Screaming Frog
Desktop-based crawler capable of rendering JavaScript for deep SEO audits.
Next.js SEO Plugin
Next.js plugin to handle SEO metadata efficiently within React applications.
WWJD – What Would JavaScript Do?
Tool by Onely to visually compare a page with and without JavaScript.
TL;DR – Too Long; Didn’t Render
Tool by Onely that measures JavaScript rendering cost on a page.
You Might Not Need JQuery
At the very least, make sure you know what jQuery is doing for you, and what it's not.
View Rendered Source
A lightweight Chrome Extension that shows you how the browser has constructed (rendered) a page's original HTML into a functioning DOM, including modifications made by JavaScript.
RSC Playground
Dan Abramov's RSC Playground is a neat little visualiser to demonstrate how some of the tech around server components renders.
Sitebulb Response vs Rendered Report
Identify JavaScript SEO issues at scale using the Response vs Render report to spot template-level rendering problems and see exactly what search engines and LLMs can access. Detect indexing risks early, including missing canonicals or meta robots directives injected via JavaScript. Use Single Page Analysis to inspect individual URLs, and flag links that rely on JavaScript, ensuring internal link equity is passed through HTML, not client-side execution.
Rendering Difference Engine
The tool from The Grey Company immediately highlights discrepancies between response HTML and rendered HTML for any page. It groups and reports findings based on the key SEO elements that impact how Google crawls, understands, and indexes URLs.
Audisto JavaScript Crawler
Retrospective debugging with complete HTML, resource and JS console log storage. Analyze rendering issues and track DOM or content changes.