Show HN: Turbo-Browser-MCP – Batch forms, DOM deltas and submit guards for MCP

A developer released turbo-browser-mcp, a Playwright-based Model Context Protocol server that consolidates 25-33 fine-grained browser primitives into 10 batched tools to cut token use and multi-turn latency in LLM browser automation. Benchmarks run in headless Chromium with OpenAI o200k_base tokenization (tiktoken 0.14.0) show a dense 140-button UI snapshot at 1,135 tokens versus 18,654 for HTML (93.9% savings), a 10-field form completed in 1 turn at 811 tokens versus 11 turns and 12,197 direct tokens (7x faster, 93.4% direct savings), and a 48 KiB PDF upload at 85 tokens versus 44,728 tokens inline Base64 (99.8% saved). The server ships delta DOM snapshots, single-turn React/Shadow DOM/iframe form prefill, disk-path file uploads, parallel tab sessions, network blocking presets and a default human-in-the-loop Submit guard.

turbo-browser-mcp is a Playwright-based Model Context Protocol MCP server built to cut LLM token waste and multi-turn latency in browser automation. It consolidates 25-33 fine-grained browser primitives into 10 batched tools featuring delta DOM snapshots, single-turn React/Shadow DOM/iframe form prefill, direct disk file uploads no Base64 in context , parallel tab sessions, network blocking presets, and a default human-in-the-loop Submit guard. All figures below come from benchmarks/benchmark.mjs https://github.com/Tthanh2k6/turbo-browser-mcp/blob/main/benchmarks/benchmark.mjs npm run benchmark running headless Chromium locally with exact OpenAI o200k base tokenization tiktoken 0.14.0 : | Capability | Typical Baseline | turbo-browser-mcp | Speed / Turn Gain | Token Savings o200k base | |---|---|---|---|---| | Dense UI Snapshot 140-btn SaaS console | 18,654 tok HTML / 3,568 tok full ARIA | 1,135 tok compact 28 ms | 1 call | 93.9% vs HTML 68.2% vs ARIA | | Post-Click Delta Snapshot onlyChanged: true | 3,582 tok full ARIA rescan | 56 tok changed lines 18 ms | 1 call | 98.4% vs ARIA 99.7% vs HTML | | 10-Field Complex Form + Snapshot smart fill form | 11 turns 574 ms , 12,197 dir / 72,614 cum tok | 1 turn 82 ms , 811 tok | 7x faster , 11 - 1 turns | 93.4% direct / 98.9% cumulative | | 48 KiB PDF Upload 49,152 bytes | 44,728 tok inline Base64 tool arg | 85 tok disk path 68 ms | Zero Base64 generation | 99.8% saved | | 6-Step Interactive UI Flow batch actions | 6 turns 411 ms , 955 dir / 3,162 cum tok | 1 turn 357 ms , 406 tok | 1.15x faster , 6 - 1 turns | 57.5% direct / 87.2% cumulative | | Open 6 Tabs Concurrently open many | 6 turns sequential 998 ms | 1 turn batched 420 ms | 2.38x faster , 6x fewer turns | 5 fewer prompt replays | | Heavy Media Load preset: "turbo" , 304 KiB assets | 252 ms , 9 media requests 304 KiB | 165 ms , 0 media requests 0 KiB | 1.53x faster | 100% media bandwidth cut | | Article Markdown Scraping extract clean text | 3,595 tok raw HTML 10,844 chars | 156 tok clean Markdown 641 chars | Clean reader output | 95.7% saved | | Diagnostics Triage page diagnostics errors-only | 3,460 tok unfiltered 32 req / 26 console | 601 tok default errors 2 req / 6 console | Zero noise scrolling | 82.6% saved | | Static MCP Tool Schema every turn overhead | 3,917 tok Playwright / 6,737 tok DevTools | 3,010 tok stripped 3,314 full w/ annotations | 10 tools vs 25 / 33 | 23.2% vs Playwright / 55.3% vs DevTools | Note on latency vs LLM inference turns: Eliminating 10 round-trips on a 10-field form saves both 7x in browser execution 574 ms - 82 ms and 10 separate LLM inference round-trips 2-5s per turn in agent loops plus ~71,800 replayed history tokens. Standard MCP servers charge an LLM round-trip for every snapshot, field fill, <select choice, upload, and verification check. Each turn re-sends the growing conversation history back into the model. sequenceDiagram autonumber participant Agent as LLM Agent participant Std as Standard MCP Playwright / DevTools participant Turbo as turbo-browser-mcp Note over Agent,Std: Standard MCP 12+ LLM turns, full ARIA tree + history replay each step Agent- Std: 1. snapshot - full ARIA ~3,568 tok loop