Developer tools that just work
Format JSON, convert timestamps, encode Base64, generate UUIDs and more. Every tool runs 100% in your browser — your data never leaves your device.
All Tools
Fast, focused tools for everyday development workflows.
JSON Formatter
Format, filter and explore JSON in your browser.
SQL Formatter
Beautify and minify SQL in your browser.
YAML ↔ JSON Converter
Convert between YAML and JSON in both directions.
Timestamp Converter
Convert Unix timestamps and dates in both directions.
Base64 Encoder / Decoder
Encode or decode text, images, files and URL-safe Base64 — all in your browser.
URL Encoder / Decoder
Encode or decode URL components safely.
UUID Generator
Generate UUID v1, v3, v4, v5, NIL and Max identifiers, or parse an existing UUID to inspect its version, variant and v1 metadata.
Hash Generator
Compute MD5, SHA-1, SHA-256 and SHA-512 hashes.
Regex Tester
Test regular expressions with live highlighting.
JWT Decoder
Decode JWT header and payload without verification.
Color Converter
Convert colors between HEX, RGB and HSL.
Text Counter
Count characters, words and lines in real time.
Text Diff
Compare two texts line by line and spot changes at a glance.
HTTP Request
Send custom HTTP requests and copy them as cURL.
User-Agent Parser & Generator
Parse any User-Agent string to identify browser, OS, device and engine, or generate realistic User-Agents by platform or device brand.
DNS & IP Tools
DNS lookup, IP geolocation and IPv4/IPv6 conversion in one tool.
Cron Expression Tool
Parse, describe and predict cron expressions.
Mock Data Generator
Generate realistic mock test data: Chinese names, emails, phone numbers, ID cards, addresses, companies, bank cards, IPs, UUIDs and more. Export as CSV or JSON.
URL / UTM Parameter Parser
Parse URLs into protocol, host, path and query parameters. Highlight UTM and ad attribution params, find duplicates and empty values.
RSA / AES Encrypt & Decrypt
Encrypt and decrypt text with AES-GCM, AES-CBC or RSA-OAEP, and sign or verify with RSA-PSS. All powered by the Web Crypto API, 100% in your browser.
QR Code Generator
Generate QR codes from URLs or text. Choose size, error correction level and colors, then download as PNG or copy to the clipboard.
Password Generator
Generate strong or readable passwords with strength estimation.
Timezone Converter
Convert a time across multiple timezones and compare UTC offsets.
WebSocket Debugger
Connect to WebSocket servers, send and receive text or binary messages, and inspect connection status and close codes.
Markdown Preview
Write and preview Markdown in real time with a rich toolbar. Supports GFM, tables and task lists, and exports clean HTML or .md files.
JSON Schema Generator
Infer a JSON Schema (Draft-07) from a sample JSON object. Handles nested objects, arrays, required fields, enums and number ranges.
Whois Lookup
Query domain registration details through RDAP: registrar, registration and expiration dates, statuses, nameservers and abuse contact.
Image Converter
Convert and compress images between PNG, JPEG and WebP. Adjust quality, resize, convert to grayscale and rotate - all in your browser.
Document Converter
Convert between Markdown, HTML, CSV, JSON, XML and Office documents.
Why developers choose DevToolBox
DevToolBox is a lightweight toolbox for common development tasks. No accounts, no server round-trips, no data collection — open your browser and get things done.
100% client-side
All computation happens locally with JavaScript. Your JSON, text, tokens and request data are never uploaded to a server.
Privacy first
There is no backend, no database and no analytics tracking. Close the tab and your data is gone.
Fast & lightweight
Built with Next.js static generation and a system font stack, pages load fast and work well on mobile.
Developer friendly
Clean, focused interfaces with copy buttons, keyboard-friendly controls and clear error messages.
Tool categories
Formatting & Validation
Encoding & Decoding
Generators
Text Tools
Security & Encryption
Frequently Asked Questions
Everything you need to know about DevToolBox.
Are the tools really free?
Yes. Every tool in DevToolBox is completely free and does not require an account or a subscription.
Is my data sent to a server?
No. All tools are pure client-side applications. Your input is processed in your own browser and never transmitted to us.
Why do some HTTP requests fail with a CORS error?
Browsers enforce CORS to protect users. If a remote API does not allow browser requests, you will see a readable CORS hint. Use the Copy as cURL button and run the command in a terminal instead.
Can I use DevToolBox offline?
After the page is loaded, most tools continue to work without a network connection because all logic runs locally.