API payloads
Working with JSON responses
If you are working with API payloads, start with the JSON Formatter to pretty-print responses, the JSON Lint & Validator to verify syntax, or the JSON Lint tool to catch duplicate keys and trailing commas.
Developer · 11 tools
The utilities you reach for every day.
Browser-based utilities for JSON formatting, UUID generation, encoding, and more — running locally, with nothing leaving your device.
11 tools
0 installs
100% in-browser
// 11 tools
UUID Generator
Create RFC-compliant UUID values in your browser for development workflows
f47ac10b-58cc-4372-a567…
0192b4a0-9c3f-7e1a-b2d4…
0192b4a0-9c3f-7e1a-b2d4…
Base64 Encoder / Decoder
Encode text to Base64 or decode Base64 back to text in your browser, with URL-safe variant, MIME wrapping, and charset support
Hello, world!
SGVsbG8sIHdvcmxkIQ==
SGVsbG8sIHdvcmxkIQ==
URL Encoder / Decoder
Percent-encode or decode URLs and query strings in your browser with component and full-URL modes
hello world & more=1
hello%20world%20%26%20more%3D1
hello%20world%20%26%20more%3D1
HTML Entity Encoder / Decoder
Convert HTML special characters to entities and back in your browser, with named, decimal, and hex output and a sandboxed live preview
JSON Formatter
Pretty-print JSON with configurable indentation, in your browser
{"x":1,"y":"hi"}
{ "y": "hi" }
{ "y": "hi" }
JSON Minifier
Strip whitespace from JSON to produce compact output, in your browser
"name": "Ada", "id": 42
{"name":"Ada","id":42}
{"name":"Ada","id":42}
JSON Lint
Find duplicate keys, trailing commas, comments, and other issues
{"a":1,"a":2}
⚠ Duplicate key “a”
⚠ Duplicate key “a”
Regex Tester
Test regular expressions with flags
Unix Timestamp Converter
Convert Unix timestamps to dates in any timezone, and dates back to timestamps. Supports seconds, milliseconds, microseconds, and nanoseconds.
Cron Expression Parser
Paste a cron expression and instantly see what it means in plain English, plus when it will fire next — with timezone support and special-character handling.
JSON to CSV Converter
Convert a JSON array of objects into a downloadable CSV file — entirely in your browser. Supports nested objects, JSONLines, and a live preview before you download.
How to choose
Pick the right tool for your task
Encoding / Decoding
Query strings & headers
For encoding and decoding, the Base64 Encoder / Decoder and URL Encoder / Decoder handle the two most common encoding schemes in web development. Use them to debug query strings, decode headers, or prepare data for transport.
Identifiers & payload size
Test data & config files
Need a unique identifier? The UUID Generator produces spec-compliant v4 UUIDs. To trim payload size before shipping, the JSON Minifier strips whitespace from valid JSON.
About Developer Tools
Tool Matic's developer tools give you instant access to the utilities you reach for daily - JSON formatting, UUID generation, encoding, and more - without installing anything or leaving your browser.
Whether you're debugging an API response, generating test data, or decoding a Base64 payload, these tools are built to be fast, accurate, and zero-friction. Open a tool, paste your input, get your result.
Every tool in this category processes data entirely within your browser using JavaScript. Nothing is uploaded, stored, or logged.
What you get
- Instant results No server round-trips. Results appear as you type.
- Nothing leaves your browser Open DevTools → Network. Zero outbound data requests.
- Works without installing Open a tool, paste your input, get your result.
- Runs on your device Formatting, encoding and decoding happen in your browser, never on a server.
Frequently asked questions
Do these developer tools send my data anywhere?
No. Every developer tool on Tool Matic runs entirely in your browser using client-side JavaScript. Your inputs are never transmitted to a server — open any tool and start using it immediately.
Do I need an internet connection?
Only to open the page. Once it has loaded, all processing runs in your browser and nothing you enter is sent to a server. Reloading the page needs a connection.
Do you store the JSON or data I paste in?
No. All Tool Matic developer tools execute client-side using JavaScript in your browser. Your inputs are never transmitted to Tool Matic servers. You can verify this yourself by opening your browser's DevTools Network tab - you will see zero outbound requests carrying your data.
What is the difference between a JSON formatter and a JSON validator?
A JSON formatter takes valid JSON and re-indents it for readability - it assumes the input is already valid. A JSON validator checks whether the input conforms to the JSON specification and reports syntax errors. Use the JSON Formatter when you need readable output, and the JSON Lint & Validator when you need a strict spec check.
Is it safe to decode a JSON Web Token (JWT) online?
For inspection of decoded claims, browser-based JWT tools that run entirely client-side never send the token to a server. However, never paste a production token that you intend to reuse: any token that touches your clipboard or a third-party tool should be considered exposed. For production debugging, use short-lived tokens or revoke the token after inspection.