Check the speed and usability of your site on multiple devices
Enter a URL, and this tool will test the loading time and performance for desktop and for mobile, plus identify opportunities to improve (and pat you on the back for what you’re doing well). The mobile results also come with a user experience score, grading areas like tap targets and font sizes.
See how your local business looks online
Moz crunches data from more than 15 different sources—including Google, Foursquare, and Facebook—to score your brick-and-mortar business on how it looks online. Results come complete with actionable fixes for inconsistent or incomplete listings.
700+ keyword ideas based on a single keyword
Enter a keyword, and the Keyword Tool provides a huge handful of long-tail keyword opportunities, organized alphabetically.
Complete web stats and search insights
In addition to tracking pretty much every bit of traffic you could imagine on your website, Analytics also surfaces many keyword insights as to which terms people use to land on your pages.
Constant website analysis, alerts, and error reports
These webmaster tools help give you a taste of what the two top search engines think of your site. It’s helpful to see any bugs, alerts, and indexing issues.
Comprehensive link analysis
The free version of Open Site Explorer gives you a quick look a full range of link analysis, including a look at the most impactful links coming your way and your most linked-to pages.
Know what people search for
Enter a keyword or group of keywords into the tool, and Google will return all sorts of helpful stats to guide your keyword strategy: monthly search volume, competition, and even suggested terms you might not have considered.
8. Google.com in an Incognito Window
Discover auto-fill opportunities
Searching Google.com in an incognito window will bring up that all-familiar list of autofill options, many of which can help guide your keyword research. The incognito ensures that any customized search data Google stores when you’re signed in gets left out. Incognito may also be helpful to see where you truly rank on a results page for a certain term.
Changes in search volume for key terms
A quick browse or search through Google Trends can show you the hockey-stick rise of potential terms and SEO opportunities for your content.
Full analysis of your website
The QuickSprout tool does a comprehensive look at just about everything: SEO optimization, speed, tags, keywords, social, links, and even competitor comparisons.
11. Schema Creator
Uber-customize the way your search results appear
Create custom code so that your reviews, events, organizations, and people are displayed the way you want on search pages. Once you’ve created your schema code, copy and paste to your website, or try the free WordPress plugin for an even easier implementation.
Here’s an example of schema in action:
View site stats for any domain
Use this tool to compare traffic between two websites, a helpful tool for competitor research.
See where your site ranks for certain terms
You can run Rank Checker one of two ways: Input your keyword and your website and see where you land, or leave the website field blank to view the top-to-bottom list of results for a keyword.
14. XML Sitemaps Build a sitemap
Simply enter your site’s URL and some optional parameters, and XML Sitemaps will create a sitemap that you can upload to Google Webmaster Tools.
See your website the way a search engine sees it
Enter your site, and this tool will strip out everything but the guts, revealing your website the way search spiders see it. This particular view can be helpful to see the hierarchy you’ve given particular elements (maybe without realizing it!).
16. SEO Site Checkup
Audit and score for your website
Site Checkup runs through a fast audit of your site, checking for proper tags and surfacing any errors that might come up.
Performance dashboard for search and social rankings
The free version of the Searchmetrics report shows you a taste of how your website ranks in search and social, along with a preview of top terms.
18. Find Broken Links Discover errors on your site
The link report from Ninja Internet Marketers combs through your whole site and highlights a number of link insights, including the internal and external links that need fixing.
19. Ahrefs’ Site Explorer and Backlink Checker Complete overview of your website, pages, and links
A free (and substantial) sampling of what ahrefs offers, the dashboards for referring pages and inbound links are rich and informative.
Check for duplicate content
Enter a URL for a blogpost or website, and Copyscape can tell you where else that content exists online. You might find results that you’ll need to follow-up with to help get your SEO in order.
I’ve shied away from referencing any toolbars thus far, but the Moz toolbar is just too good to pass up. Once installed, the Moz toolbar can show you SEO insights from within Google search results pages and at any particular website.
Robots.txt files let the web robots know what to do with a website’s pages. When a page is disallowed in robots.txt, that’s instructions telling the robots to completely skip over those web pages. There are some exceptions in which case a robots.txt might be ignored, most notably malware robots that are looking for security issues.
Structured data helps to provide context to the information on your page. This tool from Google uses live data to validate the structured data for any web page, or you can copy/paste code to test it.
The Microsoft SEO Toolkit combines quite a few different tools into one. Used together, it can analyze your site and provide recommendations on how to make your site’s content more SEO- friendly, including tweaks to your sitemap and robots.txt. Sorry to all of the Apple folks, this one seems to be Windows-only!