Browserless vs Selenium

Browserless

An OpenAPI document, llms.txt and a 14-tool MCP server with annotations on every tool make the service easy for an agent to read, and the free plan needs no card. The API token travels in the URL query string by default, cloud tokens carry no scopes, and no machine payment route exists.

Selenium

Selenium is stable, Apache-2.0 software on 4.51.0 with bindings in five languages, CI passing on trunk, an llms.txt and an agent guide added in September 2026. It has no MCP server of its own, Selenium Manager sends usage statistics by default, and Grid accepts unauthenticated sessions unless a username and password are set.

Browserless

1. Send the token as Authorization: Bearer to the MCP server. On REST and WebSocket routes it goes in ?token=, so keep those URLs out of logs
2. Close sessions as soon as the work is done. Browser time bills one unit per 30 seconds, rounded up, idle or not
3. For multi-step work with browserless_agent, set keepSessionAlive: true on the first call and pass the returned sessionId after that. Sessions are one-shot by default since server 1.33.0
4. On 429, back off and retry. It means the plan's concurrency limit or queue is full, usually from sessions left open
5. Match the path to the protocol. Use /chromium for CDP clients and /chromium/playwright only for playwright.connect()

Selenium

1. Install with pip install selenium (Python 3.10 or later) and let Selenium Manager fetch drivers. Do not set driver paths
2. Use WebDriverWait with expected conditions, never fixed sleeps, and do not mix implicit and explicit waits
3. Set SE_AVOID_STATS=true to stop Selenium Manager sending usage statistics
4. Point coding agents at https://www.selenium.dev/llms.txt. Most Selenium 2 and 3 era examples use removed APIs
5. Set --username and --password before exposing a Grid beyond localhost. Check http://localhost:4444/status before creating sessions