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Castov
100% Client-Side•Zero-Data Logging•Works 100% Offline

The Complete Developer Toolkit
Web + CLI + AI (MCP)

All your mission-critical utilities executed locally in your browser, terminal, and AI agents. Zero server tracking, sub-millisecond transforms, and seamless multi-stage pipelines.

Smart Omnibox:Ctrl + K
Terminal CLI:npx castov
Cursor & Claude:castov mcp
Explore 61 Tools MCP Server (13 Tools)CLI Guide
castov-playground ~ zsh
Try:
Castov DevShell v0.2.0 (Zero-Latency Browser Sandbox)

Simulates the full castov-cli suite locally via WebCrypto and instant transforms.

Click any quick-run chip above or type help to see commands.

castov$
Offline-first•0ms Latency•WebCrypto E2EE
Ready for CI/CD & TerminalCLI Docs
Built for Speed, Privacy & AI

Why Developers Choose Castov

Five architectural decisions that make Castov the preferred toolkit for modern software teams.

Zero-Data Logging

WebCrypto

100% of cryptography, JWT inspection, JSON formatting, and timestamp parsing executes in local browser memory. Not a single keystroke is sent to external servers.

Tool Pipelines ("Pipe to...")

Chaining

Pass outputs seamlessly across utilities in one click: JSON directly to TypeScript interfaces, Cron schedules into world timezones, and diffs to schema generators without clipboard juggling.

Unified Ecosystem

Web • CLI • MCP

The exact same 13 utilities work on the Web, in your local terminal via castov, and inside Cursor or Claude via our Grade-A certified Model Context Protocol server.

Encrypted URL Shares

Zero-Server

Share inputs, diffs, and settings with teammates instantly. Payloads are compressed into the URL hash fragment (#) so servers never see what you shared.

E2EE Cloud Sync & Team Vaults

GitHub OAuth

Zero-friction leverage unlocked on registration

Connect Workspace

Connect your GitHub account to sync pinned utilities, presets, and dev preferences across all your machines. Collaborate with teammates using RSA-OAEP encrypted Team Vaults to share .env files without cleartext exposure in chat channels.

GLOBAL DISTRIBUTION & MCP ECOSYSTEM

Deploy Castov Everywhere You Build

Whether inside your local terminal, Docker containers, AI editors, or automated CI/CD pipelines — Castov provides the instant execution layer for developers and MCP AI agents.

Official Container Verified Distribution

Docker Hub

Run Castov CLI and MCP runtime in an isolated, non-root Alpine container with zero host dependencies.

Official Registry
terminal execution
docker run --rm -it castovdev/castov:latest --help
Lightweight Alpine runtime (~50MB footprint)
Strict non-root user execution (USER node)
Direct MCP transport streaming via stdin/stdout

Advanced Capabilities

We didn't just build formatters. We built the architecture required by modern engineering teams.

P2P Multiplayer Canvas

A visual node-editor for building data pipelines. Connects peers in real-time using WebRTC and CRDTs (Yjs) with direct peer-to-peer data channels coordinated through public signaling servers (which may receive connection metadata). Workflow graphs, node configurations, and payload data are never stored on Castov servers.

Steganography Environment Vaults

End-to-end encrypted environment variables. We hide your secure AES keys inside standard image pixels (Steganography) for invisible sharing, entirely in your browser.

API Mocker (Service Worker)
Intercepting
GET /api/v1/users
{ "status": 200, "data": [ { "id": "usr_91x", "role": "admin" } ] }

Test your frontend without a backend. Our Local API Mocker runs entirely in your browser's Service Worker to simulate payloads globally.

Explore Our Toolkit

From time manipulation to cryptography, everything is beautifully structured and instantly accessible.

Timestamp

7 tools

Convert, validate, compare and work with Unix timestamps.

Date & Duration

5 tools

Calculate differences, durations, and add or subtract time from a date.

Time Zones

6 tools

Convert, compare and browse time across the world's time zones.

Developer

33 tools

ISO 8601, RFC 3339, cron and other formats developers work with daily.

Labs

Experimental tools

Experimental tools: WebRTC P2P mesh, steganography, AST parsing, and in-browser WebGL computing.

10 experimental tools
Service Worker API MockerLab

Generate local fetch interceptor scripts to mock API endpoints.

Open experiment
P2P Ghost TunnelLab

Share localhost via direct P2P WebRTC connection.

Open experiment
Steganography Env VaultLab

Hide encrypted .env files inside PNG image pixels.

Open experiment
Holographic JSON ExplorerLab

Explore massive JSON architectures in a 3D WebGL universe.

Open experiment
Genetic Regex Auto-HealerLab

Evolve perfect Regex using local genetic algorithms.

Open experiment
Chrono-Debug API ReplayLab

Replay past API states using a visual timeline scrubber.

Open experiment
AST Conflict TelepathyLab

Semantically merge Git conflicts using AST logic parsing.

Open experiment
NexusGridLab

Decentralized WebGPU Supercomputer running local AI workloads.

Open experiment
Sonic-Gap BridgeLab

Air-gapped ultrasonic acoustic data transfer protocol.

Open experiment
Quantum SimulatorLab

Browser-native quantum circuit execution via matrix tensors.

Open experiment

Frequently Asked Questions

Everything you need to know about Castov.

Frequently Asked Questions

Is Castov really free?
Yes. All tools are free, with no account and no usage limits. The site may show ads in the future to cover running costs.
Is my data sent to a server?
Time, date and converter tools do not upload your input to Castov servers. Some preferences, such as theme, custom time zones and selected models, are stored locally on your device. Some features use the network by design: Env Vault uploads an encrypted copy, P2P Ghost Tunnel uses public STUN discovery with manual token exchange, and Developer Canvas connects to public WebRTC signaling servers (which may receive connection metadata; workflow graphs and payloads are never stored on Castov servers).
What is a Unix timestamp?
A Unix timestamp is the number of seconds since 1 January 1970 at 00:00:00 UTC. It identifies one moment in time regardless of time zone, which is why programs and APIs use it.
Should I use seconds or milliseconds?
Use whichever your system produces. A 10-digit value is in seconds and a 13-digit value is in milliseconds. The converters can detect the unit for you.
Which time zones are supported?
All IANA time zones supported by your browser, such as America/New_York, Europe/Paris, Africa/Algiers and Asia/Tokyo, with daylight saving time rules applied for the date you choose.

Ready to supercharge your workflow?

Free browser-based developer tools. Some collaboration, cloud, and external API features may require an account or additional configuration.

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