Substrate Browser

Name: Substrate Browser
Author: manuelinuxkr

by manuelinuxkrversion 2.0.2i★ –iRuns on your computer

Registry nameio.github.manuelinuxkr/substrate-browser

Install

Overview

Description from the maker (original English)

Token-first headless browser for AIs. Extracts a tiny semantic graph, cutting HTML bloat by 95%.

PopNx MCP’s three pillars

These three are never merged into one score: opinions, measurements and popularity are different things.

User voiceiNo reviews yetReviews open together with accounts in a later step
Our basic checksi1 of 1 passedChecked from public information; code not scanned yet
UsageiNot measured yet★ –

What you can do with it

We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.

Connection: Runs on your computer
Transport: stdio
Category: Web & browsers

Install

Pick the AI app you use, then copy the settings.

Before you install

Basic checks: 1 of 1 passed
Runs on your computer with your user’s permissions (files, network, apps).
You fill in yourself: SUBSTRATE_PROXY, SUBSTRATE_VIEWPORT_WIDTH, SUBSTRATE_VIEWPORT_HEIGHT

You need

npmNode.js installed (for the npx command)

Which app do you use?

ClaudeClaude CodeCursorVS CodeChatGPT

Pick your app above. We remember it, so next time the button says “Install in …”.

Open Claude Desktop → Settings → Developer → Edit Config, and paste this into claude_desktop_config.json

{
  "mcpServers": {
    "substrate-browser": {
      "command": "npx",
      "args": [
        "-y",
        "substrate-browser"
      ],
      "env": {
        "SUBSTRATE_PROXY": "your-value",
        "SUBSTRATE_VIEWPORT_WIDTH": "your-value",
        "SUBSTRATE_VIEWPORT_HEIGHT": "your-value"
      }
    }
  }
}

Run this in your terminal

claude mcp add substrate-browser --env SUBSTRATE_PROXY=your-value --env SUBSTRATE_VIEWPORT_WIDTH=your-value --env SUBSTRATE_VIEWPORT_HEIGHT=your-value -- npx -y substrate-browser

Fill in the empty values before running it.

Open in Cursor

Or copy the settings yourself

Paste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json

{
  "mcpServers": {
    "substrate-browser": {
      "command": "npx",
      "args": [
        "-y",
        "substrate-browser"
      ],
      "env": {
        "SUBSTRATE_PROXY": "your-value",
        "SUBSTRATE_VIEWPORT_WIDTH": "your-value",
        "SUBSTRATE_VIEWPORT_HEIGHT": "your-value"
      }
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

Open in VS Code

Or copy the settings yourself

Paste into .vscode/mcp.json in your project

{
  "servers": {
    "substrate-browser": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "substrate-browser"
      ],
      "env": {
        "SUBSTRATE_PROXY": "your-value",
        "SUBSTRATE_VIEWPORT_WIDTH": "your-value",
        "SUBSTRATE_VIEWPORT_HEIGHT": "your-value"
      }
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

This one runs on your computer, and ChatGPT can only connect to servers on the internet. Pick another app.

Your choice stays on this device in a cookie; no account needed.

Values you fill in

SUBSTRATE_PROXY env
Optional egress proxy URL (http/socks) to route all Chromium traffic through, mitigating SSRF and DNS rebinding risks.
SUBSTRATE_VIEWPORT_WIDTH env
Browser viewport width in pixels (Default: 1280)
SUBSTRATE_VIEWPORT_HEIGHT env
Browser viewport height in pixels (Default: 800)

These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.

What it can do

Runs on your computer; the tool list appears in your AI app after you install it.

Basic checksi

We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 7, 2026

✓ Pass
Maker matches the repo
The registry name was verified with the GitHub account manuelinuxkr, which owns the repo
… Not checked yet
Still maintained
We have not read this repo from GitHub yet
… Not checked yet
Has a licence
We have not read this repo from GitHub yet
– Not applicable
Endpoint responds
This one runs on your computer; there is no internet endpoint
– Not applicable
Sign-in with OAuth
Runs on your computer and uses local settings instead
… Not checked yet
No hidden instructions in tool descriptions
Runs on your computer; we can only read tool lists from internet endpoints

Compared with others in Web & browsersi

More stars than 0% of the other 879 servers in this category
Published to the registry more recently than 34% of the other 879 servers in this category
Basic checks equal to or better than 100% of the other 879 servers in this category

Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.

Common questions

Is Substrate Browser safe?

It passed 1 of 1 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.

What keys or codes does it need?

The registry does not list a required key, though some servers ask you to sign in on first use.

Does it run on my computer or in the cloud?

It runs on your computer. Your AI app starts it when needed, and data does not pass through the maker’s servers (unless it calls an online service itself).

Is it still maintained?

The GitHub repo last changed –, and the latest version (2.0.2) reached the registry 2 months ago.

Which apps can use it?

Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. You also need Node.js on your computer.

What can I use instead?

