CheckSEO Blog
Practical SEO guides, tied to the tool that lets you check your own site — no fluff, no signup.
Social 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.
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.
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.
"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.
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.
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.
Open Graph Tags: The 6 You Need, the Sizes That Work, and How to Debug Previews
Open Graph tags explained: the 6 og: tags every page needs, og:image sizes for each platform, and how to fix stale previews on Facebook, LinkedIn and WhatsApp.
Custom 404 Pages: What a Good One Does, With Examples and the SEO Rules
A custom 404 page must return a real 404 status, not 200. The SEO rules, soft 404s, what to include, examples, and setup for Nginx, Apache and Next.js.
AI Crawlers Explained: GPTBot, ClaudeBot, PerplexityBot and Whether to Block Them
AI crawlers explained: GPTBot, ClaudeBot, PerplexityBot and more, grouped by training, search and user fetches, with robots.txt rules to block or allow each.
Meta Description Length in 2026: Pixel Limits, Not Character Counts
Meta description length explained: Google truncates at about 920 pixels, roughly 155–160 characters on desktop and 120 on mobile. How to write and preview it.
FAQ Schema: How to Add It, What Google Changed, and Whether It Still Helps
FAQ schema explained: Google stopped showing FAQ rich results on 7 May 2026. Get the FAQPage JSON-LD template, the rules, and whether to keep the markup.
HTTP Security Headers Checklist: The 7 Headers Every Site Should Send
Security headers checklist: the 7 headers every site needs, what each one blocks, and copy-paste config for Nginx, Apache, Next.js on Vercel and Cloudflare.
SPF, DKIM and DMARC Explained: Fix Email Deliverability in One Afternoon
SPF, DKIM and DMARC explained in plain English, with copyable TXT records for Google Workspace and Microsoft 365 and a safe p=none to p=reject rollout.
Reverse DNS Lookup: What PTR Records Are and How to Check Yours
Reverse DNS lookup explained: what a PTR record is, why mail servers demand one, how to read dig -x output, and how to get a PTR set at common hosts.
What Are UTM Parameters? A Practical Guide With Naming Conventions
What are UTM parameters? The five tags, what GA4 does with each, a naming convention that stops split reports, and the internal-link mistake that breaks attribution.
Regex Cheat Sheet: Every Pattern You Actually Use, With Live Examples
Regex cheat sheet you can scan: anchors, classes, quantifiers, groups, lookarounds and flags — plus the 8 patterns people actually paste, ready to test.
How to Find Your YouTube Channel ID (and Any Other Channel's) in 30 Seconds
How to find a YouTube channel ID three ways: YouTube Studio, the page source, or a handle-to-ID finder. Plus why the @handle is not the channel ID.
Do Hashtags Work on YouTube? What They Do, Where to Put Them, and the 3-Hashtag Rule
Do hashtags work on YouTube? Yes, but not like Instagram. The 60-hashtag limit that voids the whole set, where to place them, and what #shorts does now.
YouTube Thumbnail Size: The Exact Dimensions, Ratio, and File Limits
YouTube thumbnail size is now 3840×2160 px (16:9), JPG or PNG, up to 50 MB from a computer or 2 MB from a phone. Full spec, Shorts, and the safe zone.
How Much Does YouTube Pay Per View? Real RPM Numbers by Niche
YouTube pays most creators $0.001–$0.005 per view ($1–$5 per 1,000), far more in finance and far less on Shorts. See real RPM ranges by niche, CPM vs RPM, worked examples, and what it takes to get paid at all.
YouTube Tags: Do They Still Matter, and How to Write Them
YouTube says tags play a 'minimal role' — so what are they still good for? Learn the 500-character limit, the three jobs tags still do, a copyable template, and the mistakes that can get a video removed.
Why Your Favicon Isn't Showing in Google Search (and How to Fix It)
A missing search favicon doesn't throw an error — it just quietly shows a generic globe icon. See Google's actual favicon requirements and check your own page free.
Free Meta Tag Generator: Build Title, Description & OG Tags in Seconds
Writing meta tags by hand usually means the social tags get forgotten entirely. See what a generator actually outputs and build your own set free, no signup.
