Developer
JSON to TypeScript
Convert JSON strings to TypeScript interfaces.
Open toolResources
All Castov resources are gathered here – tools, guides, and reference material for working with time, timestamps and time zones.
All Tools
Developer
Diff Checker
Compare text or code line by line.
Open toolDeveloper
JSON Formatter & Validator
Format, validate, minify, and sort JSON keys in your browser.
Open toolDeveloper
Base64 Encode / Decode
Encode and decode Base64 with UTF-8 Unicode and URL-safe support.
Open toolDeveloper
JWT Decoder
Decode and inspect JSON Web Tokens (JWT) header and payload locally.
Open toolDeveloper
UUID Generator
Generate cryptographically secure UUID v4 and v7 identifiers in bulk.
Open toolDeveloper
Hash Generator
Generate SHA-256, SHA-512, SHA-1, and MD5 hashes for text and files.
Open toolLabs
Service Worker API Mocker
Generate local fetch interceptor scripts to mock API endpoints.
Open toolLabs
P2P Ghost Tunnel
Share localhost via direct P2P WebRTC connection.
Open toolLabs
Steganography Env Vault
Hide encrypted .env files inside PNG image pixels.
Open toolLabs
Holographic JSON Explorer
Explore massive JSON architectures in a 3D WebGL universe.
Open toolLabs
Genetic Regex Auto-Healer
Evolve perfect Regex using local genetic algorithms.
Open toolLabs
Chrono-Debug API Replay
Replay past API states using a visual timeline scrubber.
Open toolLabs
AST Conflict Telepathy
Semantically merge Git conflicts using AST logic parsing.
Open toolLabs
NexusGrid
Decentralized WebGPU Supercomputer running local AI workloads.
Open toolLabs
Sonic-Gap Bridge
Air-gapped ultrasonic acoustic data transfer protocol.
Open toolLabs
Quantum Simulator
Browser-native quantum circuit execution via matrix tensors.
Open toolDeveloper
Gigantic JSON Viewer
Parse and view gigantic JSON files locally.
Open toolTimestamp
Unix Timestamp Converter
Turn a Unix timestamp into UTC, local time and ISO 8601.
Open toolTimestamp
Epoch Converter
See epoch seconds and milliseconds side by side, with UTC and local time.
Open toolTimestamp
Timestamp to Date
Readable date, weekday, day of year and ISO week from a timestamp.
Open toolTimestamp
Date to Timestamp
Convert a date, time and time zone into a Unix timestamp.
Open toolTimestamp
Current Unix Timestamp
Live Unix time in seconds and milliseconds. Copy, pause or refresh.
Open toolTimestamp
Milliseconds to Date
Convert Unix milliseconds, such as Date.now() values, to a date.
Open toolDeveloper
ISO 8601 to Unix
Turn an ISO 8601 date-time string into a Unix timestamp.
Open toolDeveloper
Unix to ISO 8601
Get an ISO 8601 string in UTC or with your local offset.
Open toolTime Zones
Timezone Converter
Convert time between zones and compare cities side by side.
Open toolDate & Duration
Timestamp Difference
Find the time between two timestamps as a duration.
Open toolTime Zones
UTC Converter
Convert between local time and UTC in any time zone.
Open toolDate & Duration
Date Difference Calculator
Years, months, weeks and days between two dates, leap years included.
Open toolDate & Duration
Time Duration Calculator
Elapsed time between two clock times, midnight crossings included.
Open toolDate & Duration
Add Time Calculator
Add seconds, minutes, hours, days or weeks to a date and time.
Open toolDate & Duration
Subtract Time Calculator
Subtract seconds, minutes, hours, days or weeks from a date and time.
Open toolDeveloper
Unix Timestamp Validator
Check whether a value is a valid Unix timestamp, with a clear reason if not.
Open toolTimestamp
Epoch Milliseconds Converter
Epoch milliseconds to a readable date, in UTC, local time and ISO 8601.
Open toolDeveloper
Unix Timestamp Batch Converter
Convert a whole list of Unix timestamps at once, with CSV export.
Open toolDeveloper
Date Format Converter
One date in, every common format out: ISO 8601, RFC 2822, RFC 3339, Unix and more.
Open toolDeveloper
ISO 8601 Converter
ISO 8601 to Unix time and back, in one combined tool.
Open toolDeveloper
RFC 3339 Converter
RFC 3339 to Unix time and back, the strict internet date-time format.
Open toolTime Zones
Time Zone Offset Calculator
Compare the UTC offset of two time zones and the gap between them.
Open toolTime Zones
World Clock
Live local time in several cities at once, with day and night shown.
Open toolTime Zones
Business Hours Converter
Compare working hours across time zones and find the overlap for meetings.
Open toolDeveloper
Cron Expression Generator
Build a cron expression and see a plain-English explanation of its schedule.
Open toolTime Zones
Timezone Travel Simulator
Visual timeline for debugging global events across regions.
Open toolDeveloper
Universal Config Sync
Real-time sync between JSON, YAML, and TOML.
