Search Engine Optimization (SEO)

A helpful checklist / collection of Search Engine Optimization (SEO) tips and techniques.

URL
Accessibility
Meta Information
Keywords
Content
Images
Videos
Links
Mobile
Sitemap
Social Media
Tools & Services
Books
Courses

URL

Descriptive URLs: Use a descriptive page url, which should reflect your targeted keyword.
File extension - Do not strip out the file extension on URLs.
HTTPS - Security is a top priority for Google.
Hyphens - Split words using hyphens.
Localisation - Choose a country-specific domain, for better local search results.
Subdomain or subfolder - Subdomains are seen as separate domains.
URL builder - Use this tool to add custom campaign parameters to your URLs.

Accessibility

403: Provide a 403 - Access denied page.
404: Provide a 404 - Page not found page.
Custom Search - With Google Sitelink search box, people can reach your content more quickly.
File not found: Avoid 404 FILE_NOT_FOUND errors.
Layout: Use divs instead of tables for layout. Using tables is not semantically correct.
Moving a website: Redirect all your links to the new location via .htaccess.
Pagination - Implement the rel="next" and rel="prev" attributes to links.
Performance - Performance and loading time is important.
Redirects: Avoid redirects if possible. Use 301 redirect instead of 302.
RichSnippets - Markup your code with rich snippets, they show up on the search results page.
Robots - Block pages which should not be indexed via the robots.txt file or <meta name="robots" content="">.
Validation: Write valid code (HTML Validator CSS Validator).
WAI-Aria - Use WAI-Aria tags to help machines understand your code.

Meta Information

Description - Each page should have a unique description (max. 160 characters) <meta name="description" content="">.
Title: Each page should have a unique speaking title (60 - 100 characters) <title>Website Title</title>.

Keywords

Content: Keyword should appear in ~3% of article length.
Heading: Keyword should appear in headings.
Meta Tag - You can ommit the <meta name="keywords" content="">, search engines do not use this meta tag.
Research: Rank for keywords with high traffic and less competition.
Single: Every page should have a single unique targeted keyword.
Title: Keyword should appear in page title.
URL - Keyword should appear in URL name.

Content

Content: Content matters the most in SEO.
Flash: Avoid Flash content and Flash pages. They are not accessible on mobile phones and will be ranked lower.
Freshness: New content is important. Updating pages or posting regularly is recommended.
Headings: Clear structure H1 -H6 max. 70 characters long.
Length: Article should be at least 300 words.
Strong: Use strong tag to highlight your targeted keyword.
Uniqueness - Do not provide duplicated content, use unique content types.

Images

Alt tag - Add an alt-tag this a description of the image (60 - 70 characters).
Dimensions: Add the width="" and height="" attributes to the image.
File name - Use a short descriptive name.
Optimization - Optimize images by removing some meta information.
Responsive Images - Serve the most optimized image corresponding to the window size.
Size: keep the filesize as low as possible.

Videos

Controls: Add controls to playback and control your video.
Embed: Allow others to embed your videos.
Transcriptions: Use transcriptions for indexing, usability & content.
Unplayable content - Avoid unplayable video content. Use HTML5 <video> tag instead of Flash.

Mobile

AppLinks - Apps that link to your content can then use this metadata to deep-link into your app.
mobile friendly - Mobile optimized sites are marked in search results. Test for mobile friendly site.
Smart App Banner - Safari has a Smart App Banner feature that provides a standardized method of promoting apps on the App Store from a website.
Tap targets - Clickable links should not be too small.
Viewport: Tell browsers how to adjust the page's dimensions and scaling to suit the device <meta name="viewport" content="width=device-width, initial-scale=1">

Sitemap

HTML sitemap - A HTML sitemap allows site visitors to easily navigate a website.
Image sitemap - Increase that your images can be found in Image Search results.
Mobile sitemap - For feature phones, you can create a mobile sitemap.
Video sitemap - Make sure, search engines know about all the video content on your site.
XML sitemap - Help search engines to index your pages.

Social Media

Authorship information.
Facebook - Sharing Best Practices for Websites & Mobile Apps.
OpenGraph - The Open Graph protocol enables any web page to become a rich object in a social graph.
Social Profiles - Add social profiles to your Google search results.
Social Shares: Provide sharing options for your site.
Twitter - With Twitter cards, you can attach photos, videos and media experience to you Tweets.

Tools & Services

Webmasters

Bing Webmasters - Allows webmasters to add their websites to the Bing index crawler.
Google Search Console (GWT) - Allows webmasters to check indexing status and optimize visibility of their websites.
Google Tag Manager - Learn about Google Analytics Tag Manager and how it can help simplify your life and need for IT requests. Launch new tags with a few clicks.

