \uXXXX, which are also string escapes in JavaScript and in C# regular (non-verbatim) string literals, so a wrapped result can be pasted into source code. ECMAScript has accepted U+2028 and U+2029 inside string literals since ES2019, so they need no special case. In a C# verbatim string (@"...") you would instead double each quotation mark.

Rules used

Per RFC 8259 section 7, quotation mark, backslash and U+0000 to U+001F must be escaped. Control characters without a short form are written \u00XX. Characters outside the Basic Multilingual Plane are written as a UTF-16 surrogate pair (the RFC example is U+1D11E as \uD834\uDD1E). Unpaired surrogates are always escaped here, since they cannot be encoded as valid UTF-8. The slash is optional and off by default. Unescaping accepts the nine escapes in the RFC grammar (\" \\ \/ \b \f \n \r \t \uXXXX) and reports the line, column and offset of the first violation.

Sources: RFC 8259, The JSON Data Interchange Format (December 2017); TC39 JSON superset proposal (ES2019); Microsoft C# escape sequences. Rules checked against the RFC text 2026-10-01.

FAQ

Which characters must be escaped?

Quotation mark, backslash and U+0000 to U+001F. Nothing else is required.

Do I need to escape the forward slash?

No. \/ is legal but a bare slash is also valid; some serializers escape it to keep </script> out of inline HTML.

How do emoji appear in ASCII-only output?

As a surrogate pair of two \uXXXX escapes, 12 characters in total.

Is this the same as JSON.stringify?

With default options the output matches JSON.stringify on a string, except that hex digits are uppercase (both are valid).