Local-first API intelligence

Find the API.
Trust the payload.

Monitor API contract drift, identify the request that powers a page, and turn captured JSON into a reusable extraction recipe—inside Chrome DevTools.

Install freeExplore features
✓ Generous free tier✓ Ollama stays local✓ No account required
Contract Guardian● CAPTURING
TrafficContractsAPI FinderPayload Lab · PRO
BEST MATCH · 96% CONFIDENCE

GET /api/v2/deals

20-item object array at $.data.deals matched visible products and expected fields.

{
  "title": "Launch fast",
  "price": 49,
  "image": "..."
}
CONTRACT DRIFT ◆ RESPONSE SHAPE ◆ API DISCOVERY ◆ PAYLOAD EXTRACTION ◆ LOCAL AI
One DevTools panel

From mysterious request to usable data.

Guardian connects the endpoint, response structure, visible page values, and extraction path.

01

Catch contract drift

Baseline JSON schemas locally and surface removed fields, type changes, and safe additions.

02

Find page data APIs

Rank first-party candidates by arrays, fields, visible values, and response shape.

03

Explore every path

Select a JSON path, expand nested fields, preview rows, and export a recipe.

Start useful

A free version worth keeping.

Core monitoring and API discovery remain free. Pro unlocks the payload-to-scraper workflow.

Free

$0

  • ✓ Fetch and XHR capture
  • ✓ Contract baselines and drift
  • ✓ Deterministic API ranking
  • ✓ API Finder with local Ollama
  • ✓ Optional cloud AI providers
Install free
Payload Lab Pro

Launch pricing

  • ✓ Complete response inspection
  • ✓ Exhaustive JSON path browser
  • ✓ Extraction recipe builder
  • ✓ Live row preview
  • ✓ CSV, JS, JSON, and Loompath export
Get a Pro license
Up and running

Open DevTools. Capture. Investigate.

Install Guardian, open its DevTools panel, and reload the page. Nothing is injected into the website.

  1. Install the extension. Add Guardian from the Chrome Web Store or load the unpacked release.
  2. Open Contract Guardian. Open DevTools on the target page and select the Guardian panel.
  3. Reload and investigate. Inspect traffic, ask API Finder, or send a JSON response to Payload Lab.