The Developer Toolkit Built for Speed
Format JSON, design ERDs, test REST APIs, decode JWTs, validate YAML — all inside your browser. No servers, no signup, no limits. Just tools that work.
JSON Formatter
Pretty-print, validate, and explore JSON data
Privacy First. Always.
Every tool runs 100% client-side via WebAssembly and browser APIs. Your data physically never touches a server — not even ours.
Instant Access. No Account Needed.
Open any tool and start working immediately. No signup forms, no API keys, no onboarding, no friction.
Unlimited Processing. Your Device.
Process gigabytes of JSON, validate massive YAML files, test complex regex — no rate limits, no paywalls, no caps.
Engineered for professional-grade workflows
LangStop is not another API wrapper or server-side tool aggregator. Every tool is a self-contained client-side application compiled to WebAssembly or built on native browser APIs. Open a tab, do the work, close the tab.
- Native-performance tooling. Every formatter, encoder, and validator runs on WebAssembly or native browser APIs — no server round-trips, no network latency.
- PWA offline support. Install as a Progressive Web App and every tool works without an internet connection. No network, no problem.
- Keyboard-first navigation. Every tool supports keyboard shortcuts and command palette access. Stay in flow without reaching for your mouse.
JSON Tools
Formatter, validator, diff, tree viewer, to code
API Client
REST client, WebSocket tester, status code reference
Security
JWT decoder/encoder, hash generator, password checker
Conversion
Base64, YAML, XML, TOML, timestamp, color converter
Database
ER diagram generator, SQL formatter, schema designer
Dev Utilities
Regex tester, cron helper, UUID, URL encoder, HTML entities
Your Daily Developer Toolkit
Fast, focused tools for the tasks you handle every single day.
ER Diagram Generator
Transform database schemas into beautiful, interactive Entity Relationship Diagrams.
AI Prompt Generator
Craft perfect prompts for ChatGPT, Claude, and other LLMs with built-in templates.
JSON to Code
Convert JSON into TypeScript interfaces, Go structs, Python classes, and more.
Real workflows, real speed
Professional tasks that most online tools struggle with — LangStop handles instantly.
Format 10MB JSON files in milliseconds
Large-file JSON formatting and validation that doesn't freeze your browser. WebAssembly-powered parsing handles files most online formatters choke on.
Design ERDs without leaving your browser
Entity-relationship diagrams from your database schema. Drag, zoom, export — all rendered client-side with zero server round-trips.
Test REST APIs with a native client
Full-featured HTTP client with syntax highlighting, response inspection, and history. No account, no installation, no data leaving your machine.
Convert between any format instantly
JSON → YAML → XML → TOML → CSV. Bidirectional conversion with schema preservation. All running on WebAssembly for near-instant results.
Frequently Asked Questions
Is my data really private?
Can I use these tools offline?
Are there usage limits?
Do I need to sign up or create an account?
How is this different from other online tool sites?
Can I contribute or request a tool?
Your Browser. Your Data. Zero Compromises.
Professional developers trust LangStop because it respects what matters most: their data stays private, their time is never wasted, and their workflow is never interrupted.