JSON string escaper

This JSON string escaper converts plain text into the escaped form required inside a JSON string value, and it reverses the same mapping when you paste escaped content back into ordinary characters. Encoding rewrites double quotes, backslashes, and control characters so a hand-built payload, template, or log line can sit safely between JSON quotes without breaking the surrounding document. Decoding accepts the standard JSON escapes—quote, backslash, optional slash, the short forms for backspace form-feed newline return and tab, and four-digit u-escapes—and it fails loudly on incomplete sequences, illegal backslash pairs, raw double quotes inside the content, or bare control characters so typos never silently survive into production.

What JSON string escaping is and what this tool returns

A literal double quote must appear as a backslash-quote pair, a literal backslash must be doubled, and every control character in the U-plus-zero-zero-zero-zero through U-plus-zero-zero-one-F range must be written as a short escape when one exists or as a four-digit u-escape otherwise. A JSON string value is delimited by double quotes, and the characters that may appear between those quotes are constrained by ECMA-404 and the common JSON.stringify rules used across languages. This page implements that encode set on the encode path and the reverse on decode: the response is the string content only, without adding or removing the outer quotes of a full JSON document. The JSON response always includes result for the transformed string, mode echoing encode or decode, encoding fixed to json_string, and input_length plus output_length so tests can assert sizes. Encode also reports escapes_applied and decode reports escapes_resolved so you can confirm how many special characters or escape sequences were rewritten. There is no partial silent skip for a broken sequence: either every backslash pair is legal JSON or the request fails with invalid_input.

How text and mode are read and how results stay reproducible

Decode scans for backslash-led sequences: quote, backslash, slash, the five short control forms, and u followed by exactly four hexadecimal digits. The preferred payload field is text, with aliases input, value, s, and payload so forms, query strings, and SDK clients can reuse the same contract without renaming columns. Mode defaults to encode and accepts decode explicitly; aliases op, direction, and action map to the same switch for scripts that already use those names, and escape or unescape are accepted as synonyms. Encode walks the string by UTF-16 code units and replaces only the characters that JSON requires to be escaped, leaving letters, digits, and ordinary Unicode unchanged so readable copy stays readable. Because backslash is rewritten in the same left-to-right pass as quotes and controls, you get a single consistent escaping pass that matches the character rules of JSON.stringify for string content. An incomplete trailing backslash, a short escape that is not in the JSON set, a u-escape without four hex digits, a raw double quote, or a bare control character raises invalid_input with a message that names the problem. The length ceiling of one hundred thousand characters keeps Worker memory predictable while still covering templates, sample payloads, and most paste buffers. Pair the free browser run on this page with the priced API when you need the identical mapping inside an automated pipeline without re-implementing JSON string tables yourself. Invalid inputs return invalid_input and are not charged, which keeps validation cheap while successful transforms remain a fixed item price at $0.002.

Where JSON string escape and unescape fit in developer workflows

Pipeline authors decode entity-heavy or escape-heavy exports from legacy systems so application code works with true newlines and quotes instead of literal backslash-n sequences. Frontend and backend teams encode dynamic titles and labels before placing them inside a quoted JSON field so a single quote, backslash, or newline cannot break the surrounding document. Quality engineers generate deterministic encode and decode pairs for contract tests so a middleware that claims JSON string support cannot silently switch to a non-standard escape table between releases. Educators use the same tool when teaching the difference between a full JSON document, a JSON string value, and the small set of escapes that the specification allows inside that value. On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split—free interactive exploration and a priced, identical API—matches the rest of the KIT tier-A catalog and lets you move from a classroom demo to an automated pipeline without changing the escaped result. Pair it with URL percent-encoding or XML entity helpers when you need broader text transforms, and with other encoding endpoints when you are building a small lab of free, deterministic tools for CI and documentation.