Plasmate SOP

Appearance

Plasmate SOPThe browser engine for AI agents.

HTML in. Semantic Object Model out. 10x token compression, 50x faster than Chrome.

Overview ​

Plasmate is an open-source, agent-native headless browser engine written in Rust. It compiles HTML into a Semantic Object Model (SOM) -- a structured, token-efficient representation that LLMs can reason about directly. It replaces the Chrome DevTools Protocol (CDP) with a purpose-built Agent Web Protocol (AWP) that has exactly 7 methods.

Why it matters ​

PlasmateLightpandaChrome
Per page4-5 ms23 ms252 ms
Memory (100 pages)~30 MB~2.4 GB~20 GB
Binary size43 MB (macOS arm64)59-111 MB300-500 MB
Output formatSOM (10-800x smaller than HTML)Raw HTMLRaw HTML
LicenseApache 2.0AGPL-3.0Chromium

Token cost per 1,000 pages/day with GPT-4o: $99 in raw HTML tokens vs $5.69 in SOM tokens. Same content, 94% lower cost.

Key concepts ​

  • SOM (Semantic Object Model): A DOM projection that strips rendering/layout/styling and keeps only structure, content, and interactive elements. Not lossy compression -- a different representation for a different purpose.
  • AWP (Agent Web Protocol): 7 intents -- navigate, snapshot, click, type, scroll, select, extract. Agents express intent; Plasmate handles implementation. CDP compatibility included as a legacy bridge.
  • SOM Cache: Hosted API that compiles any URL to SOM on demand. Zero infrastructure required. No API key needed for public pages. Shared CDN with cached results.
  • W3C: Plasmate is a member of the W3C Web Content and Browser AI Community Group. SOM and AWP are being developed as open web standards.

Safety and ToS notes ​

Plasmate is Apache 2.0. No proprietary license restrictions. The hosted SOM Cache is a shared service -- do not hammer public endpoints at abusive rates. For high-volume production workloads, run the self-hosted binary. The binary currently supports Linux and macOS only (x86_64 and arm64); Windows support is not mentioned in v0.1.1.