Firefox DevTools MCP runs on your own machine — the client starts it, so there is no endpoint to ping. 7 153 installs a week from npm. Last commit 30 Oct 2026.
Control and debug Firefox: navigate, fill forms, inspect network and console, profile.
What the code does
We read the source, 3 h ago · rules 995398eba69f
What this server is able to do. For an MCP server this is often the job itself — a terminal server runs commands because that is what it is for. Listed so you know what you are plugging in, not as an accusation.
const output = execFileSync(regExecutable(), ['query', key, '/ve'], {
subprocess.run(
Is this your server and something here is wrong? Tell us — corrections are free and do not require a plan.
This code can reach further than it looks
We found places where it runs commands, builds paths or queries from values it is given. None of that is a flaw by itself — it becomes one when the code changes, and code changes quietly between releases. We re-read it on every one.
Connect this server
This server runs on your own machine — install it with the package manager and the client starts it for you. Package name taken from the official registry entry.
claude mcp add firefox-devtools-mcp -- npx -y @mozilla/firefox-devtools-mcp{
"mcpServers": {
"firefox-devtools-mcp": {
"command": "npx",
"args": [
"-y",
"@mozilla/firefox-devtools-mcp"
]
}
}
}[mcp_servers.firefox-devtools-mcp]
command = "npx"
args = ["-y", "@mozilla/firefox-devtools-mcp"]{
"mcpServers": {
"firefox-devtools-mcp": {
"command": "npx",
"args": [
"-y",
"@mozilla/firefox-devtools-mcp"
]
}
}
}{
"servers": {
"firefox-devtools-mcp": {
"type": "stdio",
"command": "npx",
"args": [
"-y",
"@mozilla/firefox-devtools-mcp"
]
}
}
}Optional settings from the registry entry, left out of the block above:
FIREFOX_HEADLESS (Set to true to run Firefox without a visible window), START_URL (URL to open when the server starts).
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Firefox DevTools MCP — questions
Answers built from our own checks of this server.