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PrivUtil

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PrivUtil mascot

PrivUtil is a privacy-first, offline-capable developer utility suite. Built with Go and React, it provides 65+ tools across 11 categories for data manipulation, formatting, conversion, generation, and more — all running locally with zero server tracking.


PrivUtil Screenshot

✨ Features

Data & Diff

Tool Description
Diff Utility Compare pasted text or uploaded files; readable text is diffed inline, binary files are compared by SHA-256 checksum
Text Tools Sort, dedupe, reverse, trim, inspect line count/word count/bytes
Text Similarity Levenshtein distance and similarity percentage
Spell & Grammar Checker Fully offline spelling and grammar/punctuation checking; English and Latin American Spanish; embedded ~50k-word dictionaries; inline wavy underlines with one-click fixes; add words to a persistent custom dictionary (never flagged again)
Token Counter Offline LLM token counter; exact BPE for OpenAI (o200k_base/cl100k_base), heuristic estimates for Claude/Llama 3/Gemini/Mistral, plus classic tokenizers; char/byte counts, token preview, side-by-side comparison

Formatters & Converters

Tool Description
JSON Formatter Format, minify, sort keys, validate
Universal Converter JSON ↔ YAML ↔ XML ↔ TOML ↔ CSV (bidirectional, configurable delimiter)
Data Validator Validate JSON, YAML, XML, TOML with line/column error reporting
SQL Formatter Beautify and format SQL queries
Color Converter HEX ↔ RGB ↔ HSL with live preview
Case Converter camelCase, snake_case, PascalCase, kebab-case, CONSTANT_CASE, Title Case
Time Converter Unix timestamps, timezone conversion, ISO 8601
Number Base Converter Decimal ↔ Hex ↔ Binary ↔ Octal ↔ Base64
IP Calculator IPv4/IPv6 subnet, network/broadcast/hosts
Markdown ↔ HTML Bidirectional conversion
HTML/MD Viewer Render HTML or Markdown in a sandboxed iframe with strict CSP, file upload (.html/.md), opt-in images

Generators

Tool Description
UUID Generator v1, v2, v3, v4, v5, v6, v7, v8; configurable hyphens, uppercase, count
Hash Calculator MD5, SHA-1, SHA-256, SHA-512, bcrypt (configurable cost)
Lorem Ipsum Words, sentences, paragraphs, configurable count
Password Generator Custom charset, length, uppercase/lowercase/digits/symbols, bulk generation
RSA Key Pair 1024/2048/4096-bit key generation

Encoding & Crypto

Tool Description
Base64 Encode text or uploaded files; decode raw or data-URI input with MIME-aware inline preview (text, images, PDF, audio, video, and binary/gRPC payloads as text up to 5 MB)
URL Encoder/Decoder Percent-encoding
HTML Entity Encoder/Decoder Named and numeric entities
HMAC Generator SHA-256/SHA-512/SHA-1/MD5 with hex and base64 output
OTP/TOTP Generate and validate RFC 6238 codes; generate secrets; configurable period/digits/algo
ULID Generator Monotonic option, bulk generation
Caesar Cipher / ROT13 Arbitrary shift, encode/decode
Text Encode Text ↔ binary, hex, octal, decimal codepoints
Morse Code Encode/decode with standard alphabet
Basic Auth Generator Encode/decode user:password as Authorization header

Developer Tools

Tool Description
JWT Debugger Decode header and payload; highlights expiration
Regex Tester Go-compatible regex, match highlighting, captured groups
JSON to Go Generate Go structs with json tags from any JSON
Cron Tools Explain cron expressions, next 5 run times
Certificate Parser Parse X.509 PEM certificates (subject, issuer, SANs, validity)
String Escape/Unescape JSON, Java, SQL, HTML entity modes

Network Tools

Tool Description
Subnet Calculator IPv4/IPv6 CIDR: network, broadcast, netmask, host range, count
chmod Calculator Interactive Unix permission calculator; octal ↔ symbolic ↔ checkboxes; setuid/setgid/sticky
IPv4 Converter Decimal ↔ dotted ↔ hex ↔ binary representations
IPv4 Range Expander Start+end → individual IPs + CIDR summary
Port Generator Random port(s), configurable range, exclude well-known
MAC Address Generator Random or OUI-specific, configurable separator, unicast/local bits

