CEF As Service

Chromium as a service. Run real Chromium (CEF) browsers on a Windows server and stream them to any web browser. A Broker gives each client its own headless browser worker and relays video, audio and input over WebSocket or WebRTC. A small Admin web app manages it all.

 ┌──────────────┐   WebSocket / WebRTC    ┌──────────┐ WebSocket ┌─────────────────────┐
 │ Any browser  │ ◄─────────────────────► │  Broker  │ ◄───────► │ Worker (CEF, OSR)   │ × N
 │ (viewer page)│   video · audio · input │          │           │ one per session     │
 └──────────────┘                         └────▲─────┘           └─────────────────────┘
                                               │ loopback control channel
                                          ┌────┴─────┐
                                          │  Admin   │  settings · workers · encoders
                                          └──────────┘

Features

• One real Chromium per client. Each session runs in its own worker process and uses Chromium's own user agent.
• Two transports: WebSocket (JPG frames or encoded video) and WebRTC (video + Opus audio, TURN-ready).
• Multi-account isolation: by default, each tenant gets one persistent browser context. With --isolation-mode-session, every tab gets its own context, so you can run several logins to the same site side by side.
• Sessions that survive: configurable session timeout and manifest TTL, last-URL restore, and logins kept across Broker restarts.
• Full interaction: mouse, keyboard, touch and on-screen keyboard (Android), popups. Phones get a mobile viewer page automatically.
• Mobile device mode: Chrome DevTools' device list (iPhone, Pixel, Galaxy, iPad, foldables and more) with the device's user agent, Client Hints and touch, rotation and device zoom.
• Session recording: record a tab to MP4 (video) or MP3 (audio only) and download it when you stop. The recording feature only works on non-sensitive sites; otherwise, the recording is blocked.
• DevTools in the viewer: Chromium's own DevTools for each tab, in a resizable side panel (off by default, switched on in Admin).
• Drag and drop inside the page: with a drag preview that follows the pointer; a link dropped on the address bar or the sidebar opens it.
• Pluggable video encoders: loaded from plugins/encoders/. The OpenH264 plugin is included (the codec itself is a one-click download from Cisco, see below); the built-in formats are JPG.
• Admin web UI: password-protected and loopback-only. Start/stop/restart the Broker, view live workers (OS, client IP, created), and manage encoder settings, session timeout, default URL and executables.

How it fits together - processes, tenants, isolation modes, transports and connection modes, with diagrams: How CAS works.

Quick start (release build)

▶ Watch the setup video

1. Download the latest zip from Releases (CEF included) and extract it to a folder you can write to, e.g. C:\CefAsService (not C:\Program Files, see Running on Windows).
2. Run Admin\Xilium.CefGlue.Broker.Admin.exe.
3. Open http://localhost:57402, create the admin password and press Start.
4. Clients open https://<host>:57443/broker. On a LAN you'll see a one-time warning for the self-signed certificate.
5. For H.264 video (required for WebRTC): Admin → Encoder Settings → openh264 → Download from Cisco, then Restart.
6. To stop everything, press Ctrl+C in the Admin console window. The Broker and all workers run in that window and stop with it.

The release is self-contained: no .NET installation is needed. Its README.txt lists every port and first-run prompt.

Hardware

• CPU (server): OpenH264 is a software encoder, so video encoding runs entirely on the CPU and each streaming session runs its own encoder. From our testing: 6 cores minimum, 8 or more recommended, more for several sessions at once or high resolutions. The encoder uses up to min(cores, 8) threads by default (Encoder Settings → Thread cap). JPG mode needs no video encoder but still costs CPU per frame.
• GPU (server): not needed. Disable GPU is on by default.
• Viewer (client): a browser with hardware H.264 decoding (any normal PC or phone) gives the smoothest picture. In a VM or on a machine without a GPU, the browser decodes in software: it still works, just slower.

Build from source

Requirements: Windows x64, .NET 10 SDK.

