Search Engine Ranking Factors

Contents:

  1. Introduction to Ranking Factors
  2. Contributors
  3. Most Important Factors
  4. In-Document Factors Affecting Ranking (31)
  5. Site Factors Affecting the Value of Hosted Documents (23)
  6. Factors Affecting the Value of a Link (25)
  7. URL, Technical, Hosting & Server Side Factors (12)
  8. Detrimental Ranking Factors (12)

Introduction to Ranking Factors

This article contains a large list of the factors that can influence a web document's rank at the major search engines (Yahoo!, MSN, Google & AskJeeves) for a particular term or phrase. Although it is impossible to say for certain which of these items affects which search engine or how important the factors are individually, I've created an estimated ranking importance scale as indicated by the following symbols:

/ Exceptional Importance
These factors have primary influence in ranking search results at the major search engines.
/ High Importance
These factors have a high impact on modifying rankings of web documents in the SERPs.
/ Moderate Importance
These factors have a measurable level of affect on the rankings in the SERPs, but are not major contributors.
/ Slight Importance
These factors carry some impact on rankings and could be important when in a highly competitive area.
/ Inconsequential Importance
These factors are of low consequence in changing the ranking positions of a web document. They may have some effect in certain queries or documents.

For each factor, the 13 individuals (myself and 12 others in the field) voted on each factor's perceived importance. I then averaged these votes to come up with the scores you see listed next to the factors. In addition, the standard deviance (which measures how much fluctuation existed between votes) is also listed and a scale has been created to show if there was wide disagreement or general consensus on a factor's importance.

/ Highly Disputed
These factors have a wide variance of opinion on importance.
/ Somewhat Disputed
These factors have some dispute as to their importance.
/ Average Agreement
These factors have an average level of dispute/consensus.
/ Some Consensus
These factors have some consensus on importance levels.
/ High Consensus
These factors have a high level of consensus.

The factors listed herein provide a near-comprehensive list of factors which can positively or negatively influence the rank of a web document. If you have questions or would like to contribute additional ideas, please e-mail me.

List of Contributors

The following individuals made this project possible by submitting their opinions on each ranking factor, and adding comments where they felt it important. I have taken note of many of these comments in my description of the ranking factors and each score is representative of the group's overall opinions. Many thanks to:

Danny Sullivan /
Dan Thies /
EGOL / Profile @ SEOmoz
Graywolf /
Jill Whalen /
Donna Fontenot /
Michael Martinez /
Bill Slawski /
Ammon Johns /
Scottie Claiborne /
2K /
Todd Malicoat /
Rand Fishkin / My votes are also included in the avgs

Most Important Factors

The following are the top 10 ranked factors across the 5 categories:

  1. Title Tag - 4.57
  2. Anchor Text of Links - 4.46
  3. Keyword Use in Document Text - 4.38
  4. Accessibility of Document - 4.3
  5. Links to Document from Site-Internal Pages - 4.15
  6. Primary Subject Matter of Site - 4.00
  7. External Links to Linking Pages - 3.92
  8. Link Popularity of Site in Topical Community - 3.77
  9. Global Link Popularity of Site - 3.69
  10. Keyword Spamming - 3.69

In-Document (on-page) Factors Affecting Ranking:

The following factors are on-page items that affect the ranking directly by virtue of being a part of the indexed and retrieved document. Many of these factors will not apply universally to all documents, while others are standard.

