He built an entire editable PowerPoint — slides, charts, live collaboration — into one HTML file
Bento is a single .html file that opens, edits, and syncs like a full presentation app: a readable JSON block holding the slide data, a compressed app shell underneath, and real-time multi-user editing routed through Cloudflare, all with no server-side app to host.
Bento packs a full PowerPoint-equivalent — slide editing, live viewing, embedded data, real-time collaboration — into a single HTML file you can open in any browser, no install, no account, no server-rendered app.
The creator showed up in the thread to explain the internals: readable JSON slide data up top, a compressed app shell that inflates in-browser, and end-to-end encrypted collaboration running through Cloudflare Durable Objects.
One pointed question in the thread: why does the homepage mention AI over twenty times, wrapped in walls of obfuscated base64 — a fair complaint about marketing noise on a genuinely clever piece of engineering.
One file, no server, a whole presentation app
Bento is a Show HN entry that landed with 747 points: a self-contained presentation tool where the entire application — editor, viewer, data model, and collaboration layer — lives inside a single .html file. Open it in any browser and you get a working PowerPoint-equivalent; no install, no account creation, no backend to stand up. It's part of a small but growing genre commenters call "single-file web apps" — software that behaves like a real app but ships and travels as one portable, inspectable document.
How it actually works, from the person who built it
The creator, posting under the handle starfallg, explained the architecture directly in the thread: the file is split into two parts. Near the top sits a plain, readable block of JSON holding the slide data itself — something you can grep, diff, or point automated tooling at without touching a binary format. Below that is the application shell, packed as a base64 blob that inflates in the browser at runtime using the DecompressionStream API, avoiding any external file fetches. Editing and viewing were built on reveal.js as a base, with GSAP/Flip handling animation — though the creator ended up reimplementing the original charting library (echarts) after running into size and behavior issues integrating it into the single-file model.
The collaboration piece is the most technically interesting: real-time multi-user editing runs through a small relay hosted on Cloudflare Durable Objects that only ever sees encrypted data from clients — the relay itself can't read what's being edited. Collaboration is off by default and switched on per-document by generating and sharing an invite file, with granular access control down to read-only users and the ability to revoke live-editing access per person. File System Access API handles writing edits back into the same .html file on disk, falling back to a plain download in browsers that don't support it, with every write cryptographically signed via ECDSA.
The complaint that landed anyway
Not every reaction was pure engineering enthusiasm. One commenter pushed back sharply on the marketing surface: "Why does the homepage mention AI over 20 times? Why does it mention AI at all? Why is most of it absurdly long and obfuscated base 64, which looks be binary data?" It's a fair criticism distinct from the technical merit of the tool itself — a landing page stuffed with AI buzzwords, sitting on top of genuinely novel single-file architecture, reads as marketing overreach layered onto real engineering, and several replies agreed the AI framing added noise rather than clarity about what the tool actually does.
That friction aside, the reception leaned strongly positive on substance. "This is awesome. I do love this software is one file thing," wrote one commenter, calling it "a breath of fresh air on these you-rent-everything-owns-nothing days" — a reaction to Bento's most distinctive property: there's no subscription, no vendor lock-in, and no server dependency standing between the user and their own presentation file. Another Show HN entry surfaced in the same thread — an unrelated infrastructure-automation project also named "bento" — a coincidence the creator noted with a shrug rather than a rebrand.
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