Analytics

Ahrefs - Analyze websites, track social media, build backlinks - Ahrefs has you covered. Try our marketing and SEO tools Site Explorer and Content Explorer today!
BuzzSumo - Find the most shared content for any topic or domain.
Followerwonk - Tools for Twitter Analytics, Bio Search and More.
Google Analytics - Generate detailed statistics about a website's traffic.
Open Site Explorer - Use Open Site Explorer to identify link building opportunities. Research backlinks, identify top pages, view social activity, and analyze anchor text.
Matomo - An open analytics platform.
SEMrush - SEMrush is a powerful and versatile competitive intelligence suite for online marketing, from SEO and PPC to social media and video advertising research.
Seomator - SEO Audit Tool and website crawler for SEO performance improving with How-to-Fix tips.
SEOstats - SEOstats is a powerful open source PHP library to request a bunch of SEO relevant metrics.
SimilarWeb - Compare website traffic with SimilarWeb.com's advanced traffic estimator tool. See any website's traffic sources & uncover their online marketing strategies.
SpyFu - Unlimited searches of any competitor's keywords for SEO or Google Ads. Research keywords, and find any domain's strongest content and their most dominant ad copy.
Twitter Analytics - Measure and boost your impact on Twitter.
Plausible - Simple and privacy-friendly alternative to Google Analytics.

Optimization

Web.dev - Get the web's modern capabilities on your own sites and apps with useful guidance and analysis from Web.dev. Whether you already have a website or you're just getting started, learn to build for the modern web at Web.dev.
PageSpeed Insights - Page Speed Insights measures the performance of a page for mobile devices and desktop devices.
Varvy Seo tool - Displays: domain strength, links, image seo, social counts & mentions, page/technical seo, pagespeed and more.
Webpagetest.org - Web Page Test gives you an overall performance waterfall as well as rendering timeline for sites. It also provides critical insight into time to first byte and what could be holding back web page performance.
WooRank - WooRank will help you to address issues on your site & identify opportunities to push you ahead of the competition.
Awesometechstack.com - AwesomeTechStack provides insights into the security, modernity, and performance of any website's technology stack and guidance to improve web vitals and the technology stack.

Keywords

Google Trends - Explore Google trending search topics with Google Trends.
Keyword Planner - Plan your Search Network campaigns and learn what your customers are looking for.
Keyword Tool - Best FREE alternative to Google Keyword Tool for SEO & PPC keyword research! Get 750+ relevant long-tail keywords from Google Suggest in seconds!
Moz Keyword Explorer - Paid Keyword Tool that provides precise search volume, keyword difficulty, SERP Features and organic click through rate data.
Keyword Clarity - Free keyword analytics tool that allows you to visualize and group keyword metrics with tree diagrams. The tool works with data from the Google Search Console API and CSVs.
SEOwl - Track your keyword rankings overtime and monitor your backlinks

Structured Data

Facebook Debugger - Enter the URL you want to scrape to see how the page's markup appears to Facebook.
Pinterest - Validate your Rich Pins and apply to get them on Pinterest.
Structured Data Testing Tool - Paste in your rich snippets or url to test it.
Twitter card validator - Enter the URL of the page with the meta tags to validate.

Bookmarklets

OuiSEO - An open-source bookmarklet that shows you on-page SEO and social meta data information.
SEO Bookmarklet - A One-Stop SEO Bookmarklet to Quickly Review On-Site SEO.

Browser Extensions

MozBar - The SEO Toolbar from Moz gives you quick access to many on-page SEO factors, Domain & Page Authority plus a quick nofollow toggle. Download the Free Toolbar today!

Jekyll Plugins

Jekyll SEO Tag - A Jekyll plugin to add metadata tags for search engines and social networks to better index and display your site's content.

TYPO3 Extensions

Basic SEO Features - Adds a separate field for the title-tag per page, easy and SEO-friendly keywords and description editing in a new module as well as a flexible Google Sitemap.
Google sitemap - High performance Google sitemap implementation that avoids typical errors by other similar extensions.

WordPress Plugins

All in One SEO Pack - The most downloaded plugin for WordPress (almost 30 million downloads). Use All in One SEO Pack to automatically optimize your site for Search Engines.
Yoast SEO - Improve your WordPress SEO: Write better content and have a fully optimized WordPress site using Yoast SEO plugin.
Slim SEO - Automated SEO tasks for you with a lightweight WordPress SEO plugin.