Free private developer utilities
Format, encode, decode, preview and generate developer data instantly β 100% in your browser. No uploads, no signup, completely private.
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JSON Formatter
Format and validate JSON with a tree view, error line/column, key sorting and JSON5 support.
Base64 Encode/Decode
Encode and decode Base64, base64url and data URIs, including files.
URL Encode/Decode
Encode or decode URL components with instant validation.
JWT Decoder
Decode JWTs, check expiry and verify HS, RS, ES and EdDSA signatures locally.
Hash Generator
MD5, SHA-1, SHA-256, SHA-512, SHA-3, CRC32 and HMAC for text or files.
UUID Generator
Generate UUID v4, v7, v1 and v5 in bulk, and validate or decode any UUID.
Lorem Ipsum Generator
Create placeholder words, sentences or paragraphs for mockups.
Case Converter
Convert text to upper, lower, title, camel, snake, kebab and sentence case.
Timestamp Converter
Convert epoch s/ms/Β΅s/ns to dates in any time zone, with ISO 8601 and RFC 2822.
Regex Tester
Test JavaScript regex live with named groups, a match table and replace preview.
Markdown Preview
Preview Markdown as HTML locally using marked.
HTML Viewer
Online HTML editor with live preview for HTML, CSS and JavaScript, in a private sandbox.
HTML Beautifier
Beautify or compact HTML, CSS and JavaScript snippets in your browser.
CSV β JSON
Convert CSV to JSON and JSON back to CSV.
Number Base Converter
Convert numbers between binary, octal, decimal, hex and any base.
YAML β JSON
Convert YAML to JSON and JSON back to YAML locally.
XML Formatter
Format XML and convert XML to JSON in your browser.
SQL Formatter
Beautify SQL queries for common dialects locally.
HTML to Markdown
Convert HTML fragments to Markdown and download .md files.
JSON Diff
Compare two JSON objects and highlight recursive changes.
HTML Entities
Encode and decode named or numeric HTML entities.
Mock Data Generator
Generate seeded fake data as JSON, NDJSON, CSV or SQL INSERT statements.
Cron Explainer
Explain cron in plain English and list next runs; supports seconds, Quartz and @macros.
HTTP Status Codes
Search all HTTP status codes with RFCs, plus nginx and Cloudflare codes.
MIME Types
Look up about 150 file extensions and MIME types in both directions.
Cubic Bezier Editor
Edit CSS cubic-bezier easing curves visually.
CSS Unit Converter
Convert px, rem, em and pt with configurable base sizes.
ULID Generator
Generate sortable ULIDs individually or in bulk.
JSON to TypeScript
Infer TypeScript interfaces from a JSON sample in your browser.
JSON Schema Generator
Generate a draft-07 JSON Schema from a JSON sample.
.env β JSON
Convert a .env file to JSON and JSON back to .env locally.
cURL to Code
Convert curl to fetch, axios, Python, Go, PHP and C# β or fetch back to curl.
Emoji Picker
Search a categorized emoji grid and click to copy.
ASCII Table
Search the full ASCII reference with dec, hex, oct and char.
String Escaper
Escape or unescape JSON, JavaScript, HTML, URL and backslash sequences.
JSON to YAML
Convert JSON to YAML and YAML back to JSON using js-yaml.
Code Formatter (Prettier)
Format JS, TS, CSS, SCSS, HTML, JSON, GraphQL, Markdown and YAML with Prettier in your browser.
JavaScript Minifier
Minify JavaScript with Terser: compress, mangle and compare sizes locally.
CSS Minifier
Minify and restructure CSS with CSSO and see how many bytes you saved.
HTML Minifier
Minify HTML with inline CSS and JS, strip comments and whitespace, and compare sizes.
SVG Optimizer
Optimize SVG files with SVGO, preview before and after, and download the result.
SQLite Viewer
Open .sqlite and .db files, browse tables and run SQL queries locally.
JSON Viewer
Explore large JSON files as a collapsible tree, search keys and values and copy any node's path.
JSON to C#
Generate C# classes from JSON with System.Text.Json or Newtonsoft attributes.
JSON to Go
Convert JSON to Go structs with json tags, omitempty and unmarshal helpers.
JSON to Python
Generate Python dataclasses or Pydantic models with type hints from JSON.
JSON to Java
Generate Java POJO classes from JSON with Jackson annotations or Lombok.
JSON to Kotlin
Generate Kotlin data classes from JSON for kotlinx.serialization, Jackson or Klaxon.
JSON to Rust
Generate Rust structs with serde Serialize and Deserialize derives from JSON.
JSON to Swift
Generate Swift Codable structs or classes with CodingKeys from JSON.
JSON to C++
Generate C++ structs or classes with nlohmann/json to_json and from_json from JSON.
JSON to Zod
Generate Zod schemas and inferred TypeScript types from a JSON sample.
XML to JSON
Convert XML to JSON with attributes, repeated elements as arrays and typed numbers.
JSON to XML
Convert JSON to well-formed XML with attributes, a root element and indentation.
XML to YAML
Convert XML documents to readable YAML with attributes and nested lists.
TOON to JSON
Decode TOON (Token-Oriented Object Notation) back to formatted JSON with strict validation.
TOON to YAML
Convert TOON (Token-Oriented Object Notation) LLM output to readable YAML.
TOON to XML
Convert TOON (Token-Oriented Object Notation) data to well-formed XML.
TOON to CSV
Turn TOON tabular arrays into CSV for Excel or Google Sheets.
CSV to XML
Convert CSV or TSV to well-formed XML with custom root and row elements and typed values.
CSV to TOON
Convert CSV spreadsheets to compact TOON (Token-Oriented Object Notation) for LLM prompts.
CSV to YAML
Convert CSV rows to a YAML list of objects with numbers, booleans and nested keys.
Private developer utilities for everyday work
Dev Tools is a collection of practical browser-based utilities for formatting JSON, encoding Base64, decoding JWTs, generating hashes, testing regular expressions and previewing Markdown. Every tool runs locally with client-side JavaScript, so your snippets, tokens and sample data are never uploaded or stored on a server.
Choose a tool above to clean up an API response, convert text for a URL, generate UUIDs for test fixtures, inspect timestamps or beautify HTML, CSS and JavaScript. The goal is simple: fast, free developer helpers that respect privacy and work without accounts, queues or round trips.