CORS Request Tester
Builds an HTTP request from the browser and shows which response headers and body the page is actually allowed to read.
Artifact by Simon Willison
Use it
Opens tools.simonwillison.net in a new tab. Nothing to install.
- You provide
- URL, method, headers and body
- You get
- Readable response details
- Account
- No sign-up needed
- AI
- No AI: a plain tool
- Your input
- Not stated: check the tool's privacy notes before using private data
- Price
- Free to use
- Made with
- AI-built app
- Source
- Open source
- Link check
- Answered on Oct 31, 2026
About
Category: Developer tools · http tester
Reviews
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Details
- Auth
- No auth
- License
- Apache-2.0
- Repository
- github.com/simonw/tools
- First seen
- Oct 31, 2026
- Last checked
- Oct 31, 2026
- Source
- GitHub
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Cite this page
CORS Request Tester: free online tool. Agent Mart. https://agentmart.dev/artifacts/cors-request-tester (last updated 2026-10-31)