Google's Chrome DevTools MCP server gives a coding agent a real Chrome to drive. It takes a proxy in one flag, and that flag has one condition attached: it only applies when the server launches the browser itself. In the setup many agents use, where the server attaches to a Chrome that is already open, the value is dropped without a word. We read every setting on this page in release 1.9.0, published on 8 September 2026.
The one flag
npx chrome-devtools-mcp@latest --proxyServer="http://GATEWAY_HOST:GATEWAY_PORT"
The option's own description says what happens: the value is "passed as --proxy-server when launching the browser". The server builds the Chrome arguments, adds your address to them, and then decides which browser to use.
When it applies, and when it is ignored
| How the server gets a browser | Does --proxyServer apply? |
|---|---|
| It launches Chrome itself (the default) | yes, as a Chrome flag |
--browserUrl or --wsEndpoint | no, the connect path receives no Chrome arguments |
--autoConnect | no, same path |
That is the whole trap. The code builds the argument list first, so the flag looks accepted, and then hands it only to the launch path. The option declares no conflicts with the connect options, so the command line is valid and nothing warns. The same limit is written openly on the neighbouring flags: --chromeArg and --ignoreDefaultChromeArg both say they only apply when Chrome is launched by the server.
If you need the proxy with a Chrome you start yourself, put the flag on that Chrome instead. The server will then attach to a browser that is already routed.
What the flag can carry
The option is a plain string, so anything you write is accepted. Chrome decides what happens next, and Chrome ignores a login in that flag. It also supports no SOCKS5 authentication at all. This server adds nothing of its own: a search of the repository for the usual authentication handlers returns nothing.
So a line for this server has to work without a password.
Which proxy type fits it?
Residential, for the sites that refuse a hosting address. In our test of 19 September 2026 a residential address changed four of thirteen answers, while four sites refused both. That test sent plain requests rather than a browser. The table is on our OpenClaw page.
Because no login can travel, allow the machine's address instead. On an HProxy Residential Premium plan that is a plan feature, up to 150 addresses, and the flag then carries nothing secret at all. An allowed address takes no country or city targeting; it rotates on the rotating ports and holds one address per sticky port. An agent that works one site across several steps suits a sticky port. A sticky address can still change early if its device leaves the network, so let the agent retry. The residential proxies page lists the plans, and the plan API manages allowed addresses from code.
Keeping the session cheap
A browser loads everything a page asks for, and an agent session can run for a long time. This server can block requests by URL pattern, which is the simplest way to keep images, fonts and third party scripts off a metered line. Chrome also keeps localhost and link-local addresses direct by its own rules, so those never reach the proxy.
What breaks when the proxy is on
- The address never changes. The server attached to a running Chrome, so the flag was ignored.
- 407 Proxy Authentication Required. The line wants a password the flag cannot send. Allow the machine's address instead. Our 407 guide explains the error.
- Certificate errors through an inspecting proxy. The flag was added for exactly that case, which is why certificate handling sits next to it in the options.
- Traffic climbs during long sessions. Block what you do not need by URL pattern.
- The site still refuses. A proxy changes the address, not the browser or the way the agent behaves.
What this page does not cover
We read chrome-devtools-mcp 1.9.0 as text and did not run it, so the silent drop above follows from the arguments the connect path receives rather than from a capture of our own. Our blocking test used plain requests from one server address and one residential line, on one day. The server ships a release every few weeks, so we will read these settings again by 19 October 2026.
Where to go from here
Proxies for Playwright MCP covers the other big browser MCP server, which does take a login, in a config file. Proxies for agent-browser covers a CLI with the same attach problem and a different answer to the login. Proxies for Lightpanda covers a browser that takes the login in the address, because it is not built on Chrome.
Sources
- The browser options (src/config/browser-options.ts), the context builder that adds the flag and chooses the browser (src/index.ts), and the configuration documentation. ChromeDevTools/chrome-devtools-mcp, release 1.9.0, 8 September 2026.
- Issue 155 and pull request 230, which added the flag on 1 October 2025. Chrome DevTools MCP issue tracker.
- Credentials in the proxy flag, SOCKSv5 authentication and the implicit bypass rules. The Chromium Authors, net/docs/proxy.md, read 19 September 2026.
- Plans, IP whitelist and sticky sessions; errors; the proxy API. HProxy documentation, hproxy.com/docs, 19 September 2026.
- Our own test of 19 September 2026: plain GET requests to 13 sites and 3 controls, two runs from our server and two through a residential line of our own house plan. Raw output is kept in the research folder of our OpenClaw page.
