SEO Audit Checklist: The 21 Checks and Where Real Sites Fail

The results split in a way I didn't fully expect. The technical basics were close to perfect across the board. Page speed was a wreck on nearly every site. And the median overall score was 87, which tells you how little a score says on its own. Here's the whole checklist, what each check really tests, and where real sites fail it.

What is an SEO audit, really?

There are two kinds. A consultant's deep dive crawls every URL and reads the backlink profile by hand. An automated audit runs a fixed set of measured tests on one URL in about a minute. They answer different questions.

Ours is the second kind. It checks one URL, usually the homepage, against 21 checks and rolls them into category scores and one overall number. If you want a tool roundup, see which free SEO tools are actually free. This post takes a real report apart line by line.

One honest limit before we start. An audit measures hygiene. It doesn't tell you where you rank, who outranks you, or whether anyone links to you. Rankings take a local rank tracker. Keep that in mind any time a score looks good.

Which SEO audit checks do real sites fail most?

Here's the whole board. These are the most recent audits on 19 sites: 15 client sites across home services, the trades and retail, plus four of our own properties. They ran between July 10 and September 14. Two of the sites wouldn't complete Google's PageSpeed test, so the five speed checks cover 17 sites, not 19.

Overall scores ran from 65 to 94. The median was 87, and 18 of the 19 sites scored 83 or higher.

Now read that next to the speed rows. A site can score in the high 80s and still take 15 seconds to show its main content on a phone. The score averages the good news with the bad, and the bad is what costs you visitors.

What do the technical SEO checks test?

• SSL certificate. HTTPS with a valid certificate. Browsers warn people away from sites without one.
• robots.txt. The file that tells crawlers what they're allowed to fetch. We check that it loads and doesn't shut the site out.
• XML sitemap. The list of URLs you want found. We check that it exists and count what's in it.
• Mobile responsive. A viewport meta tag, the minimum sign that the page was built with phones in mind.
• Canonical tag. The page's preferred address, so the same content on two URLs doesn't split its signals.
• Server response time. How quickly the server starts answering. Our slowest was 1,072 ms, which failed. Two others at 615 and 655 ms got a warning.

Why does almost everybody pass? Modern hosting and site builders ship most of this by default. That's good news. It's also why a technical score of 100 shouldn't make anyone feel finished.

The check that can still fool you here is the sitemap, and not because it's missing. Our own audit in July said our sitemap passed, with 1 URL in it. The file existed, so it passed. It was also close to useless. Today it lists 28 URLs, because we add every new page to it by hand, and in September we caught a post that had been left out. I told that story in the Bing IndexNow post. A pass means the file is there. Open it and read it.

What does an on-page SEO audit catch?

The meta description passed on only 8 of 19 sites, and the failures came in three shapes.

• Too long. Seven sites ran from 163 to 352 characters. Google trims long descriptions, so the end of your pitch never shows up.
• Too short. Three sites had 10, 22 and 87 characters. Ten characters isn't a description. It's a placeholder somebody forgot to replace.
• Missing. One site had none, which leaves Google to write your snippet from whatever text it finds on the page.

Title tags did better, passing on 15 of 19. Three ran long at 68 to 72 characters, and one page had no title tag at all. In my experience a long title is often the template's fault, not the owner's. Plenty of themes and SEO plugins tack the business name onto the end of every title, so a sensible 50 character headline ships at 70. Fix the template, not the headline.

Everything else in this group passed on 18 of 19. One site had two H1 headings. One had 2 of its 20 images without alt text. The missing schema and the missing social tags both came from the same site, the one that scored 65, which also had no title tag, no meta description and no canonical. When a site misses the basics, it tends to miss them all at once.

Why do so many sites fail the page speed checks?

This is the ugliest row on the board. Fourteen of the 17 sites were rated poor on LCP, somewhere between 4.4 and 15.3 seconds. The other three were close but still over the line at 2.6, 2.7 and 2.9 seconds. Not one passed.

First Contentful Paint, the moment anything at all shows up on screen, passed on 2 of 17. The mobile performance score passed on 3.

Two rows tell you where the problem isn't. Cumulative Layout Shift passed on all 17, so these pages aren't jumping around while they load. Total Blocking Time passed on 11, so most of them respond fine once they arrive. The pages are stable. They're just heavy. That usually comes down to pictures: a full size photo straight off a camera or a stock site, dropped into a hero section and served to a phone on a cell connection.

Most of these are good looking sites built by people who cared. The big beautiful image that sells the business is the same image that makes the page slow.

Our own site isn't exempt. KillerSEOx came in at 5.7 seconds on LCP in July, and that was the one red row on our report.

What does an AI readiness audit check?

AI crawler access passed on all 19. A site generally only fails this one if somebody went out of their way to block those bots, so a pass is the normal state.

llms.txt was on 16 of 19, and that number is high for a reason. Adding one is part of how we set up the sites we manage, so this row reflects our process more than the wider web, where the file is still rare. If you want the full walkthrough, the AIO on-page checklist covers llms.txt and entity schema step by step.

Structured data for AI passed on 13, and the misses were specific. Two sites had LocalBusiness schema and no FAQ schema. One had FAQ schema and no LocalBusiness. Two had other schema but neither type, and one had none at all.

Content depth passed on 16. Three homepages came in between 696 and 746 words, just under the 800 word line our audit uses. Treat that line as a nudge, not a law. A homepage that says clearly who you are, what you do and where you do it beats a padded one. For the bigger picture on why any of this matters, start with what AIO is and how AI visibility tracking works.

What did our own SEO audit find, and what did we fix?

I'd rather show you ours than only talk about everyone else's. On July 13 the audit gave killerseox.com an 87: technical 100, on-page 92, speed 74, security 100 and AI 73. Here's what happened to each red and yellow row, checked against the live site this morning.

• Meta description, 189 characters. Fixed. It's 160 today.
• Structured data for AI, no LocalBusiness or FAQ schema. Half fixed, on purpose. The homepage carries FAQ schema now. We didn't add LocalBusiness, because we're a software product sold nationwide, not a storefront. Adding a business type that doesn't describe us just to quiet a warning would be the wrong fix.
• Content depth, 746 words. The homepage has changed a lot since July. The next audit will tell us where it landed.
• First Contentful Paint at 2.1 seconds and a mobile score of 74. Warnings, and both tie back to the next row.
• Largest Contentful Paint, 5.7 seconds. The fail. Still open, and it's the one I care about most.

That list is the real lesson of any audit. Not every warning deserves a fix. The ones that matter change what a visitor actually experiences, and on almost every site we looked at, that's speed.

An audit is a list, though, and a list doesn't prioritize itself. Turning findings like these into ranked, weekly work is what our SEO action engine does. If you run audits for clients, I wrote up how we use one to open sales conversations in the 60-second close, and our white label SEO software puts your name on the report instead of ours.

Want to see which of these 21 rows your site passes? Run the free audit on your homepage, or start on the free tier and keep watching the numbers week to week. Then go open your sitemap and look at your hero image. Those two alone will tell you a lot.