Open toolDeveloper
Zero-Knowledge .env Vault
End-to-End encrypted .env sharing.
Open toolDeveloper
Universal Secret Scanner
Find leaked secrets in code before committing.
Open toolDeveloper
Shadow API Load Tester
Real-time API stress testing and latency charts.
Open toolDeveloper
Docker Architecture Visualizer
Generate diagrams from docker-compose.yml.
Open toolDeveloper
In-Browser SQLite Fiddle
Run SQLite entirely in your browser via WASM.
Open toolDeveloper
Code to Image Generator
Convert code snippets into beautiful images with gradients.
Open toolDeveloper
CSS Glassmorphism Generator
Generate frosted glass UI styles in CSS & Tailwind.
Open toolDeveloper
GitHub README Builder
Build dynamic GitHub profile READMEs with badges and live stats.
Open toolDeveloper
App & Screenshot Mockup Studio
Turn screenshots into 3D framed device mockups for Mac and iPhone.
Open toolDeveloper
Favicon & App Icon Generator
Generate multi-size favicon packages and HTML head tags.
Open toolDeveloper
Color Code Converter & Palette Studio
Convert colors between HEX, RGB, HSL, and Tailwind CSS tokens.
Open toolDeveloper
LLM Token & Cost Visualizer
Visualize BPE tokens and calculate real-time LLM API costs.
Open toolDeveloper
Git Disaster Recovery & Time-Traveler
Rescue lost commits, undo hard resets, and escape Git merge disasters.
Open toolDeveloper
SVG Keyframe Animator & Studio
Turn static SVG icons into animated CSS & Framer Motion vectors.
Open toolDeveloper
Synthetic Mock Data Studio
Generate realistic synthetic datasets in JSON, TypeScript, and SQL.
Open toolDeveloper
CyberChef & Magic Decoder
Auto-detect and decode Base64, JWT, Hex, ciphers, and hash pipelines.
Open toolAll Guides
- Running Local LLMs with WebGPURunning Large Language Models locally is the next frontier of AI. By leveraging WebGPU, developers can run models like Llama 3 entirely in the browser, eliminating server costs and ensuring absolute data privacy.6 min read →
- Understanding MCP ProtocolThe Model Context Protocol (MCP) is an open standard that allows developers to securely expose local resources, databases, and APIs to AI assistants. Learn how it turns isolated LLMs into context-aware agents.5 min read →
- Optimizing .cursorrulesAI code editors like Cursor are only as smart as the context they are given. A well-crafted .cursorrules file instructs the AI on your exact tech stack, architecture rules, and formatting preferences.4 min read →
- The Zero-Server AI EraDevelopers and teams are cautious about pasting proprietary code into external models. Zero-Server AI solves this by bringing the model directly to the user's device, ensuring that sensitive data is processed 100% locally.5 min read →
- Advanced Prompt PatternsPrompt engineering has evolved into a rigid software discipline. Master the architectural patterns of prompting to yield deterministic, high-quality code from unpredictable LLMs.7 min read →
- Understanding Regex ASTRegular Expressions are notoriously hard to read. By breaking them down into an Abstract Syntax Tree (AST), developers can easily debug, understand, and optimize complex patterns.4 min read →
- Mastering Docker ComposeDocker Compose allows developers to define and run multi-container Docker applications. Understanding the network topology and service dependencies is critical for modern infrastructure.5 min read →
- What Is Unix Time?A plain-language explanation of Unix time, the epoch and why programs count time this way.4 min read →
- Seconds vs Milliseconds TimestampsHow to recognise the unit of a timestamp, which platforms use which, and how to convert safely.4 min read →
- ISO 8601 Date and Time FormatHow ISO 8601 strings are built, what Z and offsets mean, and the parsing traps that cause off-by-hours bugs.5 min read →
- Time Zones and DST for DevelopersThe handful of rules that prevent most time zone bugs, with the daylight saving edge cases explained.5 min read →
- The Year 2038 ProblemWhy 32-bit Unix timestamps run out in 2038, what breaks, and how to check your own systems.3 min read →
- UTC vs GMT: What Is the Difference?Why UTC and GMT usually show the same time, how they differ technically, and which one to use in software.3 min read →
- Cron Expressions ExplainedHow the five fields of a standard cron expression work, with common patterns and the rule that trips people up.4 min read →
- Linux File Permissions & Chmod GuideHow Linux file permissions work, why octal numbers like 755 and 644 are calculated, and why chmod 777 is a dangerous anti-pattern.6 min read →
- JSON Web Tokens (JWT) Security Best PracticesHow JSON Web Tokens work under the hood, how to properly handle exp/iat expiration claims, and critical vulnerabilities to avoid in production.5 min read →
- Unix Timestamps in Python, JavaScript, and GoHow to generate and format Unix timestamps across JavaScript, Python, and Go, plus common pitfalls like milliseconds vs seconds.5 min read →
- Understanding Diff Algorithms and Patch WorkflowsThe math and mechanics of calculating text differences: Longest Common Subsequences, Myers algorithm, and unified diff syntax.5 min read →