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Free SEO developer tools Tools

Headers, source, JSON, regex, encoders and tech lookup. 9 free tools, no sign-up.

HTTP Header Checker Fetch any public URL and view its full HTTP response headers after redirects, with plain explanations of the SEO, caching and security headers. Live check HTML Source Code Viewer Fetch the raw HTML of any public page before JavaScript runs, with line numbers, search, a head-only view and download. Live check JSON Formatter & Validator Validate, beautify or minify JSON and JSON-LD, find syntax errors by line and column, sort keys and explore the data as a tree. In your browser XML & Sitemap Formatter Check that XML is well-formed, pretty-print or minify it, and count its elements, which is ideal for sitemaps, RSS and product feeds. In your browser Regex Tester for SEO Test regular expressions against your URLs or search queries with live highlighting, and start from ready-made Search Console, GA4 and redirect patterns. In your browser URL Encoder & Decoder Percent-encode or decode URLs and URL components, compare full-URL and component encoding, and break any URL into its parts and parameters. In your browser HTML Entity Encoder & Decoder Encode text and special characters as named or numeric HTML entities, or decode entities back into readable text. In your browser URL List Cleaner Clean a pasted URL list: trim, deduplicate, remove fragments and tracking parameters, force https, normalize slashes, extract domains and sort. In your browser Website Technology Checker See which CMS, store platform, frameworks, CDN, server and SEO plugins a public site uses, with platform-specific SEO tips. Live check

About seo developer tools tools

These utilities help with the small technical jobs that come up during audits, migrations and implementation. The HTTP header checker and HTML source viewer show exactly what a crawler receives from a public URL before JavaScript runs. The JSON and XML formatters check that structured data, sitemaps and feeds are well-formed.

The regex tester includes ready-made patterns for Search Console and GA4 filters with RE2 notes, and the encoders and URL list cleaner prepare data for redirect maps, spreadsheets and reports. The formatters, regex tester, encoders and cleaner run in your browser, so pasted code and lists stay on your device.

Frequently asked questions

Why view the raw HTML instead of the browser's Elements panel?

The Elements panel shows the page after JavaScript has run and changed it. The raw HTML is what the server sends first. Google can render JavaScript, but key tags such as titles, canonicals, robots meta and links are safest in the initial HTML, so comparing the two can reveal rendering problems.

What regex syntax does Google Search Console use?

Search Console regex filters use Google's RE2 syntax. RE2 does not support lookaheads, lookbehinds or backreferences, so patterns copied from other tools may fail. Test patterns against sample queries or URLs first and keep them as simple as possible. GA4 regex conditions also use RE2.

Is my code or data sent to a server?

The JSON formatter, XML formatter, regex tester, URL and HTML encoders and URL list cleaner run entirely in your browser, so what you paste stays on your device. The HTTP header checker and HTML source viewer fetch public URLs from our server, as a crawler would.