Important SEO Tools
For the SEO check you will need two tools that you should first install and configure.
Screaming Frog is a crawler that analyzes up to 500 pages in the free version. The various SEO elements are separated by tabs. With the filter functionality you can search for specific problems like duplicate, missing or too long/short tags.
Google Webmaster Tools
Update (29.5.2015): Google Webmaster Tools has a new name: Google Search Console. The functionalities are still the same.
SEO Check Step by Step
Tools: Screaming Frog (tab “URI”)
URLs should be human readable, so they should not consist of IDs or random characters.
Words in URLs should be separated by hyphens.
URLs should not exceed 200 characters in length.
2. Title Tags
Tools: Screaming Frog (tab “Page Titles”) and Google Webmaster Tools (“Search Appearance” > “HTML Improvements”)
Title tags should not be longer than 55 characters or they may be cropped.
Every page should have its own title tag. Keywords should be mentioned at the beginning of the title tag.
3. Meta Description Tags
Tools: Screaming Frog (tab “Meta Description”) and Google Webmaster Tools (“Search Appearance” > “HTML Improvements”)
Meta Descriptions should contain 150 to 160 characters and include keywords.
Make sure that at least your most important pages have unique meta descriptions. Ideally every page has a good meta description.
4. Content Structure
Tools: Screaming Frog (tab “H1”)
There should be exactly one H1 tag per page. To structure your content you are free to use H2 – H6 tags.
5. Internal Links
Tools: Google Webmaster Tools (“Search Traffic” > “Internal Links”)
Check if your most important pages are well linked internally. These should be placed in the navigation and/or footer.
Use keywords in anchor texts of internal links.
Tools: Screaming Frog (tab “Images”)
Every picture should have an ALT tag.
File names of images should describe its content and contain relevant keywords.
7. Page Speed
Google PageSpeed Insights analyzes your website’s speed. There are separate tests for mobile and desktop devices. Consider implementing the recommendations to speed up your website.
8. Source Code
W3C’s validator analyzes your source code for syntax errors. Try to keep your code as correct as possible. Try to eliminate as many errors as possible.
Tools: Google Webmaster Tools (“Search Traffic” > “Mobile Usability”)
As of April 21, 2015 websites that are not optimized for mobile devices will disappear from mobile search. Test your website with the Mobile-Friendly Check to see if your website is effected. Additionally, use Google Webmaster Tools’ “Mobile Usability” report to find any issues on mobile devices.
Tools: Google Webmaster Tools (“Crawl” > “Sitemaps”, “Crawl” > “robots.txt Tester”, “Google Index” > “Blocked Resources” and “Google Index” > “Index Status”)
Use a sitemap to tell the crawler which pages should be indexed.
Prevent admin pages or private pages from being indexed by adding them to the robots.txt. Check the robots.txt for errors.
Test if any necessary resources are blocked for crawlers.
Compare the number of pages that are indexed with your sitemap and the number of results found in Google.
11. Duplicate Content
Your website should be accessible either by http://www.yourdomain.com or http://yourdomain.com, but not both. Pick one version and redirect request to the other option via 301 redirects.
Make sure that your content is not accessible via multiple URLs. Siteliner is a web tool that can find duplicate content for you.
12. Broken Links
Tools: Screaming Frog (tab “URI”) and Google Webmaster Tools (“Crawl” > “Crawl Errors”)
Redirect (301) broken links (URIs with a status code of 404) to pages with similar content.
If you perform such an SEO check on a regular basis and eliminate errors found in the process, your website will stay well crawlable and indexed by search engines.