Common SEO mistakes are technical, content or strategy problems that stop Google from crawling, indexing or ranking a site well: a robots.txt file that blocks pages, a noindex left on after a redesign, duplicate content without a canonical, identical title tags or bought backlinks.
Which ones actually cost you traffic, and where should you start?
In this guide, you’ll learn:
- the 20 SEO mistakes to avoid that we find most often in audits, grouped by type
- what Google’s own documentation says about each one, with sources
- the myths to drop: minimum word counts, the 60-character title limit, the duplicate content penalty
- the order in which to fix these SEO errors
SEO mistakes that block indexing
These technical SEO issues come first, because a page has to be crawled and then indexed before it can rank, whatever the quality of its content. An SEO audit finds them quickly with a crawler like Screaming Frog and the indexing reports in Search Console.
1. Blocking Google with robots.txt
The robots.txt file controls crawling; indexing is handled elsewhere. An overly broad Disallow rule can stop Googlebot from crawling an entire folder, such as the whole blog or every product page. And blocking a page in robots.txt won’t take it out of search results: Google’s robots.txt documentation says it “is not a mechanism for keeping a web page out of Google” and tells you to “block indexing with noindex or password-protect the page.”
2. Leaving noindex on after a redesign
This is the most expensive SEO mistake we see after a redesign or migration. During development, the staging site is often set to noindex, and the setting sometimes stays on at launch. The damage can show up within days or weeks: pages drop out of the index and organic traffic falls sharply. Check the meta robots tag on your key pages and the Pages report in Search Console on launch day.
3. Changing URLs without 301 redirects
Every old URL left without a redirect returns a 404 error, and the backlinks that pointed to it lose their value. For URL changes, Google recommends server-side permanent redirects, 301 or 308. Its site move documentation also warns against two traps: redirect chains, which add latency, and redirecting many old URLs to the home page, which “might be treated as a soft 404 error.”
4. Filling the XML sitemap with junk URLs
An XML sitemap tells Google which URLs you want indexed. When it lists 404 pages, redirected URLs, noindex pages or duplicates, it sends mixed signals. Keep only canonical pages that return a 200 status code, then submit the file in Search Console.
5. Leaving broken internal links
A broken internal link sends visitors to a 404 error and cuts the path Googlebot follows to crawl your site. Broken links usually appear after a redesign, product removals or a change in URL structure. A monthly crawl catches them: fix the link at the source rather than stacking more redirects.
Title, meta description, heading and alt text mistakes
Title tags, meta descriptions and headings help Google understand a page and shape how it appears in search results. These SEO errors are easy to fix, but they often affect hundreds of pages at once.
6. Repeating the same title tag everywhere
Identical title tags on every page, like “Home” or just the company name, make it harder for users and search engines to tell pages apart. Google’s title link documentation asks for “distinct text that describes the content of the page” on each page, and says title link generation is “completely automated.” There’s no official 60-character limit either: the title link “is truncated in Google Search results as needed, typically to fit the device width.” Put the most important words first.
7. Neglecting the meta description
The meta description works on click-through rate rather than rankings. Google’s snippet documentation says it “may also use descriptive information in the meta description element when it describes the page better than other parts of the content,” and asks for descriptions that “accurately describe the specific page.” A blank description, or one copied across the whole site, gives Google no better summary than a passage it picks from your text.
8. Choosing heading levels by size
Headings structure the page for visitors, screen readers and search engines. The common mistake is choosing an H2 or H3 for its size on screen rather than its place in the outline. One H1 that states the topic, H2s for the main sections and H3s for subsections: that simple outline also makes a long page easier to scan.
9. Forgetting image alt text
Alt text describes an image for screen readers and for Google Images. Two mistakes come up again and again: images with no alt text at all, and alt text stuffed with keywords that have nothing to do with the picture. Describe what the image shows, and include the keyword only if it fits naturally.
Content mistakes that hurt SEO
Content is still the main lever in search engine optimization, and it’s also where most SEO myths live. Here are the content mistakes that hold rankings back, with what Google Search Central says about each.