CEF version: 154.0.33+ga03e714+chromium-154.0.8037.94 (Chromium 154), Windows 64-bit minimal distribution.

get-cef.ps1 downloads it for you automatically. To download it manually, get:

cef_binary_154.0.33+ga03e714+chromium-154.0.8037.94_windows64_minimal.tar.bz2

The archive is about 165 MB. All CEF builds are available at cef-builds.spotifycdn.com.

Then pass the downloaded archive to get-cef.ps1:

.\get-cef.ps1 -FromArchive "C:\path\to\cef_binary_154.0.33+ga03e714+chromium-154.0.8037.94_windows64_minimal.tar.bz2"

The archive must be exactly this version, because CefGlue's bindings are generated for this CEF version.

powershell -ExecutionPolicy Bypass -File .\get-cef.ps1      # download the CEF runtime (once)
dotnet build CefAsService.sln -c Release -p:Platform=x64

Then run CefGlue.Broker.Admin\bin\x64\Release\net10.0\Xilium.CefGlue.Broker.Admin.exe and continue from step 3 above.

Command-line flags

Pass them to the Admin exe; it forwards everything except --auto-start-broker to the Broker it starts.

Flag	Effect
--auto-start-broker	Start the Broker right away, without pressing Start
--use-webrtc	Use the WebRTC transport instead of WebSocket (fixed while the Broker runs). The video encoder defaults to OpenH264, which must be downloaded first
--isolation-mode-session	Give every tab its own persistent browser context (default: one per tenant)
--enc-openh264	Use OpenH264 video by default. Without an encoder, sessions start with plain JPG frames
--port-mode	Clients connect straight to the worker port instead of through the Broker relay
--no-selfsigned-https	Turn off the built-in self-signed HTTPS. Use this behind a reverse proxy (Caddy, Nginx) with a real certificate

Ports

Port	What	Reachable from
57402	Admin web UI	this machine only
57401	Admin ↔ Broker control channel	this machine only
57400	Broker HTTP (workers, API); browsers are sent on to 57443. With --no-selfsigned-https it serves the page itself, for a tunnel or reverse proxy (see How CAS works)	LAN
57443	Broker HTTPS: the page clients open. Also the target for a tunnel (see How CAS works)	LAN (the one to open in the firewall)

In the default relay mode, 57443 is the only port other devices need. --port-mode also needs the worker ports (set a fixed range with CEFGLUE_WORKER_PORT_RANGE_START / _END), and WebRTC sends media over UDP on dynamic ports (use a TURN server across NATs). Every default port can be changed with an environment variable: CEFGLUE_BROKER_ADMIN_UI_PORT, CEFGLUE_BROKER_ADMIN_PORT, CEFGLUE_BROKER_PORT, CEFGLUE_BROKER_HTTPS_PORT.

Running on Windows

• No "Run as administrator" needed. Admin, Broker and workers run as a normal user: every port is above 1024, and the self-signed certificate goes into your own (CurrentUser) certificate store.
• Firewall: the first time, Windows asks to allow the Broker and the worker on the network. Clicking Allow access may show a UAC prompt, because creating a firewall rule needs admin rights; the app itself still runs as a normal user. If you decline, only this machine (localhost) can connect.
• Certificate prompt: on the first Start, Windows asks to install the Broker's self-signed certificate. Yes makes https://localhost:57443 warning-free on this machine. No is fine too, the browser just shows a warning.
• Extract to a writable folder, not C:\Program Files: the OpenH264 download is written next to the executables. Settings (broker.db, one SQLite file shared by Admin, Broker and workers), browser profiles and caches live in C:\ProgramData\CefGlue (a hidden folder).
• Don't mix elevated and normal runs. Files created while running as administrator may not be writable by a normal run afterwards. Pick one and stick to it.