Text & String

Tool Description
Slugify URL-safe slug with separator, uppercase, max-length options
Hidden Character Detector Reveals zero-width spaces, BOM, non-breaking spaces; annotated/cleaned output
Find & Replace Plain text or regex, case-insensitive option, replacement count
String Obfuscator Partial masking, configurable keep-start/keep-end/mask-char
Numeronym Generator i18n, k8s, a11y style
NATO Alphabet Encode/decode text to/from NATO phonetic alphabet
List Tools Sort A-Z/Z-A/numeric, dedupe, shuffle, unique-only, duplicates, frequency, reverse, trim, remove-empty

Math & Units

Tool Description
Math Expression Evaluator Recursive-descent parser, 30+ functions (trig, log, factorial, gcd, lcm, clamp, lerp…), variables, degrees mode, configurable precision
Percentage Calculator 4 modes: X% of Y, X is what % of Y, % change, reverse percentage
Temperature Converter Celsius ↔ Fahrenheit ↔ Kelvin with formulas
Unit Converter 6 categories: bytes (SI+binary), length, mass, area, volume, speed

Date & Time

Tool Description
Date Difference Calendar-aware diff (years/months/days/hours/minutes/seconds + totals + human summary)
Leap Year Checker Single year, comma list, or YYYY-YYYY range
Date Add/Subtract Add/subtract years, months, weeks, days, hours, minutes, seconds
Date Formatter 20+ output formats: ISO 8601, RFC 2822/850, Unix (s/ms/µs/ns), ordinal, SQL, ISO week date…
Date Info Week number, quarter, zodiac sign, season, day-of-year, days-left, days-since-epoch

Web & DevOps

Tool Description
URL Parser Scheme, credentials, host, port, path, query params (table), fragment, normalized URL
User-Agent Parser Browser, version, OS, engine, device type (desktop/mobile/tablet/bot)
HTTP Status Codes Searchable reference of all 63 codes (1xx–5xx) with descriptions, filterable by category
MIME Type Lookup Bidirectional: extension → MIME or MIME → extensions; 75+ types; category filter
Docker run → Compose Full flag parser (30+ flags), quoted-string aware, generates docker-compose.yml with warnings for unsupported flags
Git Cheat Sheet 11 categories, 120+ commands, searchable, copy-on-click

Media Tools

Tool Description
SVG Optimizer 4 presets (safe/aggressive/minimal/custom), 9 configurable transforms, size stats, inline preview
Image Metadata (EXIF) JPEG full EXIF (camera/GPS/settings), PNG chunks (IHDR/tEXt/iTXt/pHYs), WebP RIFF; GPS decimal + DMS + Maps link
Base64 ↔ File Encode any file to base64/data URI; decode base64/data URI to downloadable file; image preview

🚀 Quick Start

Important

PrivUtil should NOT be installed via go install. This project uses an embedded web component that must be built separately. Standard go install fails to bundle these assets correctly, resulting in an incomplete application. Please use the pre-compiled binaries from the Releases page or build from source using the provided Makefile.

Docker

Check out the project packages here

docker pull ghcr.io/odinnordico/privutil:latest
docker run --rm -p 8090:8090 ghcr.io/odinnordico/privutil:latest

To keep the container running and auto-restart it if it ever exits, add a restart policy:

docker run -d --restart=unless-stopped -p 8090:8090 ghcr.io/odinnordico/privutil:latest

Running as a service (auto-restart)

To run PrivUtil under systemd with automatic restart on failure, use the provided unit at deploy/privutil.service:

sudo cp privutil /usr/local/bin/privutil
sudo cp deploy/privutil.service /etc/systemd/system/privutil.service
sudo systemctl daemon-reload
sudo systemctl enable --now privutil

The unit sets Restart=on-failure, so the process is relaunched within ~1s if it exits unexpectedly.

Download from Releases

Download the latest binary for your platform from the Releases page.