Hide contributor comments
Factor Name / Description
/ / Title Tag
Avg 4.57 | Std. Dev. 1.12 / Denoted by the <title> tags in HTML, this tag always shows at the top of a browser window and often appears in the SERPs as the title of the web page.
Bill Slawski
In addition to the value of a title tag when a search engine determining what a page is about, people will often use the title of a page when choosing anchor text to link to the page.
Michael Martinez
Should be unique for each page on the site. Use for branding a company name as secondary content is okay.
Scottie Claiborne
Critical to ranking well.
Todd Malicoat
Also very important for those engines that track click through rates for natural SERPS.
/ / Keyword Use in Document Text
Avg 4.38 | Std. Dev. 1.00 / The use of queried terms (the keywords users search for) appearing in the document text.
Bill Slawski
While it isn't completely essential to have keywords appearing in the text of a document (search for "click here"), it certainly can help to have those words appear on the document.
Michael Martinez
Establish relevance through on-page factors where practical.
/ / Links to Document from Site-Internal Pages
Avg 4.15 | Std. Dev. 0.95 / A specific page's importance in a site's overall architecture can be measured by the the importance and depth of the other pages on on the site that refer to the page in question. An internally well-linked to document is generally considered more important than an obscured or buried page.
Bill Slawski
It can be tempting to relate number of links to a page with the number of valuable links to a page, but a page on a site linked to by the three most important pages on a site may be more important than another page linked to by hundreds of other pages.
Danny Sullivan
Disagree with this (RAND: Note, the above description has been changed since Danny's comment)
Scottie Claiborne
This is a factor the site owner has total control over and should utilize internal linking to enhance relevance.
Todd Malicoat
Easily the most underrated criteria by web developers everywhere. Getting the proper ratios of keyword anchor text with both internal and external links is crucial to good rankings.
/ / Uniqueness of Document Text
Avg 3.38 | Std. Dev. 0.92 / A document's unique elements are what is generally looked at by the search engines and if the unique elements of a document (the body text or content) is an exact copy of another document (whether that document is on your site or on another), that page's value will often be deeply discounted or even removed from the listings.
Bill Slawski
There may be more than one way of looking at duplicate content by the search engines. For instance, a mirror site may be ignored completely and not indexed, while very similar content may be indexed but filtered, and not served at the time of a query.
Scottie Claiborne
This may come into play in the future more than currently.
Todd Malicoat
Have thoroughly tested this, but my gut says if you beat the dupe filters you're probably going to be in okay shape.
/ / Related Term Use in Document Text
Avg 3.31 | Std. Dev. 1.06 / Along with the actual targeted term/phrase, search engines examine all of the text in a document to determine if the other terms used are related and whether they give the subject of the document a specific slant as related to the primary subject.
Bill Slawski
Global text similarities probably play a larger role here than the description you have implies, and similarities between documents can be helpful in defining the primary subject of a document. See Salton, et al, in Automatic structuring of text files.
Dan Thies
likely to have an influence, in link analysis, use of related terms may help w/ topical factors
Scottie Claiborne
It's a good idea and tends to happen naturally when writing
Todd Malicoat
I would almost argue that this is more important than exact terms in the document text, though both are very important
/ / External Links in Document
Avg 3.08 | Std. Dev. 1.14 / The sites and pages linked to from a document. These may positively or negatively influence rankings based on the quality of the links, their relationship to the linking document and any existing relationships between the sites hosting the documents.
Michael Martinez
Remove references to "quality". It's become an over-abused SEO buzzword.
Scottie Claiborne
We know analysis of external links happens when linking out.
Todd Malicoat
While relationships are important the actual ANCHOR TEXT is extremely important as well. Linking to documents with the anchor text of the phrases you are targeting for a specific page is quite helpful (though it may negatively impact visitor retention rate).
/ / Age of Document
Avg 2.77 | Std. Dev. 0.97 / Nearly every document has an "inception date" calculated by a search engine as the first time the spider noticed the page or a link to the page. Older documents may be considered more "authoritative", "trusted" and "valuable" than new documents, particularly if they have continued to build links over a long period of time. New documents may be considered more "timely" or "relevant" to time-sensitive queries.
Danny Sullivan
I think fresh documents these days might get a boost, but ironically old pages might also get a boost probably through looking at history of links. So no idea which way to go on this!
DazzlinDonna
Especially important to Google
Scottie Claiborne
I think the age of the domain may be more critical than the age of a specific document on that domain
Todd Malicoat
Definitely one of the hardest variables to manipulate. I think G is going overboard on it lately.
/ / Citation Links or Sources
Avg 2.77 | Std. Dev. 1.19 / Citations (as footnotes or endontes in a research paper) could be links to additional info or mentions of publications, documents or papers from which information was drawn. This factor may be more prevalent in queries focused on academic or scholarly-type searches.
Scottie Claiborne
I'm not sure the difference between this factor and the outgoing links described earlier.
Todd Malicoat
There's definitely different values to different links. This is a trend that will continue. May qualify as a 3 now, but I think link quality will fall under much heavier scrutiny, thus giving it a 4 in the future.
/ / Stemming & Plurality Evaluation
Avg 2.39 | Std. Dev. 0.74 / Terms used on a page or in a query may be considered the same or only related by search engines. If a term is stemmed to its root form (i.e. financing & finance to financ) it could be that anchor text, queries, etc. containg that term would be equivalent & interchangeable.
Michael Martinez
The meaning of "...would all provide equivalent value" is unclear. (RAND: Changed to make greater sense)
/ / Meta Description Tag