Twitter/X Card Validator: Why Your Links Preview Wrong (and How to Fix It)
A link can look perfect on Facebook and render as plain text on X. See why Twitter Cards are a separate system from Open Graph, and validate your own link free.
How to Check What CMS Any Website Is Running On
Most CMS platforms leave fingerprints in a page's own HTML — file paths, script URLs, meta tags. See how to spot them, and check any site free, no signup.
How Old Is a Domain, and Does It Actually Matter for SEO?
Domain age itself isn't a ranking factor, despite what most SEO advice implies. See what actually correlates with it, and check any domain's real age free.
8 Screaming Frog Alternatives (Including Free, No-Install Options)
Screaming Frog's free tier covers 500 URLs — here's what to reach for past that, including tools that need no install at all. See the real tradeoffs, free.
7 Free Ahrefs Alternatives That Actually Work in 2026
No free tool replaces Ahrefs' backlink index — but plenty replace its site-audit function completely. See exactly which half of the job each free tool covers.
Free Internal Linking Audit: Find Orphan Pages and Weak Anchor Text
Internal links do two jobs: help pages get discovered, and tell Google what a page is about through anchor text. Audit both on your own site, free.
301 vs. 302 Redirects: Which One Actually Protects Your Rankings
A 301 and a 302 send a visitor to the exact same place — but only one tells Google to transfer your ranking signals. See which to use when, free checker included.
Free SEO Report Template (Built From What a Real Audit Tool Outputs)
An SEO report has one job — let someone who didn't do the work understand what changed. See the 5 sections a report actually needs, with a worked example.
Duplicate Content and SEO: What Actually Counts, and What Doesn't
Duplicate content doesn't get your site "penalized" the way most people think. See what Google actually does with it, the real causes, and a free checker to compare two pages.
Is Your Site Mobile-Friendly? What Google Actually Checks
Google's own mobile-friendly test still trips up sites that look fine to the eye. See what actually gets checked — viewport, tap targets, text size — and test yours free.
Broken Links: Why They Pile Up, and How to Find Them Before Visitors Do
Broken links accumulate quietly as a site grows and pages move. See why they hurt more than you'd think, and scan your own page free for dead links.
How to Validate Your XML Sitemap (and Fix the Errors Google Actually Cares About)
Validate your XML sitemap in seconds. See the 7 most common sitemap errors that block Google from crawling your pages, and exactly how to fix each one — free, no signup.
6 Robots.txt Mistakes That Can Quietly Deindex Your Site
One wrong line in robots.txt can deindex your entire site. See the most dangerous robots.txt mistakes and test yours free with CheckSEO's Robots.txt Checker.
What Is Keyword Density, and How Much Is Actually Too Much?
Keyword density isn't the ranking factor most people think it is. The real formula, healthy ranges by content type, and a free checker to test your own page.
The Full SEO Audit Checklist: Every Check That Actually Matters
A full SEO audit isn't one test — it's dozens run together. See exactly what technical, on-page, content, and site-health checks a real audit covers, and run them all free in one pass.
Heading Structure and SEO: How H1–H6 Hierarchy Actually Works
A broken heading hierarchy confuses both readers and search engines. See the most common H1-H6 mistakes and check your own page's structure free, no signup.
What Are Meta Tags, and Which Ones Actually Affect SEO?
Not all meta tags matter for SEO. See which ones actually affect rankings and click-through rate, the most common mistakes, and a free analyzer for your own page.
Image Alt Text: What It's For, and How to Write It Right
Alt text isn't just an SEO checkbox — it's what screen readers rely on and what shows when an image fails to load. See the mistakes that break it and check your own page free.
What Is a Website Health Score, and What Does It Actually Measure?
A website health score condenses dozens of technical, content, and security checks into one number. See what actually goes into it and check your own site free.
Schema Markup Explained: What It Is and How to Generate It
Schema markup is what earns rich results in Google — star ratings, FAQ dropdowns, recipe cards. See how it works and generate valid JSON-LD for your page free.
Core Web Vitals Explained: LCP, CLS, and INP in Plain English
Core Web Vitals measure real loading speed, visual stability, and responsiveness — not vague "performance." See what each metric means and test your page free.