Online JSON Viewer & Pretty-Print Formatter
Inspect, validate, pretty-print, and search large JSON, GeoJSON, and HAR payloads locally in your browser without sending API data to third-party servers.
Drag & drop files here, or click to browse
Open single or multiple files simultaneously in tabs
🔒 Your files stay on your device. We never upload your files to any server.
Why Developers Need a 100% Client-Side JSON Viewer & Formatter
JavaScript Object Notation (JSON), standardized by RFC 8259 and ECMA-404, is the foundational data interchange format of modern web APIs, cloud configuration files, NoSQL document databases, GeoJSON spatial maps, and HTTP Archive (.har) network captures. Because production systems often serialize JSON in minified single-line strings to reduce bandwidth, inspecting a raw 5 MB .json payload in a basic text editor is slow and unreadable.
Countless developers paste production API responses or upload .json and .har files to online "JSON beautifiers" without realizing those websites log payloads on backend servers or expose sensitive bearer tokens, session cookies, customer PII, and internal microservice URLs. HTTP Archive (.har) files in particular contain full Authorization headers and session secrets that should never be uploaded to an external site.
FilePeek processes .json, .geojson, and .har files strictly inside your browser sandbox. When you open a JSON file, FilePeek validates its syntax, provides one-click Pretty-Print (2-space indentation) and Minify toggles, applies clear syntax highlighting to keys, strings, numbers, booleans, and nulls, and lets you search or copy the formatted payload with zero network transmission.
Technical Specifications
Architectural details and file format parameters verified by FilePeek.
| Standards | RFC 8259 / ECMA-404 JSON Data Interchange Format |
|---|---|
| Supported Extensions | .json, .geojson, .har |
| Maximum File Size | 500 MB Local In-Memory Processing |
| Formatting Modes | Pretty-Print (Indented), Minified, Raw Source |
| Syntax Validation | Native JSON.parse verification with error line reporting |
| Secret Protection | Zero server logging — safe for HAR & API payloads |
How to Open & View JSON Viewer Files
Step-by-step instructions for viewing files without installing desktop software.
Drop Your .JSON, .GEOJSON, or .HAR File
Drag your JSON file onto the dropzone above or click "Browse Files" to load it from your local filesystem.
Automatic Syntax Check & Highlighting
FilePeek validates whether the JSON structure is well-formed and renders color-coded syntax highlighting with line numbers.
Pretty-Print, Wrap Lines & Search Keys
Click "Format / Pretty-Print" to expand minified single-line JSON into a readable hierarchy, toggle word wrap, and search for specific keys.
Copy Formatted Output or Inspect Info
Copy the formatted JSON to your clipboard with one click or inspect file size and encoding details in the File Information panel.
JSON Viewer Viewer Features
Modern browser utilities designed for clarity, performance, and privacy.
One-Click JSON Pretty-Print & Minify
Transform single-line minified API dumps into cleanly indented 2-space JSON hierarchies—or compact them back—instantly.
Real-Time JSON Syntax Validation
Detects trailing commas, unquoted keys, or truncated payloads and displays the exact syntax error message from the parser.
Color-Coded Syntax Highlighting
Distinguishes object keys, string values, numeric literals, booleans, and nulls with high-contrast WCAG AA accessible colors.
Safe HAR & API Token Inspection
Inspect Chrome/Firefox .har network captures and production JSON logs safely without leaking Authorization headers to the cloud.
Line Numbers, Word Wrap & Fast Search
Navigate deeply nested objects with numbered lines, optional line wrapping, and instant keyword search.
One-Click Copy to Clipboard
Copy either the raw or pretty-printed JSON payload directly to your system clipboard for use in Postman, IDE, or docs.
Common Real-World Scenarios
How professionals and casual users rely on FilePeek's local engine daily.
Debug large REST/GraphQL JSON responses, MongoDB/DynamoDB exports, and webhook payloads without exposing production data.
Open customer-submitted .har network diagnostic files safely in the browser to inspect failed API requests and status codes.
Inspect .geojson feature collections, coordinate arrays, and property attributes before loading them into mapping tools.
JSON Viewer Frequently Asked Questions
Answers to common questions regarding JSON Viewer rendering and privacy.
Is it safe to open production JSON or HAR files containing API keys in FilePeek?
Yes. Unlike online JSON beautifiers that send your text to a backend server, FilePeek runs 100% locally in your browser. Your tokens, cookies, and customer data never leave your device.
Can FilePeek format a minified single-line JSON file?
Yes! Click the "Pretty-Print" button in the viewer toolbar to automatically parse and indent minified JSON with clean 2-space formatting.
What happens if my JSON file has a syntax error?
FilePeek still displays the raw text with line numbers so you can see the file contents, and shows a clear validation banner explaining where the JSON syntax error occurred.
How large of a JSON file can I open?
FilePeek supports JSON files up to 500 MB, and uses smart rendering safeguards on massive files to prevent browser tab freezes.
Does it also support GeoJSON and HAR files?
Yes, both .geojson and .har files are native JSON structures and are fully supported with syntax highlighting and pretty-printing.
Related File Viewers
Explore other zero-installation format viewers available on FilePeek.