CheckSEOFull-Site OverviewsOn-Page SEOTechnical SEODomain & NetworkStructured DataSocial SharingDeveloper UtilitiesYouTube ToolsAll 84 tools
Free SEO tools — meta tags, headings, images, keywords, and a full site audit. No signup.
CheckSEOFree SEO tools to check, audit, and fix your website
CheckSEO is a collection of 84 free tools for website owners, developers, marketers, and YouTube creators. Paste a URL and see exactly what search engines see: your title and meta tags, heading structure, image alt text, canonical and hreflang tags, redirects, robots.txt, sitemap, Core Web Vitals, structured data, and security headers. Every check explains what it found, why it matters, and how to fix it.
There is no signup and no paywall on any tool. The Full Site Audit runs the on-page and technical checks together and gives you one score to start from; the individual tools let you dig into a single issue. Alongside the tools, the blog has in-depth guides written by the developer who built them.
Browse tools by category
Full-Site Overviews
Run every check at once and get one score to start from.
6 tools
On-Page SEO
Title tags, headings, images, and content — what search engines read first.
10 tools
Technical SEO
Redirects, sitemaps, and crawl rules — the plumbing search engines depend on.
17 tools
Domain & Network
DNS, certificates, headers, and registration — what's true about a domain before any page loads.
7 tools
Structured Data
Generate the JSON-LD markup search engines use for rich results.
8 tools
Social Sharing
How your links actually look when they're shared.
5 tools
Developer Utilities
General-purpose tools that don't need a URL at all.
15 tools
YouTube Tools
For creators — no API key, no login.
16 tools
Latest SEO guides
All guidesSocial Media Character Limits 2026: Instagram, X, Threads, LinkedIn, Facebook, TikTok
Instagram caption character limit is 2,200, but the feed cuts it far sooner. Every 2026 limit for X, Threads, LinkedIn, Facebook and TikTok in one table.
6 min read
Social Media Image Sizes 2026: Every Dimension in One Cheat Sheet
Social media image sizes for 2026, checked against official help pages: Instagram, Facebook, X, LinkedIn, TikTok, YouTube and Pinterest, with safe zones.
6 min read
What Is a JWT? How to Decode a JSON Web Token (and What Never to Put in One)
JWT online decoder guide: what a JSON Web Token is, how to decode its header and payload, how to read exp and iat, and what never to put in one.
7 min read
"Alternate Page With Proper Canonical Tag" in Search Console: What It Means and When to Fix It
Alternate page with proper canonical tag in Search Console usually needs no fix. Learn to read it, spot a wrong canonical, and check the canonical chain.
6 min read
Hreflang Tags: The Complete Setup Guide (With the Return-Link Mistake Everyone Makes)
Hreflang tags explained: syntax, x-default, language and region codes, sitemap and HTTP header setup, and the missing return link that makes Google ignore them.
6 min read
Flesch-Kincaid Readability Explained: What Score to Aim For (and Why It's Not Everything)
Flesch-Kincaid readability explained: how Reading Ease and Grade Level work, a worked example, what score to aim for, and why the score isn't everything.
6 min read