Avg 2.39 | Std. Dev. 1.21 / The meta description tag is almost completely outdated in markup, but is still useful for describing your page accurately to the search engines. In some cases, the engines may even use this tag as the description of your site in the results page listings, giving you greater control over your content and message. It is questionable, however, that keyword use in this tag has any influence, whatsoever, in affecting the rankings.
Danny Sullivan
but very important in terms of helping control a description, rather than ranking, in the right circumstances
Michael Martinez
Keyword use should be used where they stimulate user interest.
Scottie Claiborne
More important for getting people to click than for getting high rankings.
/ / High Level Authorship Marks
Avg 2.38 | Std. Dev. 1.21 / These are structural signs that a piece of content is of great merit. Although we may not be aware of all the factors that fit into determining a document's quality through automated analysis, it is presumed by many that the major search engines have invested time and effort to find automated systems to measure a document's relative quality.
Danny Sullivan
I think this is better said (RAND: Updated to make clearer)
EGOL
Examples would be a H1, H2, H3 hierarchy in headings/subheadings, ordered lists, quotations/citations, onpage anchor links.... USED IN CONCERT. If you want to see "high level authorship marks" look at this document...
Todd Malicoat
Hand edits are definitely a reality. Definitely important, but the prevalence will most likely always be fairly small compared to the overall size of the web due to it's sheer magnitude.
/ / Organization of Document Text
Avg 2.31 | Std. Dev. 1.26 / In certain documents, particularly those with lengthy content and an obvious hierarchy or structure, the ordering of words, phrases, sentences and concepts can be taken into account by search engines.
Bill Slawski
Sequence, proximity, and adjacency of words are important, but a global analysis of similar documents is probably a step taken long before an onpage analysis.
EGOL
Very little impact if we are talking about word order... but add a little HTML formatting such as headings, bold, ordered lists, onpage anchor links, and organization then becomes very important.
Michael Martinez
Organization that survives linearization is best.
Scottie Claiborne
I believe the page contents are analyzed as a document without regard to what is first vs what is last.
/ / Text in Alt/Img Title Tags
Avg 2.23 | Std. Dev. 0.97 / The use of text in alt tags and image tags is figured into the overall text in a document, although it probably does not undergo the scrutiny of body text in terms of quality, grammar, reading level, etc. Both of these tags are more commonly used for targeting image searches at the engines, along with the filenames of the images shown.
DazzlinDonna
Sometimes helpful for secondary terms
Jill Whalen
Very important for clickable images. Not so much for non-clickable ones.
Scottie Claiborne
Only in images that are links. Images that are not links typically show no change when adding alt text however for link images, it replaces the anchor text and as such, is very important.
Todd Malicoat
Alt text is actually important for using as repetitive anchor text for images. For instance the alt text of an image.
/ / Paragraph Headings
Avg 2.23 | Std. Dev. 1.12 / Paragraph headings, either through Hx tags or simply through formatting may give detailed on-page emphasis to the topic of a page and demonstrate that multiple aspects of a topic are discussed - if the topics of these headings are diverse yet still clustered tightly around a theme, it may be beneficial.
Bill Slawski
Attempting to understand a theme of a document (without looking at other documents) based upon paragraph headings, especially based upon layout without the use of heading elements, is probably not much of a relevance factor.
DazzlinDonna
Can be very important for less competitive terms.
/ / Variety & % of Content Changes
Avg 2.23 | Std. Dev. 1.19 / Along with measuring historical and current rates of change, search engines watch for the amount of content that has changed in a document over the course of updates and which specific pieces of content on a web page have experienced change. For example, cosmetic changes (to color or fonts) may be ignored along with changes to every document on a site (during, for example, a template update). What search engines want to measure is documents that "keep up with the times" by adding new content and changing or removing old content that becomes invalid over time.
2K
This is heavily linked to (internal and external) link data.
Bill Slawski
It's difficult to assign a value to this factor. Under the historic data patent from Google that this factor appears to be taken from, amount and type of change may be more important for some queries than others. For instance, a query for the "1998 superbowl"...
Scottie Claiborne
I don't see that this specifically affects rankings as much as it may change what the page ranks for. Any time you change page text, it will have an affect on the rankings.
/ / Document Language
Avg 2.15 | Std. Dev. 0.95 / For obvious reasons, a document's language matching the query term and the user's location (by IP address or engine version used, i.e. google.de, yahoo.jp, etc.) is significant in making a document rank well.
Danny Sullivan
much higher if you are using a country-specific service, otherwise, nope
/ / Keyword Use in URL
Avg 2.15 | Std. Dev. 1.02 / Using the keyword term/phrase in the actual URL of the document may be assigned some weight by search engines, whether used in hyphenation or strung together.
Dan Thies
people use the URL in links, don't they?
DazzlinDonna
Works better for non-Google search engines
EGOL
Probably does not help a lot if the KW is in your filename. However, IMO, owning the KW.com is kickass for rankings and SERP clickthrough.
Michael Martinez
Hyphenated keywords seem to work better.
Scottie Claiborne
Minor and only in play if people link to the page using the page URL.
Todd Malicoat
It is actually important by default. If someone links to your site using the URL, you have the keywords in anchor text rather than just a variable or arbitrary name.
/ / Meta Keywords Tag
Avg 2.08 | Std. Dev. 0.9 / Although largely a remnant of the early days of web markup, the meta keywords tag is still used by search engines as a reference point for the terms targeted by the page. It can be of value to place common misspellings of your primary targets, if any, into this tag.
DazzlinDonna
Can be more important in distinguishing a spammy site than anything else.
Scottie Claiborne
If it plays a role in ranking for misspellings, than it plays a role, period. You can't say it works for misspelled words but not for others. Personally, I don't believe it works for misspellings. I believe Google's habit of suggesting a correction for a misspelling or semantic analysis is more likely to be the source of "misspelled" traffic than including the misspellings in the meta keywords tag.