Repeats 10+ times across fields, selects, checkboxes, upload Agent- Std: fill / select option / click Std-- Agent: full ARIA or confirmation re-added to history end Agent- Std: 12. upload inline or click chooser Note over Agent,Turbo: turbo-browser-mcp 2 LLM turns total, delta & inline snapshot Agent- Turbo: 1. inspect compact mode: "forms" - compact refs 1,135 tok Agent- Turbo: 2. smart fill form fields: ...10 fields + disk PDF... , returnSnapshot: true Turbo-- Agent: Filled 10 fields + guarded before Submit + inline snapshot 811 tok - 4 connection modes --mode auto|cdp|persistent|launch : - auto default : probes --cdp http://127.0.0.1:9222 first so agents can reuse an existing signed-in browser session, then falls back to launching Chromium. - cdp : attach directly to a running Chromium/Chrome/Edge remote debugging port. - persistent : launch with a reusable --user-data-dir profile across runs. - launch : start a clean browser session --headless by default, or --headed . - Auto binary discovery src/playwright-loader.mjs : checks playwright-core cache revisions across Windows, macOS, and Linux, system installs of Google Chrome, Microsoft Edge, Brave, and Chromium, or an explicit --executable <path . - Per-tab isolation tabs batch : open tabs inside named isolatedContext sandboxes with separate cookies and storage, batch-open up to 10 concurrent URLs open many , activate, reload, go back / forward , resize viewport, and emulate colorScheme , media , reducedMotion , contrast , forcedColors , or custom userAgent . - Snapshot modes: interactive , forms , article , and all . - Cross-boundary traversal: flattens main frame DOM, child iframes includeFrames , frameIdx , and open Shadow DOM. Injects an init script hooking Element.prototype.attachShadow WeakMap + WeakRef / FinalizationRegistry + window. tbmGetShadowRoot to keep post-init closed Shadow roots inspectable and guarded, traverses <slot assignedNodes { flatten: true } , and supports Form-Associated Custom Elements. - Token controls: onlyChanged: true emits only elements added or changed since the prior snapshot; query filters by regex or substring; boxes: true adds box=x,y,w,h only when needed; maxChars caps payload size; savePath writes full output to disk. Prefills an entire form in one MCP call while flushing microtasks and macrotasks between controlled inputs: - Standard & framework inputs: text, email, password, number, date, textarea, <input type="range" , checkboxes, radio groups check , not , overwrite . Triggers React-controlled state updates via native property setters and synthetic events. - Selects & custom widgets: <select and <select multiple option / values , ARIA comboboxes, ARIA switches, contenteditable rich editors, and Gmail compose dialogs gmail: { to, subject, body } . - Frame & wildcard targeting: target specific iframes via frameIdx , or set all: true to populate matching controls across frames. - Direct disk uploads: pass file or files paths directly to Playwright setInputFiles without loading binary files or Base64 strings into LLM context. - Atomic verification: pass returnSnapshot: true to inspect the updated form state in the same tool response. - act fast actions: click , dblclick , hover , focus , clear , fill , type slowly , delayMs , submit , select , check , uncheck , drag , drop file , files , or custom MIME dropData , press key + modifiers : Alt , Control , ControlOrMeta , Meta , Shift , scroll dx , dy , wait ms , state , loadState , text , textGone , url , and upload . - Targeting options: compact eN ref , CSS selector , visible text , label , or viewport x, y coordinates, with button left , right , middle and frameIdx . - batch actions : runs an ordered list of DOM actions and nested smart fill form steps in one MCP call, stopping safely if blocked by the Submit guard or optionally continuing on step errors continueOnError . - extract clean text : extracts readable plain text or compact Markdown format: "text" | "markdown" from main/article containers and iframes, stripped of script and style noise. - evaluate js : runs JS expressions or