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Webmaster Tools

About Webmaster Tools

A single place for the everyday checks that come up when you build, run or debug websites, APIs and email: 77 tools, one tab, no sign-up.

What's here

  • Inspect & debug: Webhooks, HTTP requests, signatures and CORS
  • DNS & domains: DNS records, propagation, WHOIS and IPs
  • Email: Deliverability, headers, SPF, DMARC and blocklists
  • SEO: Indexability, sitemaps, meta tags and redirects
  • Security: TLS, headers, CSP, cookies, tokens and hashes
  • JSON & data: JSON, JSONPath, YAML, XML, CSV and test data
  • Text & encoding: Encoding, case, slugs, Unicode, diff, Markdown
  • Dev utilities: Regex, cron, time zones, subnets and more
  • CSS & design: Colors, gradients, shadows and layout
  • Images: Resize, compress, favicons, PDF and QR codes

How it works

Formatters, converters, decoders and generators run in your browser. JSON, JWTs, passwords, hashes and the rest are processed by JavaScript on the page and are not sent to our server.

Network checks run on our server. DNS, WHOIS, SSL, redirects, headers, CORS, robots.txt, meta tags, email records and port scans need to reach the internet directly, so the server performs them and returns the results. Localhost, link-local and private network addresses are blocked for these checks, the request builder and webhook forwarding.

The webhook inspector gives you a URL that captures any request sent to it and streams it to your browser live. The last 100 requests per URL are kept in the server's memory and are cleared when the server restarts.

The AI assistant (the "Ask AI" button) can run the network checks for you and explain the results. It is powered by Claude, a model from Anthropic. Its answers can be wrong; check anything important with the tool pages it links to.

Privacy at a glance

No accounts, no advertising, no analytics trackers and no cookies. Preferences such as the anonymize toggle and which menu sections are open are stored in your own browser. The Privacy Policy covers the details.

Who runs it

This instance of Webmaster Tools is operated by Webmaster Tools. Questions, bug reports and requests: hello@webmastertools.dev.