Sidecar | A Classy Nostr Signer Autor: The Daniel

Sidecar lives in your Firefox sidebar and hands every Nostr web app a secure window.nostr to sign in with — so you never paste your nsec into a website again. Your keys stay on your device, encrypted behind a PIN. It’s a companion to your favorite Nostr client, not a replacement: sign, post, and zap in a tap, then jump right back to the app you love.

🔑 Your keys, your control

Full NIP-07 signer: getPublicKey, signEvent, NIP-04 & NIP-44 encrypt/decrypt, and your relay list.
Private keys are encrypted at rest (PBKDF2 → AES-GCM via WebCrypto) — never stored in plaintext, never transmitted off your device.

PIN-protected (at least 8 characters, with a live strength check) and automatic re-lock, on by default after a period of inactivity you can adjust. A paste guard blocks dropping an nsec anywhere except the import field.

Multiple accounts — store as many keys as you like, switch the active one in a click, drag to reorder. Switching works the way you’d expect: log out of a site, switch accounts here, log back in, and the site follows — while sessions you’ve left open elsewhere keep signing as the account they started with.

Per-site permissions with a clear prompt that previews exactly what you’re signing — with human-readable event kinds and a heads-up on the few worth a second look. Relay auth (NIP-42) signs automatically so clients stay connected.

🔐 Key portability

Import or export any account as a NIP-49 ncryptsec — a password-encrypted key, so it never has to touch a clipboard as a raw nsec.
Back up or restore your whole vault — every account’s key and connected wallet — in one encrypted file.
NIP-05 identifiers are verified against their domain, with a check or warning right on your profile.

👤 Your profile, your way

View and edit your profile, see your following count, and publish updates in a tap.
Edit and publish your outbox relays (NIP-65) right from your profile.
Follow-list recovery — if another app wipes or shrinks your follows, scan your relays and restore a healthy earlier version (powered by Mutable).

✍ Post without leaving the page

A composer for notes with @mention autocomplete that searches your follows and all of Nostr, embedded note previews, link cards, and image/video upload (to your own Blossom servers, with an automatic fallback).
Drafts autosave per account, and a short review countdown lets you read the note exactly as it’ll publish before it sends.

🔔 Notifications at a glance

A bell shows replies, mentions, reposts, reactions, and zaps for your active account — opening instantly and updating live while you watch, and always reflecting a mute the moment you check (even one made in another app). Each taps through to your preferred web client.

⚡ Lightning wallet (Nostr Wallet Connect)

Connect any NWC wallet — Alby Hub, Zeus, YakiHonne, Coinos, Minibits and more — with built-in suggestions to help you pick one.

Send (BOLT11 or Lightning address), receive by invoice or by your Lightning address (with a QR), view history, and back up or export your connection (PIN-gated, with a QR).

Pay a Lightning invoice from any Nostr page in a tap, plus a WebLN provider with optional per-site spending budgets you can edit or revoke any time.

Sidecar never holds your funds — you stay in control of your own wallet.

🎨 Dressed to your taste

Three themes, switchable in Settings. Speakeasy — the original after-hours velvet — stays the default, joined by Film Noir, a matte black-on-black with silver accents, and Art Deco, a daylight eggshell-and-bronze palette with a geometric backdrop. Your choice sticks across sessions, and the “Pay with Sidecar” card injected on web pages wears the same look.

🛡 Private by design

Open source. No analytics, no tracking, no remote code — everything runs locally in your browser. Link previews are fetched with a guard against private-network requests.
Works in Firefox 128 and later (plus Chrome, Brave, Edge, and other Chromium browsers). Open the sidebar, and you’re ready. 🍸