pxtree

pxtree

Loads a webpage in headless Chromium and prints what actually rendered as a compact text tree, so an AI coding agent can check a layout without a screenshot.

A dev server page with a row of three cards, a row of three plans, a list of steps, a row of stats, an article, a form, a column of prices and a row of tiles:

$ npx -y pxtree@latest localhost:5173

1280x800 light dpr 1 ltr scroll 0/382 page 1280x1182 painted to 1134 since last run: no changes summary: 7 findings a.button tops 64..136 across siblings: ul.cards div.stat tops 0..6 across siblings: div.stats input.field starts 0..3 across siblings: form.fields 12 wider than li.plan: li.plan.featured 72 taller than li.card: li.card 3 of 3 20 shorter than div.tile: div.tile.short gaps 16 16 24 16 between li.step: ul.steps body 1280x1182 pad 24 ul.cards 1232x208 gaps across 16, free 600 at end li.card 200x136 pad 16[renders background] h3 "Starter" 168x24 [text 19/24] p "Short text." 168x24 @0,32 [text 16/24] a.button "Choose" 168x40 @0,64 pad 8 16[renders background] li.card 200x136 @216,0 pad 16[renders background] h3 "Team" 168x24 [text 19/24] p "Short text." 168x24 @0,32 [text 16/24] a.button "Choose" 168x40 @0,64 pad 8 16[renders background] li.card 200x208 @432,0 pad 16renders background h3 "Business" 168x24 [text 19/24] p "A much longer…" 168x96 @0,32 [text 16/24, 4 lines, 444 on one line] a.button "Choose" 168x40 @0,136 pad 8 16[renders background] ul.plans 1232x56 @0,232 [gaps across 16, free 588 at end] li.plan "Monthly" 200x56 pad 16[renders background] li.plan "Yearly" 200x56 @216,0 pad 16[renders background] li.plan.featured "Lifetime" 212x56 @432,0 pad 16renders background ul.steps 1232x192 @0,312 gaps 16 16 24 16 li.step "One" 1232x24 [text 16/24] li.step "Two" 1232x24 @0,40 [text 16/24] li.step.active "Three" 1232x24 @0,80 [text 16/24] li.step "Four" 1232x24 @0,128 [text 16/24] li.step "Five" 1232x24 @0,168 [text 16/24] div.stats 1232x62 @0,528 gaps across 16, free 456 at end div.stat "Revenue" 182x56 pad 16[renders background] div.stat "Orders" 182x56 @198,0 pad 16[renders background] div.stat.alert "Refunds" 182x56 @396,6 pad 16[renders background] div.stat "Customers" 182x56 @594,0 pad 16[renders background] article 1232x132 @0,614 [gaps 12] h2 "First heading" 1232x24 [text 24/24] p "First paragraph." 1232x24 @0,36 [text 16/24] h2 "Second heading" 1232x24 @0,72 [text 24/24] p "Second paragraph." 1232x24 @0,108 [text 16/24] p.with-link "Read the first." 1232x24 @0,762 [text 16/24] a "guide" 39x17 @69,3 [text 16/24] form.fields 1232x108 @0,802 gaps 8 input.field "Name" 208x21 pad 1 2[renders background, border] input.field "Email" 208x21 @0,29 pad 1 2[renders background, border] input.field.nudged "Company" 208x21 @3,58 pad 1 2[renders background, border] input.field "Phone" 208x21 @0,87 pad 1 2[renders background, border] div.prices 300x72 @0,934 span.price "$9" 18x24 @282,0 [text 16/24] …×2 similar span.price 36x24..49x24 div.tiles 1232x80 @0,1030 [gaps across 16, free 900 at end] div.tile 100x80 [renders background] div.tile.short 100x60 @116,0 renders background div.tile 100x80 @232,0 [renders background]

The first line is the facts line: viewport, color scheme, device pixel ratio, direction, scroll position out of the maximum, document size, and painted to, the lowest painted pixel. since last run compares with the previous run of the same URL and settings, or of the same --diff-key name. That history lives in ~/.cache/pxtree, never in your project, and --no-diff skips it.

The ul.cards line says the "Choose" buttons in the three cards have tops from 64 px to 136 px below the top of their card. The li.plan.featured "Lifetime" line says that plan is 212x56 at x 432 in its row, 12 px wider than the width its siblings share. Findings are measurements with a threshold, never verdicts. The agent decides from the code whether they are intended.

Why not a screenshot

• It gives numbers in CSS px, not pixels the model has to estimate.
• The agent reads it in one pass, as text, with the findings listed on top.
• One call covers several viewports and color schemes.

Install

pxtree drives Playwright's Chromium. Install it once, about 150 MB:

npx -y playwright@1.63.0 install chromium

pxtree itself downloads nothing and never edits your project. --channel chrome uses an installed Chrome instead. Needs Node 20 or newer.

MCP server

OpenCode, opencode.json:

{

"$schema": "https://opencode.ai/config.json", "mcp": { "pxtree": { "type": "local", "command": ["npx", "-y", "pxtree@latest", "mcp"], "enabled": true } } }

Other clients and config files

Any MCP client that reads mcpServers:

{

"mcpServers": { "pxtree": { "command": "npx", "args": ["-y", "pxtree@latest", "mcp"] } } }

VS Code, .vscode/mcp.json:

{

"servers": { "pxtree": { "type": "stdio", "command": "npx", "args": ["-y", "pxtree@latest", "mcp"] } } }

Amp, settings.json:

{

"amp.mcpServers": { "pxtree": { "command": "npx", "args": ["-y", "pxtree@latest", "mcp"] } } }

Zed, settings.json: