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Capsule

Single-file web apps that save their data into SQLite

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Hey HN,I always had the problem that building HTML pages is really simple now, but trying to save data required hosting it somewhere, and sharing it afterwards was not easy. Over the last few months, I've been building an app called Capsule (it’s also the file extension name) written in Rust with Tauri 2.0 that allows packing an HTML app and its data into a single SQLite file.The HTML file and any related assets are directly embedded in the database. User data can either be saved as a localStorage key/value store or via a MongoDB-inspired collections API as documents, saved in a table in the file. You can also save other assets, like PDF files or images, directly in the database to keep different documents together. All data can be easily exported to CSV or JSON if needed.Privacy and security were a big priority for me, so documents cannot do anything out of the box. They don’t have direct access to the file system and they require permission to access the internet. The permission model is still something I’m working to improve. Capsule documents can also use local or remote AI models for document specific AI features.One downside with this approach is that multiple people working on it will create different copies. To make it possible to merge different copies of the same file, each data entry has a unique UUID and timestamp.I’m planning to open up the file format specification for the 1.0 version of the app so other apps can read or write Capsule files.You can try it out in the web preview at https://withcapsule.app/preview with pre-built templates or use any AI provider of your choice to create a custom, Capsule-optimized app by using the following prompt:"Please read the app wizard instructions at https://withcapsule.app/prompt.txt and help me design an app.“I’m still working on the file format but there are migrations for each new version, so data should never be lost when using newer versions of the app in the future. Please let me know if you have any ideas or use cases where this might make sense or does not work.

HN · launched Sep 15, 2026 · 377 upvotes (top 1%) · 1 view

Niche: software development frameworks · 154 launches, 4 in the last 7 days ▼ -76% · Explore this niche →

Category and tags

  • Horizontal
  • Dev tools
  • Developer
  • Not AI
  • Hobby / open-source project

Visit website ↗ Source listing ↗

Could you build this?

Partial A single-file document format running web apps backed by embedded SQLite across desktop and mobile requires a robust native runtime container, file virtualization, and custom bundling.

What it would actually take: The app is implemented in Rust with Tauri or a custom Wry/WebKit wrapper, bundling SQLite compiled to WebAssembly or linked natively with virtual VFS support inside a zip/tar archive format. The hard parts are cross-platform native packaging (macOS, Windows, Linux, Android) that handles arbitrary embedded web views safely and sandboxed read/write access to embedded databases. A developer needs strong systems programming in Rust and cross-platform desktop/mobile runtime experience.

Discussion

20 comments analyzed.

Competitors mentioned: Decker, Nash, PocketBase, Cordova/Phonegap

Concerns raised: Vendor lock-in with proprietary .capsule format, Security risks of distributing executable web apps/HTML files, iOS friction opening standalone HTML files with JavaScript, File corruption when stored in cloud sync folders like OneDrive

Feature requests: Open-source the app and spec, Merge UI for manual conflict resolution, Intelligent sync management for cloud folders

Competitors

Other products that read as similar to this one : 152 launches clear the similarity bar, closest 8 shown.

Attention rank: #2 of 153 (itself plus its competitors, highest first, normalized so YC and Product Hunt are compared fairly).

Launched 321 days after the earliest competitor.

  • Capsule · hn · 2026-07-07 · 5 upvotes · similarity 0.55
  • Moogo · ph · 2026-10-21 · 2 upvotes · similarity 0.41
  • SNKV · hn · 2026-02-24 · 36 upvotes · similarity 0.41
  • SnkvDB · hn · 2026-02-16 · 5 upvotes · similarity 0.41
  • UMedia · ph · 2026-09-30 · 2 upvotes · similarity 0.40
  • ChikkaDB · hn · 2025-11-29 · 5 upvotes · similarity 0.40
  • Eatmydata.ai · hn · 2026-06-10 · 8 upvotes · similarity 0.39
  • SQLite for Rivet Actors · hn · 2026-02-28 · 45 upvotes · similarity 0.39

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