JSON viewer

Firefox includes a JSON viewer. If you open a JSON file in the browser, or view a remote URL with the Content-Type set to application/json, it is parsed and given syntax highlighting. Arrays and objects are shown collapsed, and you can expand them using the “+” icons.

JSON Lines documents (one JSON value per line, .jsonl files, or responses served as application/jsonl, application/jsonlines or application/x-ndjson) are also recognized. The document is displayed like a JSON array, with one independently collapsible entry per non-blank line, in document order (blank lines are skipped, so entry indices don’t necessarily match file line numbers). A line that isn’t valid JSON is shown inline as an error without affecting the rest of the document. Pretty-printing is not offered for JSON Lines documents, since each record is already on its own line.

The JSON viewer provides a search box that you can use to filter the JSON.

You can also view the raw JSON and pretty-print it.

Finally, if the document was the result of a network request, the viewer displays the request and response headers.

Console API

The JSON viewer exposes data through a console API, making it easy to access the parsed JSON and other information from the Console:

• $json.data - The parsed JSON object

• $json.text - The original JSON text

• $json.headers - HTTP request and response headers

To access these from the console, open the Web Console, and type $json.data to explore the parsed JSON object.