el, arg element functions in any frame frameIdx with JSON-serialized results and optional savePath export. - capture page : full-page or element-scoped screenshots png or jpeg with quality , css or device scale, optional returnImage and PDF generation saved to a confined savePath . - network session presets: turbo , no-images , no-media , and clean unblock all , alongside custom blockResources and blockUrls patterns. - Session & storage management: read/write/clear browser cookies , localStorage / sessionStorage , and export or reload full Playwright storageState JSON files saveStorageStatePath , loadStorageStatePath . - page diagnostics : defaults to errors-only level: "errors" , statusFilter: "errors" to surface failures cleanly without flooding context, while supporting all , includeStatic , urlFilter , deep request/response inspection reqId + part , completed downloads, and dialog auto-handling dialogPolicy : accept / dismiss . Run the benchmark suite yourself with Chromium and Playwright installed: npm run benchmark Environment & methodology: Headless Chromium via playwright-core , counting exact OpenAI o200k base tokens via Python tiktoken approx-bpe fallback if tiktoken is unavailable . Cumulative workflow tokens model standard chat-history replay across | Scenario | Raw HTML | Full Playwright ARIA | turbo-browser-mcp Output | Saved vs ARIA | Saved vs HTML | |---|---|---|---|---|---| | 140-Button SaaS Console inspect compact | 61,010 chars 18,654 tok | 12,771 chars 3,568 tok | 3,968 chars 1,135 tok | 68.2% | 93.9% | | Post-Click Delta onlyChanged: true | 61,010 chars 18,654 tok | 12,825 chars 3,582 tok | 168 chars 56 tok | 98.4% | 99.7% | | Article Markdown Extraction extract clean text | 10,844 chars 3,595 tok | n/a | 641 chars 156 tok | n/a | 95.7% | | Diagnostics Filter 32 reqs, 26 console logs | 9,651 chars 3,460 tok, all | n/a | 1,761 chars 601 tok, errors | n/a | 82.6% | | Scenario | Step-by-Step Baseline | turbo-browser-mcp | Execution Speedup | Token Savings | |---|---|---|---|---| | 10-Field Complex Form + Verify smart fill form | 11 turns, 574 ms , 12,197 direct / 72,614 cum tok | 1 turn , 82 ms , 811 tok filled=10 | 7x faster | 93.4% dir / 98.9% cum | | 48 KiB PDF Upload 49,152 bytes via file | 65,679 chars 44,728 tok Base64 payload | 263 chars 85 tok disk path 68 ms | Zero LLM Base64 encode | 99.8% | | 6-Step UI Flow batch actions | 6 turns, 411 ms , 955 dir / 3,162 cum tok | 1 turn , 357 ms , 406 tok | 1.15x faster | 57.5% dir / 87.2% cum | | Open 6 Tabs tabs batch open many , 60 ms TTFB | 6 turns sequential 998 ms | 1 turn batched 420 ms | 2.38x faster 6 - 1 turns | Eliminates 5 turns | | Heavy Media Load 8x32 KiB imgs + 48 KiB font | 252 ms , 9 media hits 304 KiB | 165 ms , 0 media hits 0 KiB | 1.53x faster | 100% media saved | Measured against installed MCP JSON schemas on disk compact parameter schemas without annotations : | MCP Server | Tool Count | Compact Schema Chars | Exact o200k base Tokens | Savings with turbo-browser-mcp | |---|---|---|---|---| | turbo-browser-mcp | 10 14,186 full / 12,796 compact | 12,796 | 3,010 3,314 full w/ annotations | Baseline 10 tools | | @playwright/mcp | 25 | 18,457 | 3,917 | 23.2% fewer static tokens | | chrome-devtools-mcp | 33 | 30,252 | 6,737 | 55.3% fewer static tokens | | Feature | turbo-browser-mcp | @playwright/mcp | chrome-devtools-mcp | |---|---|---|---| | Tool Surface Size | 10 batched tools | 25 granular tools | 33 granular tools | | Delta Snapshots onlyChanged | Built-in | Full tree every snapshot | Full tree every snapshot | | Closed Shadow DOM Hook | Post-init attachShadow hook + <slot flattening | Open Shadow DOM | CDP / standard DOM access | | Single-Call Smart Form + Contenteditable | Yes React, Shadow DOM, iframe, Gmail, ranges | Multi-turn fill + separate select calls | Basic fill form | | Disk File Upload Zero Base64 | Native file / files path in smart fill form & act fast | Dedicated browser file upload turn | Dedicated upload file turn | | Default Human-in-the-Loop Submit Guard | Yes allowSubmit=false , form/iframe/Enter hooks | No | No | | Parallel open