# [Search Engine Optimization (SEO)](//marcobiedermann.github.io/search-engine-optimization/)
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A helpful checklist / collection of Search Engine Optimization (SEO) tips and technics.
## Table of Contents
* [URL](#url)
* [Accessibility](#accessibility)
* [Meta Information](#meta-information)
* [Keywords](#keywords)
* [Content](#content)
* [Images](#images)
* [Videos](#videos)
* [Links](#links)
* [Mobile](#mobile)
* [Sitemap](#sitemap)
* [Social Media](#social-media)
* [Tools & Services](#tools--services)
* [Webmasters](#webmasters)
* [Analytics](#analytics)
* [Optimization](#optimization)
* [Keywords](#keywords-1)
* [Structured Data](#structured-data)
* [Bookmarklets](#bookmarklets)
* [Books](#books)
* [Courses](#courses)
## URL
* **Descriptive URLs:** use a descriptive page url, which should reflect your targeted keyword
* **[Subdomain or subfolder](//www.youtube.com/watch?v=_MswMYk05tk):** subdomains are seen as separate domains
* **[Hyphens](//www.youtube.com/watch?v=AQcSFsQyct8):** split words using hyphens
* **[www or no-www](//support.google.com/webmasters/answer/44231):** provide both domains, but set a prefered version in Google Webmaster Tools
* **[Localisation](//support.google.com/webmasters/answer/62399):** choose a country-specific domain, for better local search results
* **[HTTPS](//googlewebmastercentral.blogspot.be/2014/08/https-as-ranking-signal.html):** Security is a top priority for Google
* **[URL builder](//support.google.com/analytics/answer/1033867):** Use this tool to add custom compaign parameters to your URLs
* **[File extension](//www.youtube.com/watch?v=dSG6C33GwsE)**: do not strip out the file extension on URLs
## Accessibility
* **403:** provide a 403 - Access denied page
* **404:** provide a 404 - Page not found page
* **Robots:** block pages which should not be indexed via the `robots.txt` file or
``
* **File not found:** avoid `404 FILE_NOT_FOUND` errors
* **Redirects:** Avoid redirects if possible. Use 301 redirect instead of 302
* **[Pagination](//support.google.com/webmasters/answer/1663744):** implement the `rel="next"` and `rel="prev"` attributes to links
* **Moving a website:** redirect all your links to the new location via `.htaccess`
* **[Performance](//developers.google.com/webmasters/mobile-sites/mobile-seo/common-mistakes/slow-mobile-pages):** performance and loading time is important
* **Validation:** write valid code ([HTML Validator](//validator.w3.org/) [CSS Validator](//jigsaw.w3.org/css-validator/))
* **[WAI-Aria](//www.w3.org/TR/wai-aria/):** use WAI-Aria tags to help machines understanding your code
* **[RichSnippets](//schema.org/):** markup your code with rich snippets, they show up on the search results page
* **[Custom Search](//developers.google.com/structured-data/slsb-overview):** with sitelink Google Sitelink search box, people can reach your content more quickly
* **Layout:** Use `divs` instead of `tables` for layout. Using `tables` is semantically not correct.
## Meta Information
* **Title:** each page should have a unique speaking title (60 - 100 characters)
`
Website Title`
* **[Description](//www.youtube.com/watch?v=W4gr88oHb-k):** each page should have a unique description (max. 160 characters)
``
## Keywords
* **Single:** every page should have a single unique targeted keyword
* **Research:** rank for keywords with high traffic and less competition
* **[URL](//www.youtube.com/watch?v=rAWFv43qubI):** keyword should appear in URL name
* **Title:** keyword should appear in page title
* **Heading:** keyword should appear in headings
* **Content:** keyword should apear in ~3% of article length
* **[Meta Tag](//www.youtube.com/watch?v=jK7IPbnmvVU):** you can ommit the ``,
search engines do not use this meta tag
## Content
* **Content:** Content matters the most in SEO
* **Headings:** Clear structure `H1` -` H6` max. 70 characters long
* **Strong:** use `strong` tag to highlight your targeted keyword
* **[Uniqueness](//www.youtube.com/watch?v=mQZY7EmjbMA):** do not provide duplicated content, use unique content types
* **Length:** article should be at least 300 words
* **Freshness:** new content is important. Updating pages or regulary posting is recommended
* **Flash:** avoid Flash content and flash pages. They are not accessible on mobile phones and will be ranked lower
## Images
* **[File name](//www.youtube.com/watch?v=h2SWuUobbr0):** use a short descriptive name
* **[Alt tag](//support.google.com/webmasters/answer/114016):** add an alt-tag this a description of the image (60 - 70 characters)
* **Dimentions:** add the `width=""` and `height=""` attributes to the image
* **[Responsive Images](//www.w3.org/TR/html-picture-element/):** serve the most optimized image corresponding to the window size
* **Size:** keep the filesize as low as possible
* **[Optimization](//imageoptim.com/):** Optimize images by removing some meta information
## 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](//developers.google.com/webmasters/mobile-sites/mobile-seo/common-mistakes/unplayable-content):** Avoid unplayable video content. Use HTML5 `