Usage

Everything on this page happens in the client after it is connected. The browser extension has the full set of entry points; the mobile apps and the web app have the launcher, sessions, files, and the dashboard but no context menu or download interception, because those hooks only exist in a browser extension. The web app has its own entry points instead.

The launcherCopy Anchor Link

The toolbar icon opens the launcher. Its tabs:

• Launch New lists the applications you may use, filtered by what you are opening: only apps that declare URL support appear for a link, only apps registered for the file's extension appear for a file. A search box narrows long lists.
• Active Sessions shows your running sessions with Re-open, Stop, and Send File (drop a file into a running session's Desktop/files).
• Manage Files opens the file manager.
• Upload to Storage appears when you arrived with a file and would rather keep it than open it: it goes straight into a home directory.
• Upload Files opens a page where you can drag a local file in and continue to the launcher with it.

Selecting an application reveals the launch options it supports:

The client also sends your browser's time zone, so clocks inside the session match yours.

Launch asks the server to start the container, waits until it answers (up to a minute, longer on the first pull of an image), then opens the session in a new tab. Sessions are streamed by Selkies: the tab is a full desktop application with clipboard, audio, file transfer, gamepads, and the rest, depending on what the template enables.

The right-click menuCopy Anchor Link

The extension adds a SealSkin group to the context menu:

Each of these opens the launcher with the context already filled in, or launches immediately if you pinned a behaviour for it.

Files are uploaded to the server in chunks over the encrypted API. Large files therefore take as long as your upstream bandwidth allows; the launcher shows the progress.

Intercepting downloadsCopy Anchor Link

Send Next Download to SealSkin puts a … badge on the toolbar icon and watches for one minute. The next download the browser starts is cancelled before it is written to disk, and the launcher opens with that file's URL so the server fetches it into a session instead. This needs the Chrome downloads API and is not available in Firefox or on mobile.

SessionsCopy Anchor Link

A session is one or more containers started for you, reachable through the server's session proxy at https://<server>:8443/<session id>/. The launch returns a one-time URL carrying an access token; opening it sets a cookie scoped to that session path and every later request is checked by the proxy against it. Nobody without the cookie reaches the container, and the container itself is never exposed.

Inside a session, proot-apps install <name> and the graphical installer (proot-apps install gui) add applications to the home directory. When your administrator assigned you a PRoot Apps catalog, both offer the catalog's apps and install from it, so the session reaches no registry; otherwise they fetch from the public repository as the image ships.

Sessions survive a server restart: they are recorded on disk and reattached on start-up, and records whose containers are gone are discarded. Stopping a session removes its containers and deletes any cleanroom storage. Sessions have no idle timeout of their own; administrators can stop anyone's session from the dashboard.

StorageCopy Anchor Link

Persistent data lives under /storage/<username>/ on the server:

• Home directories are folders you (or an administrator) create. One is mounted as /config inside the container, which is where LinuxServer.io images keep the application's profile and settings. Auto storage uses a home directory named after the app.
• Shared files (_sealskin_shared_files) is one folder per user that is mounted at /config/Desktop/files in every persistent session, whichever home directory is in use. Files you upload, intercept, or send to a session land here, so every application sees the same files.
• Cleanroom sessions get throwaway versions of both, deleted when the session stops.

Administrators can disable persistent storage per user or group, in which case every session is a cleanroom.

The file managerCopy Anchor Link

Manage Files in the launcher, or Files in the options page, opens a file manager over your home directories and shared files. It can:

• browse and search, with paging for large directories,
• upload files and whole folders, by button or by dropping them on the page,
• create folders and delete files (deletion runs in the background and reports when it is done),
• download a file (in Chrome the extension streams it chunk by chunk through the encrypted API; on mobile it is saved to the app and opened with the system viewer),
• open a file in an application: the launcher opens with the server-side file as its context and the app gets it without another upload,
• share a file publicly, if your account allows it.

A public share copies the file into public storage and returns a URL of the form https://<server>:8443/public/<share id> that anyone can open. A share can carry a password (stored as a salted scrypt hash) and an expiry in hours; expired shares are removed by a background job. Public Shares in the file manager lists yours with their URLs and lets you revoke them.

Collaboration roomsCopy Anchor Link

Launching with Collaborative Session opens the app in a room at https://<server>:8443/room/<session id> instead of a bare session. You are the controller. The room page wraps the streamed application with:

• Invite links for two kinds of guest: participants, who can be given input, and read-only viewers. Guests need no SealSkin account; the link carries a token, and each guest receives a personal token on first visit.
• Chat, with display names guests choose for themselves.
• Voice and video between everyone in the room, with a designated speaker the controller can set.
• Gamepad slots: the controller drags the container's gamepad slots onto participants, and their local controllers are forwarded into the session. A participant given several slots plays one with each of their controllers, in the order the browser lists them: the first takes the lowest-numbered slot. Dragging a slot back to the gamepad box frees that slot alone.
• Mouse and keyboard hand-over: the controller can give one participant the mouse and keyboard, and take them back.
• Application switching: the controller can open another installed app inside the same room. Each app gets its own container that shares the session's storage, and the room switches between them; apps can be stopped or restarted individually.

Under the hood the room's WebSocket relays chat and control messages, and the server pushes the current token table (who is controller, who holds which slots, who has the mouse and keyboard) into every container of the session. Stopping the session ends the room for everyone.

