An encrypted pastebin. Text is encrypted in the browser before it is uploaded, and the decryption
key travels in the URL fragment — the part after #, which browsers never send to a server.
The practical consequence: whoever runs the server, including the person who wrote it, cannot read what users store. Not "does not", cannot. A full database dump contains ciphertext and nothing that would decrypt it.
- Zero-knowledge encryption. AES-256-GCM, key derived with HKDF from a random 32-byte seed that exists only in the share link.
- Optional password. Argon2id over the password is folded into the key, so both the link and the password are required. Neither alone is enough, and the server has neither.
- Expiry that actually deletes. 10 minutes to 3 months; 3 months is the default and the hard ceiling. There is no database — each paste is one opaque object, deleted by whichever comes first: the request that tried to read it, the 15-minute sweep, or (on Cloudflare) the R2 lifecycle rule. Self-hosted, the file's bytes are overwritten before it is unlinked. This design rejected Cloudflare D1 specifically because its Time Travel keeps deleted data restorable for weeks.
- Unguessable, unindexed links. 128-bit random ids,
X-Robots-Tag: noindex,Referrer-Policy: no-referrer, and a viewer whose server-rendered HTML contains no content at all. - Syntax highlighting and formatting for the languages listed in
src/lib/languages.ts— all of it in the browser, because the server has no plaintext to work with. - Markdown pastes open rendered, with the source one click away and a contents list in the
margin once there are three headings to navigate. Rendered by
react-markdown, which builds elements and never sets inner HTML: raw HTML in a paste is text and stays text. That is not fastidiousness — script running on the viewer page could read the decryption key out oflocation.hash, so the renderer has to be one that cannot be talked into running any. - Mermaid diagrams are drawn, from a
```mermaidfence, in whichever theme the reader is in — and replaced by the source, with the parser's complaint above it, when a diagram will not parse. Mermaid hands back a string of SVG; the string is parsed inertly and rebuilt as elements against an allowlist rather than set as inner HTML, so the property in the bullet above is kept rather than traded for a picture. The library is by some way the largest thing this app can pull in, and a paste with no diagram in it never fetches it. - A viewer that stays out of the way. Its controls — theme, folding, copy, and the Markdown source toggle — sit in one cluster that is invisible until you point at it.
- Node 22+ and pnpm (
corepack enable pnpm) - No database. Storage is Cloudflare R2 or a local directory, depending on where you deploy.
- HTTPS in production. Not a recommendation:
crypto.subtledoes not exist in an insecure context, so on plain HTTP outside localhost the app cannot encrypt anything.
corepack pnpm install
cp .env.example .env # set STORAGE_DIR to a local path, e.g. ./local-store
corepack pnpm devcorepack pnpm test # crypto, envelope, store, formatters, folding, theme
corepack pnpm test:e2e # Playwright against a production build
corepack pnpm typecheckSee docs/AGENT-DEPLOY.md. It is written as a runbook an AI agent can follow end to end — hand it to Claude Code or similar with shell access — and it works just as well read by a person. Two supported targets:
Cloudflare Workers + R2 (primary):
pnpm wrangler r2 bucket create zeropaste
pnpm cf:deployFits the Workers Free plan (~2.7 MiB of the 3 MiB worker limit; the heavy client bundles are free static assets). The runbook covers lifecycle rules, the WAF rate limit, and what Cloudflare can and cannot see.
Docker, self-hosted (strongest privacy posture):
cp .env.example .env
docker compose up -d --buildOne container, one volume, no database. Terminate TLS in front of it.
| File | Contents |
|---|---|
| docs/PLAN.md | Architecture, tech stack decisions, and the feature roadmap |
| docs/AGENT-DEPLOY.md | Deployment runbook, including failure modes |
Stated plainly, because a security tool that oversells itself is worse than none:
- A malicious or compromised server. It serves the JavaScript that does the encryption, so it could serve JavaScript that leaks the key instead. This is the inherent limit of browser-based encryption and applies to every product in this category. Self-hosting is the mitigation: the server is you.
- Anyone who has the link. The link is the key. Treat it like a password.
- Browser history, proxies that log URLs, and chat clients that preview links. The fragment is not sent over the network, but it is in the URL bar and in history.
- Access-pattern metadata, on the Cloudflare deployment. Cloudflare's edge sees each request's IP, paste id, and timestamp — never the content or the key, but "who fetched what, when" is visible to them. This worker ships with observability logging disabled to avoid adding our own copy of that record. If access patterns themselves are sensitive, self-host.