44 free developer tools that run entirely in your browser.
devtoolkit.mingrammer.com
No sign-up, no uploads, nothing leaves your machine: every converter, generator, and reference works offline once the page has loaded. Available in English and Korean, with light and dark themes.
- Find anything fast: press ⌘K / Ctrl+K anywhere to open the command palette. Search matches names, descriptions, and aliases in both languages (
b64,epoch,정규식), and recently used tools stay one click away. - Eight focused categories: Data Format, Encoding & Hashing, Generators, Web, Code, Text, Time & Date, and System & Network, ordered by how often each is needed.
- Fast by default: each tool is code-split and loads on demand, so the shell stays small no matter how many tools are added.
- Private by design: JWTs, secrets, images, and pasted data are processed with Web APIs in the browser and never sent anywhere.
44 tools across eight categories. Every link opens the tool directly.
| Tool | What it does |
|---|---|
| JSON Formatter/Validator | Format, validate, and beautify JSON with syntax error detection |
| JSON to CSV Converter | Transform JSON data into CSV format for spreadsheets |
| CSV to JSON Converter | Convert CSV data into structured JSON objects |
| YAML to JSON Converter | Transform YAML configuration files to JSON |
| JSON to YAML Converter | Convert JSON into human-readable YAML format |
| XML ↔ JSON Converter | Convert XML documents to JSON and back, attributes included |
| TOML ↔ JSON Converter | Convert pyproject/Cargo-style TOML to JSON and back |
| CSV to YAML Converter | Transform tabular CSV data into YAML structure |
| YAML to CSV Converter | Convert YAML data into CSV for data analysis |
| Locale Converter | Convert between language codes (ISO 639) and country codes (ISO 3166) |
| Number Formatter | Format numbers with currency, percentage, and thousands separators |
| Tool | What it does |
|---|---|
| Base64 Converter | Encode and decode Base64 strings with toggle modes |
| Image ↔ Base64 | Turn images into data URLs for inline HTML/CSS, or decode Base64 back to an image |
| Hash Generator | Generate MD5, SHA1, SHA256, SHA512, and other hash types |
| HMAC Generator | Keyed SHA-1/256/384/512 signatures for webhooks and API signing |
| Number Converter | Convert numbers between binary, decimal, hexadecimal, and octal |
| Tool | What it does |
|---|---|
| UUID Generator | Generate secure UUIDs (v4, v5) with namespace support |
| Password Generator | Create strong, secure passwords with customizable options |
| Lorem Ipsum Generator | Create placeholder text in words, sentences, or paragraphs |
| QR Code Generator | Create QR codes for text, URLs, and other data with customizable sizes |
| Tool | What it does |
|---|---|
| JWT Decoder | Decode header and payload, check expiry, verify HS256/384/512 signatures |
| URL Parser | Break a URL into parts and edit query parameters in a table |
| Color Converter | HEX, RGB, HSL, HSB, CMYK, tints/shades, and a WCAG contrast checker |
| HTTP Status Codes | Searchable reference for every response code with MDN links |
| MIME Types | Look up MIME types by extension or content type |
| Tool | What it does |
|---|---|
| JSON to Types | Generate TypeScript, Go, Kotlin, Python, or Rust types from JSON |
| SQL Formatter | Dialect-aware SQL beautifier and minifier |
| curl to Code | Convert curl commands into fetch, axios, requests, Go, PHP, or Ruby |
| Regex Tester | Test regular expressions with real-time matching and highlighting |
| Markdown Viewer | Preview markdown with syntax highlighting for code blocks |
| Tool | What it does |
|---|---|
| Case Converter | Transform text between camelCase, snake_case, UPPERCASE, lowercase, and more |
| Text Diff | Compare two texts and highlight differences side by side |
| Line Tools | Sort, dedupe, trim, number, prefix, join and split lines |
| Escape/Unescape Tool | Encode and decode HTML, URL, and JSON strings |
| Text to Slug | Convert text into SEO-friendly URL slugs |
| Word Counter | Count words, characters, sentences, paragraphs, and estimate reading time |
| Unicode Inspector | Code points, UTF-8 bytes, hidden-character detection and normalization |
| Tool | What it does |
|---|---|
| Unix Timestamp Converter | Convert between Unix timestamps and human-readable dates |
| Timezone Converter | Convert times between different timezones |
| Date Calculator | Days between dates, add/subtract time, ISO 8601 durations |
| Cron Generator | Create and validate cron expressions with human-readable descriptions |
| Tool | What it does |
|---|---|
| CIDR Calculator | Calculate network ranges, subnets, and IP address information |
| Chmod Calculator | Unix permissions in octal and symbolic form with presets |
| Byte Converter | Bits, bytes, KB/MB/GB vs KiB/MiB/GiB, and transfer-time estimates |
- Pick a tool from the home page, the sidebar, or the ⌘K command palette
- Enter your data in the input fields
- See instant results in the output area
- Copy results or download files as needed
Built with Vite, React 18, TypeScript, Tailwind CSS, and shadcn/ui.
git clone https://github.com/mingrammer/devtoolkit.git
cd devtoolkit
npm install # or: bun install
npm run dev # http://localhost:8080Other scripts: npm run build (production bundle in dist/), npm run preview (serve the build), npm run lint.
- Create the component in
src/components/tools/<Name>.tsx(default export, no props). - Add its strings to
src/utils/translations/<id>.tswith<id>_titleand<id>_descriptionin bothenandko, and register the module insrc/utils/translations/index.ts. - Register the tool in
src/utils/toolsConfig.ts(category, icon, search aliases) and its lazy import insrc/pages/ToolPage.tsx. - Add an SEO entry under
src/utils/seo/, a URL inpublic/sitemap.xml, and a line in this README.
The command palette, sidebar, home grid, and related-tools chips pick it up automatically.
Pushing to main runs the Deploy to GitHub Pages workflow, which installs dependencies with npm ci, builds, and publishes dist/ to devtoolkit.mingrammer.com. There is no server: the site is static and routed with hash URLs, so it can also be hosted on any static file host.
Contributions are welcome! Feel free to:
- Report bugs
- Suggest new tools
- Submit pull requests
- Improve documentation
This project is open source and available under the MIT License.