On mobileCopy Anchor Link

The iOS and Android apps host the same launcher, file manager, and dashboard. Differences from the extension:

• No context menus and no download interception. Share a file into the launcher with Upload Files instead.
• Sessions open in the system browser (a Chrome Custom Tab or Safari view), not inside the app, because the streaming client needs a real browser engine.
• Downloads from the file manager are written to the app's storage and opened with whatever the system offers for that file type.
• A trusted TLS certificate is mandatory; the WebView refuses self-signed certificates and mixed content.

In a browser, with nothing installedCopy Anchor Link

https://<server>:8443/ is the web app: the same launcher, file manager, and dashboard in an ordinary tab. It has no configuration file and keeps no key. Sign in with what the administrator set up: Sign In with OpenID Connect or Sign In with SAML takes you to your organization's identity provider and back, a reverse proxy that signs you in opens the app signed in, and the built-in administrator admin uses the root key at /#root. The dashboard shows who you are signed in as and has Sign out; a logout at the identity provider ends the sign-in as well.

The web app fills the window. A rail on the left (a tab bar at the bottom of a phone) moves between Home, Files, and the dashboard, and shows who is signed in. Your avatar opens your profile: how you are signed in and until when, the groups you are in and the ones your identity provider or proxy named, what your settings let you do, your limits with what is used of them, and the pools and catalog open to you, with Sign out at its foot. Home has a box that filters the applications as you type and takes a pasted link to open in isolation, the sessions you have running as cards that show their desktops, captured when you come to the page and refreshed now and then while you use it, with Open and Stop, and the applications as tiles, grouped by kind with your recent ones first. Opening a session in the same tab grows its card over the page into the desktop. A tile opens its application's launch options in a window that unfolds from the tile; the options are remembered per application, and the play button in the tile's corner launches with them straight away. Drop a file anywhere on the page to open it in an application that takes it.

The page is yours to arrange. From the options panel an application can be starred as a favorite or hidden from the page. Favorites sit in a row of their own above the applications, in the order you drag them into (or move them from the panel), and hidden applications wait under the Hidden chip until shown again. The brush beside the search box sets the page's background: a color, from the presets or your own, painted solid or as one of several gradients, or a picture of your own, filled, fitted, stretched, or centered, with blur and dim to taste. The sidebar folds away from the chevron at its foot and comes back from the tab left at the window's edge. All of this is kept in the browser, so each browser has its own arrangement.

Launching shows what the server is doing on the application's tile and in the sessions row: choosing a node, preparing storage, downloading the application the first time a node runs it, starting it, and waiting for its desktop. The session then takes the web app's place in the tab; the browser's back button is the way back. Open in a new tab, among the launch options, opens a tab at the click instead, which shows the same progress and becomes the session when it is ready, or says why it could not start.

Copy link, beside Launch, copies the application's address with the options chosen: /app/<application id>/, with the storage, the room, and the rest in its query. Opening the address signs you in if need be and takes you to your oldest running session of the application with that storage, room or not, or launches one. Bookmark it, or install it from the browser's menu as an app of its own, one per application; a session's own page offers the same install, for the session's options.

Where the administrator turned session isolation on, a session has an address of its own (<session id>.<session domain>) and opens in a tab of its own. If the launcher then says the server has no such name the browser reaches, the administrator has to give it wildcard DNS and a certificate for it.

On a cluster the launcher has a Where choice: leave it on Automatic, or pick a pool or a node. Each home directory shows the node that holds it, and a session using it starts there. Where the administrator allows, Move storage moves a home directory to another node once no session is using it. A line under the launcher shows what is left of a time allowance.

In place of the context menu:

• The bookmarklets. The dashboard's SealSkin in This Browser card has two links to drag to your bookmarks bar. Send to SealSkin opens the page you are on in SealSkin, or searches for the text you selected. Pick for SealSkin waits for your next click: click a link to open that link in SealSkin, or an image, video, or audio to send the file; Shift-click a link to send the file it leads to. A picked file is fetched by the page you are on, with your sign-in on that site, so it works for files only that site can read; anything the page cannot fetch opens as a link instead.
• web+sealskin: links. After Open web+sealskin: Links Here (Chrome, Edge, Firefox), a link such as web+sealskin:https://example.com opens its address in SealSkin.
• Search. The web app offers itself to the browser as a search engine (OpenSearch), and …/?q=terms and …/?url=address open the launcher with that search or address.
• As an installed app (Chrome and Edge, from the browser's install option): SealSkin becomes a target that other applications share links, text, and files to, and on a desktop it is offered to open the file types your installed applications open.

Sessions open in tabs of their own. While the web app's tab stays open, Re-open brings a session's tab forward and Stop closes it; after the web app is reloaded, and always in Safari, which lets the web app keep no hold on the tab, Re-open opens the session in a new tab. Where the web app cannot close the tab (Safari, and Chrome for a session at an address of its own), the tab closes itself a few seconds after Stop, when its page reconnects to the stopped session, or says the session stopped where the browser does not let a page close its tab.

Each session opens at an address of its own (see Session origins), which keeps its pages away from the web app and from other sessions altogether: session tabs get no link back to the web app, it cannot be framed, and nothing a session's page does can use your sign-in.

The options pageCopy Anchor Link

The extension's options page (and the dashboard of the app and the web app) is where the client configuration lives, alongside the account-level views: Configuration (connection, export your config file for another device, log out), Home Directories, Active Sessions, and Pinned Behavior. A connection made with an application key exports a file that carries the key, which another device imports on its connection page. Administrators see the management panels described in Administration in the same place.