openPowerTools
A zero-account browser toolbox. Everything stays on your device.

How it works

All your data is stored in a local SQLite database inside your browser. Nothing is sent to any server. There are no accounts, no profiles, no sign-ups. Open the page and start working.

Tools

Notes
Write quick text notes or organize ideas on a freeform sticky board with draggable, resizable, color-coded blocks.
Markdown Editor
Paste or drag-and-drop Markdown files for instant rendered preview. Save and version documents in the built-in library.
JSON Prettifier
Format and explore JSON with a collapsible, syntax-highlighted tree view. Expand, collapse, and copy with one click.
JSON Diff
Compare two JSON documents. View structural changes by path or use side-by-side inline diff with keyboard navigation.
To-Do Lists
Create multiple to-do lists with sections and tasks. Set due times with presets and get browser notifications when they are due.
Diagram Viewer
Render Mermaid and C4 architecture diagrams with hierarchy or force layout. Right-click any node for Context view to trace connections.
Sequence Diagram
Write UML sequence diagrams in sequencediagram.org syntax. Participants, activations, fragments, notes and refs render live as you type.
Drawing Board
Sketch with pen, draw shapes, pick colors and sizes. Export as PNG or copy-paste to Excalidraw. Save with version history.
Generators
Generate UUIDs (v4, v7), ULIDs, Nano IDs, passwords, API keys, and random tokens. All client-side with crypto-grade randomness.
Converters
Base64, URL, and HTML entity encoding. JWT decoder, hash generator, Unix timestamp converter, and color format converter (HEX/RGB/HSL).

Export / Import

Your entire workspace can be exported as a single .sqlite file and imported on another device or browser. Use the Export / Import buttons in the top-right corner of the tab bar.

Tips

Drag tabs to reorder them however you like. Your layout is saved between sessions.
Save & version documents in Markdown Editor, Diagram Viewer, and Drawing Board. Load any previous version from the library.
Drag & drop files onto most editors - JSON, Markdown, Mermaid diagrams, and more.
Use keyboard shortcuts: Ctrl+B toggle editor, Ctrl+Z undo, P/E/R/O/L/A for drawing tools.
Context view in Diagram Viewer: right-click any node to see all incoming and outgoing connections at a glance.
JSON Diff supports two modes: structural changes list and inline side-by-side. Use Prev/Next to jump between differences.
To-Do Lists can send browser notifications when a task is due. Click the Notifications badge to enable.
Drawing Board stores drawings in Excalidraw format. Copy to clipboard and paste directly into Excalidraw, or the other way around.
Each tool URL is bookmarkable: share /json-prettifier or /diagram links directly.