In the same category: Browser Use, Chrome DevTools MCP, MCP Server Browser

Alternatives

Servers in the same category from other makers, sorted by stars.

Reading a card:★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi

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Install

README from the maker

Open the README

Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.

Substrate

Stop wasting 48K tokens to read a webpage. Substrate compresses a typical content page into roughly 1–4K tokens your LLM can actually use — vs. ~48K of raw HTML.

Substrate is an MCP server that gives your AI agent eyes and hands on the web. It extracts a compressed semantic graph of any webpage — buttons, inputs, links, dropdowns, checkboxes — with precise pixel coordinates, and handles clicking, typing, and selection via spatial coordinates. No CSS selectors. No xpaths. No hallucination.

Why It Matters

Every other browser automation approach burns tokens on noise:

Approach	Tokens	Extraction	What Your LLM Gets
Raw HTML (`page.content()`)	~48,000	5ms	Full DOM tree — scripts, styles, hidden elements, ad markup. LLM drowns in noise and hallucinates clicks on invisible elements.
Vision (screenshot + OCR)	~8,000	~800ms	A pixel blob. LLM can "see" the page but can't target anything precisely. Clicks land 20px off. Forms fail.
Substrate	~1,000–4,000	~10–30ms	Structured JSON: what each element is, where it is, what state it's in. LLM clicks the right thing on the first try.

The math: a ~110-element content page (say, Wikipedia) compresses to roughly ~2,300 tokens — about 1.8% of a typical 128K context window. You can fit roughly ~55 page extractions before the LLM runs out of room. With raw HTML, you get 2.

*Token figures are order-of-magnitude, measured live on representative pages (example.com ~84 tok, Wikipedia ~3.5K, Hacker News front page ~4.4K, extraction 8–58ms). They scale with page density; the extractor caps output at MAX_ELEMENTS=400, so very dense pages are truncated rather than emitted in full. The math is arithmetic: on a ~2.3K-token page, ⌊128K/2.3K⌋ ≈ 55 extractions.*

The real win — shorter action loops:

Without Substrate:                          With Substrate:

navigate → screenshot navigate → "I see a button" → click (wrong) → {btn id=3 "Submit" [640,400]} → screenshot → "ah, more right" → click(3) → done. → click → "not that either" → screenshot → ... 2 tool calls. Task complete. 8-12 tool calls. Task complete.

That's not a marginal improvement. That's 5-6x fewer API calls, 5-6x less latency, and 5-6x lower cost per web task.

How It Works

Substrate runs as a headless Chromium browser via the Model Context Protocol (MCP). Your LLM agent talks to it through 10 simple tools:

Tool	What It Does
`navigate`	Load a URL, get back the page graph (capped at 400 elements)
`click`	Click any element by its numeric ID
`type_text`	Type into an input field (auto-clears first)
`select_option`	Pick a dropdown option by value
`press_key`	Press a keyboard key (Escape, Enter, Tab, arrows, modifiers)
`scroll`	Scroll up/down by 80% of viewport
`screenshot`	Get a visual snapshot + the graph together
`go_back` / `go_forward`	Browser history navigation
`get_current_url`	Check where you are

Every navigation and interaction tool returns the same compressed graph (get_current_url returns just the URL; screenshot returns the image plus the graph). Your LLM reads the graph, picks an element ID, and calls the next tool. No image interpretation. No HTML parsing. Just IDs and coordinates.

Installation & Setup

Substrate is a standalone Model Context Protocol (MCP) server. You do not need to write code to use it — you just plug it into your AI assistant.

Option 1: Claude Desktop (Recommended)

Open your Claude Desktop configuration file:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
Windows: %APPDATA%\Claude\claude_desktop_config.json

Add the substrate-browser server to the mcpServers block:

"mcpServers": { "substrate-browser": { "command": "npx", "args": ["-y", "substrate-browser"] } } }

3. Restart Claude Desktop. You will now see the 10 browser tools available (a small hammer icon) and you can ask Claude to "Go to example.com and tell me what you see".

*(Note: Playwright will automatically download the Chromium binary on the very first run. This requires Node.js 20+ installed on your system).*

Option 2: Running from Source (For Developers)

If you want to modify the extraction logic or add your own tools:

git clone https://github.com/manuelinuxkr/substrate-b.git

cd substrate-b npm install npx playwright install chromium npm run build npm start

License

MIT

Substrate Browser

Overview

PopNx MCP’s three pillars

What you can do with it

Install

Before you install

Values you fill in

What it can do

Basic checksi

Maker matches the repo

Still maintained

Has a licence

Endpoint responds

Sign-in with OAuth

No hidden instructions in tool descriptions

Compared with others in Web & browsersi

Common questions

Alternatives

Browser Use

Chrome DevTools MCP

MCP Server Browser

README from the maker

Substrate

Why It Matters

How It Works

Installation & Setup

Option 1: Claude Desktop (Recommended)

Option 2: Running from Source (For Developers)

License