Projects

Folder	What it is
CefGlue, CefGlue.Common, CefGlue.Common.Shared, CefGlue.BrowserProcess	CefGlue: .NET bindings for CEF (Xilium/OutSystems, MIT), with changes
CefGlue.Headless, CefGlue.Headless.Server	Off-screen browser host and frame transport
CefGlue.Headless.Service	Worker process, one per client session
CefGlue.Broker	Assigns workers to clients, relays traffic, serves the viewer page
CefGlue.Broker.Admin	Admin web UI
CefGlue.Common.Encoder	Encoder plugin contract + built-in JPG
lib/	Prebuilt components (binary only, see LICENSE-BINARY.txt)

Video encoders & OpenH264

The OpenH264 plugin is included, but Cisco's openh264.dll is not. Cisco's free H.264 patent coverage applies only when the end user downloads Cisco's binary, so you fetch it on your own machine:

• Admin → Encoder Settings → openh264 → Download from Cisco, or
• powershell -ExecutionPolicy Bypass -File .\get-openh264.ps1 (after building; -Remove undoes it). The release zip also has get-openh264.cmd, which doesn't need PowerShell.

The download is checked against a fixed SHA-256 and must be version 2.6.0. You can also get it by hand: download https://ciscobinary.openh264.org/openh264-2.6.0-win64.dll.bz2, extract it, rename it to openh264.dll and put it in the worker's plugins/encoders/openh264/. Admin → Encoder Settings then checks its SHA-256 and warns if it is a different build.

OpenH264 Video Codec provided by Cisco Systems, Inc. Cisco's patent coverage is for personal and non-commercial use. A paid service that streams H.264 may need its own H.264 patent license.

WebRTC mode needs a video encoder. WebSocket mode can also stream plain JPG frames.

Security notes

• The Admin UI and the control channel are loopback-only by design. Don't expose them.
• Worker pages run in a real browser on your server. Treat whoever reaches /broker as someone using that machine's network.
• For public deployments, put a reverse proxy with a real certificate in front and use --no-selfsigned-https.
• Workers run with media streaming enabled (needed for audio), so a page opened in a worker can use the server's microphone or camera without a prompt. On a server with a microphone, keep that in mind.
• DevTools gives full control of a tab, including its cookies and storage in readable form. It is off by default; only switch it on for viewers you trust.
• Session recording is off by default. Turning it on in Admin means accepting responsibility for how it is used on your server.

Release history

v0.2.1

• Upgraded to CEF 154 (Chromium 154.0.8037.94).
• Added Mobile device mode: Chrome DevTools' device list (iPhone, Pixel, Galaxy, iPad, foldables and more) with each device's user agent, Client Hints and touch, plus rotation and device zoom.
• Added session recording: video (MP4) and audio only (MP3), with recording settings in Admin.
• The view mode (Clip / Responsive / Mobile) is now per tab.
• Fixed <select> dropdowns showing blank or closing right away when many tabs (12+) were open, or after a Broker restart.
• Fixed a Mobile tab losing its device user agent after a viewer reload or a Broker restart.
• Esc now exits a page's fullscreen, like in Chrome.
• "+" now switches to the new tab and scrolls it into view in the sidebar.
• Sharper text in Mobile mode, and a toolbar that moves the device controls into the menu when narrow.
• Added DevTools in the viewer: Chromium's own DevTools per tab in a resizable side panel, switched on in Admin.
• Added drag and drop inside the page, with a drag preview; links can be dropped on the address bar or the sidebar.
• Recording ID: each recording carries only a signed ID; the details are kept in a server-side recording log (retention set in Admin), with lookup by ID or file SHA-256 in Admin. Admin asks for confirmation before recording is switched on.
• Changing the device in Mobile mode reloads the page for the new screen size.
• Fixed a large Mobile-mode device being cut off at the top in WebRTC mode.
• The sidebar shows the number of open pages, and a Mobile tab's device icon turns into the close button on hover.

v0.2.0

• Withdrawn, replaced by v0.2.1 (session recorder hardening).

v0.1.0

• First release.

License

• Source code: MIT. See LICENSE (CefGlue, Xilium/OutSystems) and the LICENSE file in each project folder.
• Prebuilt components in lib/: free for personal and commercial use, binary only. See LICENSE-BINARY.txt.
• Third-party native libraries (libdatachannel, OpenSSL, Opus, libyuv, OpenH264, SQLite, LAME) keep their own licenses in the LICENSE-* / COPYING-* files next to them. CEF/Chromium: BSD.