10. Duplicate content without a canonical
Some duplicate content is normal on most sites: URLs with and without parameters, filtered pages, near-identical product pages. Google’s canonicalization documentation says it’s “not a violation of Google’s spam policies.” So there’s no penalty, but Google picks the canonical URL itself, and it may not be the page you want to rank. Point to the right version with a canonical tag or a redirect, especially on an ecommerce store where filters multiply URLs.
11. Writing to hit a word count
There’s no minimum word count for ranking. In its guide to helpful content, Google lists this as a warning sign: “Are you writing to a particular word count because you’ve heard or read that Google has a preferred word count? (No, we don’t.)” A page should be as long as the topic requires: a few lines for a definition, thousands of words for a complete guide. Padding a page mostly hurts the user experience.
12. Keyword stuffing
Keyword stuffing is part of Google’s spam policies: “filling a web page with keywords or numbers in an attempt to manipulate rankings in Google Search results.” Repeating the same phrase in every sentence mostly makes the copy harder to read. Use variations, synonyms and the vocabulary of the topic instead, the way an expert would explain it to a client.
13. Publishing near-identical pages at scale
Generating dozens of near-identical pages, one per city or per keyword variation, can fall under what Google calls scaled content abuse: “when many pages are generated for the primary purpose of manipulating search rankings and not helping users.” Google applies this policy however the content is made, with AI content tools or by hand. A page per city makes sense only when it adds real local information.
14. Ignoring search intent
Choosing a keyword for its volume, without checking what searchers want, can bring traffic that doesn’t convert. Before you target a query, look at the first page of Google to see what ranks: blog posts, service pages or product pages. Also make sure only one of your pages targets each query: keyword cannibalization puts your own pages in competition and can weaken them. More specific long-tail keywords are often the best starting point for a newer site.
Mobile and page speed SEO mistakes
Google indexes the mobile version of your site and measures real visitor experience with Core Web Vitals. Two mistakes come up often in this group.
15. Hiding content on mobile
Under mobile-first indexing, “Google uses the mobile version of a site’s content, crawled with the smartphone agent, for indexing and ranking,” according to its mobile-first indexing documentation. Text, sections or structured data removed from mobile to lighten the page disappear for Google too. The documentation says: “Make sure that your mobile site contains the same content as your desktop site.”
16. Still measuring FID instead of INP
Many audits and guides still cite FID, but INP (Interaction to Next Paint) replaced it among the Core Web Vitals on March 12, 2024. The current Core Web Vitals targets are an LCP within 2.5 seconds, an INP under 200 milliseconds and a CLS under 0.1. Check your field data in PageSpeed Insights and the Core Web Vitals report in Search Console: heavy images, third-party scripts and a slow server often explain page speed problems.
Link building and local SEO mistakes
Backlinks and the Google Business Profile carry real weight in organic and local rankings, and they’re also where shortcuts can backfire.
17. Buying backlinks for rankings
Google’s spam policies list buying or selling links for ranking purposes, excessive link exchanges and links with optimized anchor text in articles or press releases distributed on other sites as link spam. Domain Authority (DA) is a Moz metric that Google doesn’t use: a high-DA site can still be a link farm. Judge a backlink by the site’s topic, its real audience and the context around your brand, and skip the shortcuts we tested in our review of article submission sites.
18. Mismanaging your local business listing
For a local business, the Google Business Profile is the foundation of visibility in Google Maps. The usual local SEO mistakes: the wrong primary category, outdated hours, a name, address and phone number (NAP) that differ from one site to another and customer reviews left unanswered. Google’s Business Profile guidelines also state: “Including unnecessary information in your business name isn’t permitted, and could result in the suspension of your Business Profile.”
SEO strategy and tracking mistakes
The last two mistakes won’t show up in any crawler, but they decide whether search engine optimization produces business results.