many + isolatedContext | Single batched call | Separate sequential tab calls | Separate page calls | | One-Call turbo Media Blocker | Built-in turbo , no-images , no-media | Manual JS / routing | Network emulation | | Performance / Heap Profiling | Not included | Not included | Trace, Lighthouse, Heap Snapshot | When to keep Chrome DevTools MCP alongside turbo-browser-mcp : chrome-devtools-mcp provides Lighthouse audits, performance trace analysis, CSS computed style panels, and V8 heap snapshots. turbo-browser-mcp focuses on fast multi-step UI automation, forms, and scraping with minimal token overhead. | Capability | turbo-browser-mcp | @playwright/mcp | chrome-devtools-mcp | |---|---|---|---| | Multi-tab open, list, switch, resize, emulate | tabs batch | browser tabs , browser navigate , browser resize , ... | new page , list pages , select page , resize page , ... | | DOM / accessibility inspection | inspect compact | browser snapshot | take snapshot | | Multi-field form & upload | smart fill form | browser fill form + browser select option + browser file upload | fill form + upload file | | Click, type, drag, press, scroll, wait | act fast | browser click , browser type , browser drag , ... | click , type text , drag , press key , wait for | | Multi-step sequential macro | batch actions | browser run code unsafe or N tool calls | N separate tool calls | | Clean article extraction | extract clean text | browser evaluate custom JS | evaluate script custom JS | | Frame/element JS evaluation | evaluate js | browser evaluate | evaluate script | | Errors, network & console triage | page diagnostics | browser console messages , browser network requests | list console messages , list network requests , ... | | Screenshots & PDF export | capture page | browser take screenshot | take screenshot | | Blocking presets, cookies & storage | network session | browser evaluate + context config | Partial via evaluate script / emulate | 1. Human-in-the-loop Submit Guard allowSubmit=false by default : - smart fill form stopBeforeSubmit: true , act fast , and batch actions inspect matching elements, W3C AccName labels isSafeSubmitter , implicit HTML form Enter submissions, key chords Shift+Enter , Enter+Shift , HTMLFormElement.prototype.submit / requestSubmit , and same-origin iframe contentWindow / contentDocument proxies. - Final actions resembling Submit , Publish , Send , Post , Apply , Confirm , or payment triggers are blocked unless allowSubmit: true is explicitly passed or --allow-submit is enabled at startup. - Trade-off: pre-existing closed Shadow roots on already-open CDP tabs attached before the init script ran or strict cross-origin sandboxed frames fall back to Playwright frame handles, coordinate actions, and keyboard input. 2. Workspace Path Confinement TURBO BROWSER SAVE ROOT : - File outputs savePath , saveStorageStatePath and state inputs loadStorageStatePath are strictly confined to the current working directory or TURBO BROWSER SAVE ROOT . - Lexical checks, lstatSync / readlinkSync symlink verification, and realpathSync validation block .. traversal, UNC network paths, dangling symlinks, cyclic symlinks, and Windows junctions before reading or writing. 3. File outputs | Tool | Purpose | Key Parameters | |---|---|---| | tabs batch | Ordered tab & browser lifecycle | operations list , open , open many , navigate , activate , resize , emulate , reload , back , forward , close , close browser , isolatedContext , concurrency 1-10 | | inspect compact | Token-capped element/form/article snapshot | mode interactive , forms , article , all , onlyChanged , query , boxes , maxChars , includeFrames , savePath | | smart fill form | Batch form, editor & disk file prefill | fields ref , selector , value , option , values , check , not , keys , file , files , frameIdx , all , gmail , overwrite , stopBeforeSubmit , returnSnapshot | | act fast | Single targeted page action | action 16 actions , ref / selector / text / label / x, y , modifiers , dropData , allowSubmit , returnSnapshot | | batch actions | Ordered chain of actions + form steps | steps , continueOnError , allowSubmit , returnSnapshot , snapshotMaxChars | | extract clean text | Clean text or compact Markdown reader | format text , markdown , selector , includeFrames , maxChars , savePath | | evaluate js | Scoped JS expression or el, arg call | expression , arg , frameIdx , ref / selector / text , savePath | | page diagnostics | Console, network, downloads & dialogs | level errors , all , statusFilter errors , all , includeStatic , urlFilter , reqId , part , dialogPolicy , clear , savePath | | capture page | PNG/JPEG screenshots & PDF export | mode screenshot , pdf , type , quality , fullPage , scale css , device , ref / selector / text , returnImage , savePath | | network session | Resource blockers, cookies & storage | preset turbo , no-images , no-media , clean , blockResources , blockUrls , cookieAction , storageAction , loadStorageStatePath , saveStorageStatePath | { "name": "smart fill form", "arguments": { "fields": { "selector": " full name", "value": "Alex Nguyen" }, { "selector": " email", "value": "alex@example.com" }, { "selector": " country", "option": "United States" }, { "selector": " skills", "values": "TypeScript", "Playwright" }, { "selector": " agree terms", "check": true }, { "selector": " resume pdf", "file": "./assets/resume.pdf" } , "stopBeforeSubmit": true, "returnSnapshot": true } } { "name": "inspect compact", "arguments": { "mode": "interactive", "onlyChanged": true, "maxChars": 3000 } } { "name": "tabs batch", "arguments": { "operations": { "action": "open", "url": "https://example.com/app", "isolatedContext": "acct-a" }, { "action": "open many", "urls": "https://example.com/docs", "https://example.com/pricing" , "concurrency": 4 } } } git clone https://github.com/Tthanh2k6/turbo-browser-mcp.git cd turbo-browser-mcp npm install npm run doctor If you need Playwright's bundled Chromium or have no system Chrome/Edge/Brave installed : npx playwright-core install chromium Using local clone: { "mcpServers": { "turbo-browser": { "command": "node", "args": "/absolute/path/to/turbo-browser-mcp/src/index.mjs" , "env": { "TURBO BROWSER SAVE ROOT": "/absolute/path/to/allowed/workspace" } } } } Using npx / binary entrypoint: { "mcpServers": { "turbo-browser": { "command": "npx", "args": "-y", "turbo-browser-mcp" } } } | CLI Flag | Environment Variable | Default | Description | |---|---|---|---| | --mode <auto\|cdp\|persistent\|launch | TURBO BROWSER MODE | auto | Connection strategy cdp first then launch in auto | | --cdp <url | TURBO BROWSER CDP URL | http://127.0.0.1:9222 | Chrome DevTools Protocol HTTP endpoint | | --user-data-dir <path | TURBO BROWSER USER DATA DIR | "" | Persistent profile directory path | | --executable <path | - | auto-detected | Custom Chromium, Chrome, Edge, or Brave executable | | --timeout <ms | TURBO BROWSER TIMEOUT MS | 15000 | Default Playwright action/navigation timeout in ms | | --headless / --headed | TURBO BROWSER HEADLESS | true headless | Run headless or visible browser window "false" for headed | | --allow-submit | - | false | Disable default Submit/Publish confirmation guard | | --doctor | - | - | Print Node, Playwright, Chromium, and CDP diagnostics as JSON | | --version / -v | - | - | Print server version 0.4.0 | | --help / -h | - | - | Print CLI usage summary | | - | TURBO BROWSER SAVE ROOT | process.cwd | Root directory confining savePath and storageState files | | - | PLAYWRIGHT CORE PATH | auto-resolved | Explicit path to playwright-core/index.mjs | Tip - Reusing your logged-in Chrome tabs: Enable remote debugging on port 9222 via chrome://inspect/ remote-debugging or launching Chrome with --remote-debugging-port=9222 . In default --mode auto , turbo-browser-mcp attaches to your open tabs directly instead of launching a fresh unauthenticated browser. npm test 405 passing tests across 85 suites 25 test files under test/ .test.mjs npm run doctor Environment check for Node, Playwright, Chromium, and CDP npm run benchmark Local Chromium speed & exact o200k base token benchmark Tested automatically on GitHub Actions ubuntu-latest across Node 20 and Node 22 .