API Response Visualizer

The API Response Visualizer is a client-side tool that parses JSON API responses and displays them in a structured, readable format with a summary overview. When you paste a JSON response from a REST API, GraphQL endpoint, or any JSON-producing service, the tool parses it and generates two outputs: a high-level summary that describes the response structure (e.g., "Array with 50 items, first item keys: id, name, email") and the full prettified JSON with syntax highlighting in a dark-themed code view. The summary section is particularly useful for quickly understanding unfamiliar API responses — it identifies whether the top-level value is an array or object, counts the number of items or keys, lists the property names of the first few elements, and annotates nested structures with their types (Array[N] or Object{N}). For array responses, it inspects the first element's keys to help you understand the data shape before diving into individual records. The tool handles edge cases gracefully: non-JSON input is displayed as raw text with a character count, malformed JSON is caught and shown with an informative error message, and deeply nested structures are displayed without truncation. The visual output uses a styled HTML rendering with a dark background (Catppuccin-inspired theme), monospace font, and color-coded sections for the summary and full response. Everything runs in the browser — the response data is never sent to any external service.

When working with APIs, you frequently need to inspect responses — during development, debugging, documentation writing, or data migration. Raw JSON from an API is typically minified and impossible to read at a glance. While you could use browser DevTools or a JSON formatter, the API Response Visualizer adds value through its summary layer: instead of scrolling through a 500-line response to understand its shape, the summary tells you immediately that it is an array of 50 objects with keys like id, name, email, and address, and that the address field is a nested object with 4 properties. This structural overview is especially valuable when exploring a new API, reviewing webhook payloads, or debugging an unexpected response format. The tool also serves as a quick sanity check: if you paste a response expecting JSON and see "not valid JSON" in the info bar, you immediately know the API is returning HTML, an error page, or a malformed response. The dark-themed styled output makes it comfortable for extended use, and the entire workflow — paste, click, read — takes seconds.

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.

What happens if the input is not valid JSON?

<p>The tool catches the parse error and displays the raw input text as-is, with an info note indicating it is not valid JSON and showing the character count. This lets you quickly identify issues like truncated responses, HTML error pages, or text wrapped in extra quotes.</p>

Can I visualize JSONL (newline-delimited JSON)?

<p>The tool is designed for single JSON values (objects or arrays). For JSONL, you would need to wrap the lines in an array (e.g., [line1, line2, ...]) or use the JSON Formatter tool, which can handle multi-line JSON.</p>

Does it support JSON with comments or trailing commas?

<p>The tool uses the standard JSON.parse() parser, which does not allow comments or trailing commas. If your input contains these, it will be treated as invalid JSON. Use the JSON Repair Tool first to fix the syntax, then visualize the repaired output.</p>

Can I view just the summary without the full response?

<p>The summary is always displayed above the full response in the styled HTML output. There is currently no option to hide the full response, but you can copy just the summary text from the output.</p>