Linux / macOS

# Example for Linux AMD64
tar -xzf privutil-linux-amd64.tar.gz
./privutil

Windows

  1. Right-click the .zip file and select Extract All...
  2. Run privutil.exe

Build from Source

# Clone the repository
git clone https://github.com/odinnordico/privutil.git
cd privutil

# Build everything
make build

# Run
./privutil

Access at http://localhost:8090

CLI Options

./privutil --help

Options:
  -port string          Port to listen on (default "8090")
  -host string          Host to bind to (default "127.0.0.1"; use 0.0.0.0 for all interfaces)
  -allowed-hosts string Comma-separated extra Host header values to accept (for LAN/custom-domain access)
  -custom-dict string   Path to the spellchecker custom-dictionary file (default: <user-config-dir>/privutil/custom-dictionary.txt)
  -mcp                  Serve the in-process MCP endpoint at /mcp for local LLM agents (default true)
  -log-level string     Log level: debug or info (default "info")
  -version              Print version and exit

Environment variables: PORT, HOST, ALLOWED_HOSTS, CUSTOM_DICT, MCP, LOG_LEVEL

The server binds to loopback (127.0.0.1) by default and only accepts requests whose Host header is localhost/127.0.0.1/::1 (a DNS-rebinding defense). To expose it on a LAN, set -host 0.0.0.0 and add the reachable host name(s) to ALLOWED_HOSTS.

🤖 MCP Server (for AI agents)

PrivUtil exposes its tools to local LLM agents over the Model Context Protocol, served in-process by the same binary — no separate server or process is launched. It's a Streamable HTTP endpoint at /mcp, reachable at http://localhost:8090/mcp while PrivUtil is running.

Point your agent's CLI at that URL. For example, with Claude Code:

claude mcp add --transport http privutil http://localhost:8090/mcp

Or in a client config that takes MCP server definitions:

{
  "mcpServers": {
    "privutil": { "type": "http", "url": "http://localhost:8090/mcp" }
  }
}
  • No login — access is gated by the same loopback bind + Host-header allowlist as the rest of the server; cross-origin browsers are refused (no CORS, Origin check), and the endpoint is body-size- and rate-limited. Every tool handler is panic-recovered.
  • ~70 tools exposed (pure, offline, no side effects) spanning hashing/crypto, encoding, data & formats (JSON/YAML/XML/TOML/CSV, JSON→Go, SQL), text (diff, regex, case, tokens, spell-check, hidden chars), network (IP/subnet, URL, MIME, HTTP status), math/units/dates, generators (UUID/ULID/password/RSA/OTP), and dev utilities (cron, docker→compose, cert parse). Call tools/list for the full catalog.
  • Disable it with -mcp=false / MCP=false.

🛠️ Development

Prerequisites

  • Go 1.21+
  • Node.js 18+
  • Make

Makefile Commands

make build          # Build frontend + backend
make build-web      # Build React frontend only
make build-go       # Build Go binary only (requires web/dist to exist)
make run            # Build and run
make clean          # Clean build artifacts
make test           # Run all tests
make test-backend   # Go tests with coverage
make test-frontend  # Vitest tests
make test-coverage  # Generate HTML coverage reports
make lint           # Run all linters
make lint-backend   # go vet + go fmt
make lint-frontend  # ESLint
make proto          # Regenerate protobuf code

Project Structure

privutil/
├── cmd/privutil/       # Main application entry point
├── internal/
│   ├── api/            # gRPC service implementations (domain-grouped handlers)
│   └── server/         # HTTP/gRPC-Web server
├── proto/              # Protocol Buffer definitions and generated Go code
├── web/                # React frontend (Vite + Tailwind)
│   ├── src/components/ # UI tool components
│   ├── src/lib/        # Shared utilities and navigation
│   └── src/proto/      # Generated TypeScript proto bindings
└── Makefile

Request flow:

Browser (React + nice-grpc-web) → HTTP server (gRPC-Web wrapper) → gRPC handlers → Go business logic

🎨 Theme

PrivUtil features a Kawasaki Lime theme with dark/light mode toggle:

  • Primary Accent: #76FF03 (Neon Green)
  • Default Mode: Dark
  • Toggle in the top-right header

🧪 Testing

Backend (Go)

  • Coverage: 85%+ on core business logic
  • 150+ tests covering all gRPC handler methods
go test -tags=manual -cover ./...

Frontend (React/Vitest)

  • Dashboard, ThemeToggle, and component utilities coverage
cd web && npm test

🤝 Contributing

  1. Fork the repository
  2. Create a feature branch: git checkout -b feature/amazing
  3. Make changes and add tests
  4. Run linters: make lint
  5. Run tests: make test
  6. Commit using Conventional Commits: git commit -m "feat: Add amazing feature"
  7. Push and open a Pull Request

See CONTRIBUTING.md for detailed guidelines.

📄 License

MIT License — See LICENSE for details.

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PrivUtil is a privacy-first, offline-capable developer utility suite

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