Sidecar | A Classy Nostr Signer by The Daniel

Sidecar lives in your browser's side panel 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 and NIP-44 encrypt/decrypt, and your relay list.
Private keys are encrypted at rest (PBKDF2 to AES-GCM via WebCrypto), never stored in plaintext, never transmitted off your device.
PIN-protected with automatic re-lock, and a warning before signing anything that would wipe your follows, mutes, or profile.
Multiple accounts. Store as many keys as you like, switch the active one in a click, drag to reorder. Each site stays pinned to the account it logged in with, so there's no identity mix-up.
Per-site permissions with a prompt that previews exactly what you're signing. Relay sign-in (NIP-42) is answered for your own relays, for reading as well as posting, so relays that gate reads stop coming back empty.
Recent activity records what each signature actually was, and any row that signed an event opens it in your client, so the log can be checked rather than taken on trust.

📄 Backups that survive the browser

A printable backup sheet for a new key, styled as an old-fashioned telegram: the nsec as text you can copy and as a QR you can scan back in, plus a serial to tell sheets apart. A locked second page carries the key as a password-encrypted secret that passes for a masquerade invitation. Import by photo, PDF, clipboard image, or live camera scan. All generated locally, nothing uploaded.
One encrypted vault export covers accounts, wallets, and settings, and restore shows exactly what it will replace.

👤 Your profile, your way

View and edit your profile, with the bio editor opening as tall as your bio.
Edit and publish your outbox relays (NIP-65) right from your profile.
An account overview drawer: following count, relays, NIP-05, Lightning address, wallet status.
Follow-list recovery. If another app wipes or shrinks your follows, scan your relays and restore a healthy earlier version.
Check your relays: each one carries its own icon, and you can ask whether it is answering, gated behind payment or login, or holding none of your notes, which is the thing worth knowing before you drop it.
Your npub as a QR code, with your profile picture in the middle, so handing someone your key does not mean reading out sixty-three characters.

✍ Post without leaving the page

A composer for notes with @mention autocomplete across your follows and all of Nostr, embedded note previews, link cards, and image/video upload to your own Blossom servers.
Drafts autosave per account and are encrypted at rest. A short review countdown lets you read the note exactly as it will publish.
Post a poll instead of a note, and read the full tally in the panel when the votes come in.
Comment on any web page (NIP-22), and keep the bookmark lists your other clients write (NIP-51).

🔔 Notifications at a glance

A bell shows replies, mentions, reposts, reactions, and zaps for your active account, each opening in your preferred web client.
Reply to a note or a comment without leaving Sidecar. What you are answering stays on screen while you write, through the preview and the review countdown both.
Your circle comes first: replies from outside your follows, and their follows, are gathered into a counted group at the bottom rather than mixed in. Nothing is hidden and nothing is deleted.
Mute lists written by any client are respected, including muted words, hashtags, threads, and senders.

⚡ Lightning wallet (Nostr Wallet Connect)

Connect your own self-custody Lightning wallet over Nostr Wallet Connect. If you don't have one yet, built-in suggestions help you pick.
Send to an invoice or a Lightning address: a pasted invoice shows its amount, description and expiry before you pay, and an address resolves to the real recipient. Receive with a QR, view history, and back up or export your connection.
Pay a Lightning invoice from any page, including one the site copies to the clipboard, plus a WebLN provider with per-site spending budgets you can edit or revoke at any time. A payment of 10,000 sats or more always asks twice.
Automatic zaps, capped and only on sites you've actually signed into.
Podcasting 2.0 boosts, paid from your own wallet, with the show and the message named on the approval.
Balance in sats, BTC, or fiat, with a 24-hour price chart.

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

🎭 Sixteen themes

A gallery you can filter by dark or light, showing a live preview of each one before you choose it. Eight are drawn for low light and eight for daylight, each with its own display typeface, textures, and balance animation. A single switch turns the animations off.

🛡 Private by design

Open source. No analytics, no tracking, no remote code. Everything runs locally in your browser, and link previews are fetched with a guard against private-network requests.
Built for Firefox 128+ and also available for Chrome, Brave, Edge, and other Chromium browsers. Pin Sidecar, open the sidebar, and you're ready. 🍸

🗞 What’s new

1.15.2
• Open tabs stay connected when Sidecar updates or restarts. A client you keep open no longer fails with “Sidecar was updated” until you reload it.
• A warning before signing a follow list that suddenly grows by hundreds, which is how another account’s list looks. With more than one account, it names the account.

1.15.1: the expanded composer's text field is readable in every light theme, and its backgrounds are drawn at the panel's scale. Some themes received minor style refreshes. Refreshing the wallet no longer redraws the history.

1.15: four new themes, two dark and two light, and one of the originals in black and white. On this day. Send shows an invoice before paying it, and payments of 10,000 sats or more ask twice. Connected clients are told your own relays.

Prior releases include:
• alt text on images, a full-tab composer, CLINK offers, poll results.
• polls, proof of work on posts, name search ranked by your circle.
• reply from notifications, strangers sorted to the bottom of the bell, relay sign-in.
• the theme gallery, relay health checks, your npub as a QR.