Dev tools that just work.
JSON & Data
JSON Formatter & Validator
Format, beautify, minify, and validate JSON
JSON Converter
Convert JSON to CSV, XML, YAML, SQL, and more
JSON Schema Validator
Validate JSON against a JSON Schema
JSON Diff
Compare two JSON objects and find differences
CSV Viewer
Upload and view CSV files as interactive tables
Data to Excel
Convert JSON, CSV, or XML to downloadable Excel files
XML Formatter & Viewer
Format, beautify, minify, and validate XML
Text Tools
Regex Tester
Test and debug regular expressions in real-time
Word & Character Counter
Count words, characters, sentences, and paragraphs
HTML Formatter & Viewer
Format, beautify, minify HTML and preview live output
HTML to Markdown Converter
Convert HTML to clean Markdown with live preview
SQL Formatter & Beautifier
Format and beautify SQL queries with dialect support
List Parser
Parse, count, sort, filter, and reformat lists of IDs or values
About DevToolKit — Your Free Developer Toolbox
DevToolKit is a free suite of 19 browser-based developer tools that process data entirely client-side — your data never leaves your browser. Built for web developers, backend engineers, and DevOps professionals who need fast, reliable utilities without signup or data privacy concerns. Every tool works offline after the initial page load and runs in all modern browsers including Chrome, Firefox, Safari, and Edge.
Our JSON tools cover the complete JSON workflow: format and validate JSON with syntax highlighting and error detection, convert JSON to CSV, XML, YAML, or SQL, compare two JSON objects to find differences, and validate JSON against a schema with Draft 07 and 2020-12 support. For spreadsheet workflows, the CSV viewer renders CSV data as sortable, searchable tables, while Data to Excel converts JSON, CSV, or XML to downloadable .xlsx files.
Encoding and security tools include a Base64 encoder/decoder supporting text and URL-safe encoding (per RFC 4648), an image-to-Base64 converter for embedding images in HTML and CSS, a JWT decoder and encoder with color-coded token sections and signature verification (per RFC 7519), and a hash generator supporting MD5, SHA-1, SHA-256, and SHA-512 algorithms with HMAC support.
Generator and text tools round out the toolkit: the UUID generator creates v1, v4, and v7 UUIDs with bulk generation up to 1,000, the fake data generator builds realistic test datasets with a visual schema builder and exports to JSON, CSV, SQL, and XML. The regex tester provides real-time pattern matching with capture group display and a common patterns library, and the word and character counter analyzes text with reading time estimates and keyword frequency. New additions include the HTML formatter and viewer with live preview, an HTML to Markdown converter, an XML formatter with validation, a SQL formatter supporting MySQL, PostgreSQL, SQLite, and more, and a list parser that splits, counts, deduplicates, sorts, filters, and reformats raw ID lists into JSON, CSV, SQL IN clauses, XML, or YAML.
Unlike many online developer tools, DevToolKit processes all data 100% client-side using JavaScript. No data is uploaded to any server, no account is required, and all tools work offline after the initial page load. This privacy-first approach ensures sensitive data like API keys, JWT tokens, and production JSON never leaves your browser. According to the Stack Overflow Developer Survey, JSON is the most common data format used in modern REST APIs, making reliable JSON tools essential for every developer's workflow.
DevToolKit is also a Progressive Web App — you can cache all tools for offline use with a single click. Hit the Offline button in the navbar and every tool becomes available without an internet connection. You can even install DevToolKit as an app on your desktop or phone for a native-like experience. Learn more about our features.