Single-file apps that run entirely in your browser. No server, no cloud — data stays in your browser's localStorage. Some of these applications use online libraries for functionality. These libraries don't get your data!
Because web browsers have become so powerful, I now prefer to create applications that run in the local web browser. They do not connect to a server or a cloud service. Instead of using an online database, they store your data in the localStorage database of your own web browser. This way, they maintain some persistence and respect our privacy.
Download these applications (simply download the webpage) at your discretion, and use them as they are.
You may report bugs but I cannot promise that I will fix them quickly. I usually fix them when I also add new features.
I built this software for myself and with the help of AI. You may use them for free, but know that the best software is still written by real human programmers. If these tools do not quite suit you, look further for professional open source or commercial software.
Because I made these little tools for myself, the manual is generated with Claude Sonnet 4.6.
| App | Description | Technologies | Built with |
|---|---|---|---|
| SQLite Tool | A full-featured SQLite database explorer — pretty much everything you can do with a SQLite database, right in your browser. 📖 |
Claude Code (Fable 5)
Abacus AI Agent
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| My Private Writer | A private, in-browser split-screen Markdown editor: write Markdown on the left, see a live preview on the right. Multi-document tabs, line numbers, syntax-highlighted code, Mermaid diagrams, sanitized rendering, and export to Markdown, HTML, PDF, or plain text. Autosaves locally; nothing leaves your device. 📖 |
Claude Opus 4.8
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| Regex Companion | Learn to understand and write regular expressions interactively. 📖 |
Claude Code 4.6
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| Study Load Planner | Discover whether your study workload is too heavy. 📖 |
Claude Code 4.8
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| HTML Editor | Manually build HTML web pages the old-fashioned way. 📖 |
Grok 4.3
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| Markdown → HTML | Write Markdown and render it as HTML. 📖 |
Grok 4.3
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| Simple Markdown Viewer | An even simpler Markdown renderer for quick previews. 📖 |
Grok 4.3
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| PrivatePDF | Manage your own PDFs locally — merge, split, protect, reorder/remove pages, and redact sensitive text. 📖 |
Claude Sonnet 4.6
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| Text Diff | Quickly find how (and optionally using RegEx) two text files differ from each other. 📖 |
Claude Sonnet 4.6
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| CSV/TSV Viewer | Open TSV/CSV files, manipulate data, do Regex search & replace on columns, and save as SQLite or Excel. 📖 |
Claude Sonnet 4.6
Abacus AI Agent
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| ICO Editor (Iconic V1) | Edit or create ICO icon files, optionally from PNG or EXE files. 📖 |
Claude Sonnet 4.6
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| Iconic V2 | Edit or create ICO icon files, for power users — layers, selections, symmetry, dithering and SVG/ICO/PNG export. 📖 | Canvas API File API Drag & Drop API localStorage SVG import/export Vanilla JS No external libs | Claude Cowork (Fable 5) |
| Markdown File Manager | Create and edit Markdown files, export as HTML. 📖 |
Grok 4.3
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| Visionary Diagram Editor | Draw flowcharts, mind maps, and node-edge diagrams — with undo/redo, grid options, and dark/light/high-contrast themes. Everything stays in your browser. 📖 |
Claude Sonnet 4.6 reviewed by Claude Code (Fable 5)
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| Screenshot Annotator | Annotate screenshots and images with shapes, text, and freehand drawing — paste, drop, capture or load from URL. Includes local OCR for text extraction. Nothing leaves your browser. 📖 |
Claude Sonnet 4.6
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| JSON/YAML/XML Swiss Army Knife | Parse, edit, convert, query, diff, and encode JSON, YAML, and XML — pretty-print, tree view, JSONPath/XPath queries, schema validation, semantic diff, and format conversion to CSV, INI, and Markdown tables. 📖 |
Claude Sonnet 4.6
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| Audio Trimmer & Converter | Trim any audio file to an exact region, adjust volume and playback speed, apply karaoke voice reduction, and export as WAV, MP3, OGG, or WebM — all offline. 📖 |
Claude Sonnet 4.6
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| IBC — Image Batch Converter | Convert hundreds of images in bulk to JPEG, PNG, WebP, BMP, TIFF, or GIF — with six resize modes, flexible renaming, and ZIP or folder output. No upload, no cloud. 📖 |
Claude Sonnet 4.6
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| My Local Translator | In-browser neural translation of text and documents (.txt, .md, .pdf, .docx) using lightweight Opus-MT models — pick a direction, nothing is uploaded. 📖 |
Claude Opus 4.8
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| DocSeek | Search inside your own documents by meaning, not just keywords — load a PDF, DOCX, HTML, Markdown or text file and find the right passage even when you don't know the exact wording. Includes an exact/regex cross-check and an extractive overview. A small AI model runs entirely in your browser; nothing is uploaded. 📖 |
Claude Cowork (Opus 4.8)
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| Offline Transcriber | Drop in an audio or video file and get a timestamped transcript plus SRT/VTT subtitles, generated entirely in your browser with Whisper. Supports English, Dutch, German, French and auto-detect. 📖 |
Claude Sonnet 4.6
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Technologies: 🟦 JS/general | 🟧 WebAssembly | 🟪 External library | 🟩 Browser API | 🟥 Storage | Built with: 🟠 Claude | 🔵 Grok | 🟢 Abacus AI Agent
Note: only the apps where you don't spot a purple tag should still work when you're not connected to the internet. But even those with a purple tag won't upload your data to a server; they do download a library from a server when loading the page.