DevSnoopDevSnoop

Command Reference

All 17 commands available through the DevSnoop HTTP API. Send JSON to localhost:9400 and get structured results back.

Base Request

Every command is a POST request to the same endpoint. Use tabID to target a specific tab (recommended), or omit it to use the active tab.

bash
curl -s -X POST http://127.0.0.1:9400/ \
  -H 'Content-Type: application/json' \
  -d '{"command":"<command>","params":{...},"tabID":<optional>}'

Tab Management

Page Inspection

Page Interactions

Debugging

Change Detection

Health Check

Workflows

Common multi-step patterns.

Inspect a page you're building

bash
# 1. Find the tab
curl -s -X POST http://127.0.0.1:9400/ \
  -d '{"command":"list_tabs","params":{}}'

# 2. Get page structure (use tabID from step 1)
curl -s -X POST http://127.0.0.1:9400/ \
  -d '{"command":"page_summary","params":{},"tabID":123}'

# 3. Check for errors
curl -s -X POST http://127.0.0.1:9400/ \
  -d '{"command":"get_logs","params":{"level":"error"},"tabID":123}'

Test a form interaction

bash
# 1. Find the input
curl -s -X POST http://127.0.0.1:9400/ \
  -d '{"command":"find","params":{"selector":"input"},"tabID":123}'

# 2. Fill it
curl -s -X POST http://127.0.0.1:9400/ \
  -d '{"command":"fill","params":{"selector":"#email","value":"test@test.com"},"tabID":123}'

# 3. Submit
curl -s -X POST http://127.0.0.1:9400/ \
  -d '{"command":"click","params":{"selector":"button[type=submit]"},"tabID":123}'

# 4. Check for errors
curl -s -X POST http://127.0.0.1:9400/ \
  -d '{"command":"get_logs","params":{"level":"error"},"tabID":123}'

Verify visual changes after code edits

bash
# 1. Take baseline snapshot
curl -s -X POST http://127.0.0.1:9400/ \
  -d '{"command":"diff","params":{},"tabID":123}'

# 2. Make code changes — page hot-reloads

# 3. Compare against baseline
curl -s -X POST http://127.0.0.1:9400/ \
  -d '{"command":"diff","params":{},"tabID":123}'

Tips

  • - Always use tabID when you know it — avoids depending on which tab is focused.
  • -page_summary is your starting point — it gives you selectors you can pass directly to click, fill, inspect_element, etc.
  • - Responses are intentionally compact and token-efficient. No raw HTML — just structured data.
  • -get_logs and get_network auto-attach the debugger on first call. Logs are buffered (200 entries max), so call early if you need to capture events.
  • -diff is useful after hot-reload — take a baseline, make changes, then compare.
  • - When you get a "Permission needed" error, the user needs to click the DevSnoop extension icon and grant access for that site. One-time per origin.