19. Tracking rankings instead of conversions
A ranking is worth the calls and sales it brings. Track clicks, impressions and the pages gaining or losing organic traffic in Search Console, then use Google Analytics to tie organic traffic to conversions: contact requests, calls, sales. That tracking helps show which SEO mistakes to fix first.
20. Chasing special optimizations for AI Overviews
Many businesses think appearing in Google’s AI Overviews takes special tags or files. Google’s AI features documentation is clear: “There are no additional requirements to appear in AI Overviews or AI Mode, nor other special optimizations necessary.” The basics stay the same: an indexable page, clear content and verifiable facts. Those basics are also what our GEO agency works on for ChatGPT, Perplexity and other AI assistants.
In what order should you fix SEO mistakes?
Some SEO mistakes weigh far more than others: a robots.txt file that blocks the site comes before hundreds of missing alt texts. We sort fixes into four priority levels, from most urgent to least.
- What blocks crawling or indexing: robots.txt, noindex, missing redirects, server errors.
- What affects a whole template: duplicate title tags, a misconfigured canonical tag, an incomplete mobile version.
- What affects your key pages: search intent, content, internal links to the pages that bring in customers.
- Everything else: alt text, secondary meta descriptions, small optimizations.
Also plan a check before and after every redesign, migration or URL structure change: that’s when many technical SEO issues appear.
Getting your SEO mistakes fixed
SEO Montreal starts every mandate by analyzing your site and ranking mistakes by impact, then our team applies the fixes directly to your site. Our case studies show what that work produced in several industries, and our SEO pricing page explains how a monthly mandate is built.
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FAQ: common SEO mistakes
What are the most common SEO mistakes?
The most common SEO mistakes are a robots.txt file or noindex tag blocking pages, URL changes without 301 redirects, duplicate title tags, duplicate content without a canonical URL, an incomplete mobile version, keyword stuffing and bought or spammy backlinks. In audits, indexing problems after a redesign are the ones that cost the most organic traffic.
Does duplicate content cause a Google penalty?
No. Google states that some duplicate content on a site is normal and isn’t a violation of its spam policies. The real risk is elsewhere: the search engine picks the canonical URL itself among the duplicates, sometimes a different page from the one you want to rank. A canonical tag or a 301 redirect tells it which version to use. Copying content from other sites at scale is a different matter.
How many words does a page need to rank?
The right length is whatever fully answers the search intent. In its guide to helpful content, Google lists writing to a preferred word count as a warning sign, adding that it has no such preference. Compare how completely you cover the topic with the pages already ranking on page one, then add what the reader is actually missing.
Do title tags need to stay under 60 characters?
Titles can run past 60 characters: according to Google’s documentation, the title link is truncated as needed, typically to fit the device width. Google also sometimes generates a different title from the page content. Put the main topic first, keep the text unique and descriptive for each page, then check in Search Console whether the page’s click-through rate improves.
How do I find SEO mistakes on my site?
Start with Search Console: the Pages report lists URLs that aren’t indexed and why, and the Core Web Vitals report flags slow pages. A crawler like Screaming Frog then finds broken links, redirect chains, duplicate title tags and noindex pages. A full SEO audit adds a review of content, backlinks and search intent to show which fixes matter most.
How long does it take to fix SEO mistakes?
A robots.txt error or a leftover noindex takes minutes to fix, but Google then needs to recrawl the pages, which can take a few days to a few weeks. Content and link building fixes take longer to show in rankings. Search Console lets you request indexing for your most important pages once the fix is live.
Are technical SEO mistakes worse than content mistakes?
They’re more urgent, because one technical error can keep an entire section of the site out of the index. Once crawling and indexing are sorted, content becomes the main lever again: an indexed page that answers search intent poorly will still rank poorly. A good plan fixes blocking issues first, then improves the pages that bring in customers.
Should I run an SEO audit after a redesign?
Yes, ideally both before and after launch. A redesign is when many of the most serious mistakes happen: noindex left on, URLs changed without 301 redirects, content removed from the mobile version, broken internal links. Map every old URL to its new one and watch the indexing reports in Search Console for several weeks after launch.
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