There are many opinions within the SEO community. In many cases, some people believe that a particular approach helps or doesn’t help with gaining better rankings or more organic traffic from Google. However, there are very few definitive studies or insights available.
While there are hundreds of thousands of websites using a table of contents in most or all of their articles, there are many more that don’t. They probably have different reasons, but one obvious explanation is that they do not believe they help.
While we do not need to make the case of why a table of contents can benefit the user, I’ll share some of my findings in this insights article to make an SEO case.
Disclaimer: The sample size used in this test is below statistical significance, and I would advise you to run similar test(s) on your own website before drawing firm conclusions. The purpose of this experiment is to provide a starting point for further analysis, and I would love to hear about your own findings.
Hypothesis
One of my websites publishes short pieces of content (under 1,000 words) where I doubted the intrinsic value of a table of contents for the user. However, after several months of running the website and doing more competitor analysis, it was my hypothesis that because almost every competitor in the top ten used a table of contents, that it’s something Google would algorithmically expect to see because of their usage of comparison methods like champion lists.
I decided that it was worth testing adding a table of contents to articles over 600 words in length. While there would be minimal benefit to the user, it could be seen as a huge improvement to an algorithm. So I wanted to see if this would make a positive, negative, or neutral difference to either the existing rankings or the overall visibility of the page (total keywords, etc.)
Many people say that testing on live websites is impossible or shouldn’t be done, but when done right, sometimes with difficulty, it can give you strong insights into how to change and adapt your process. It’s the cornerstone of my own publishing model as part of what I call progressive optimization.
Success on this test would be observing a visibility improvement over a significant % of the total URLs from adding in a table of contents.
Method
- Find underperforming articles with stable rankings that were over six months old.
- Filter them to be the same type of article. In this case, list articles.
- The list articles had to have between 600-1,000 words in total.
- Other list articles that did not qualify for the above would be the control URLs.
- Manually add a table of contents with the shortcode option in the Table of Contents Plus plugin.
- Display the shortcode after the introduction, open by default, including H2 and H3 only.
- Make the change, clear the website cache & force-update with Google Search Console.
- Test the URLs individually and utilize a changelog in Google Sheets to monitor progress.
There were only a total of 15 pages that fit the word count criteria that were over six months old.
Existing traffic levels or rankings were not a concern because I only wanted to see whether there would be an improvement in visibility (impressions) or rankings (average position).
Findings
The findings were mindblowing because I regularly run tests on live websites. Getting anything over a 50% success rate is impressive, even with so few URLs in the test.
| Attempts | Successes | Success Percentage |
|---|---|---|
| 15 | 15 | 100% |
Every attempt improved the overall visibility and, in some cases, the rankings.
Quite often, an improvement in visibility can mean you were indexed for new search terms, which will usually decrease your average position on Google Search Console.
The increase was hugely visible in some cases, especially the overall impressions.
These articles had remained steady through Google’s May 2022 core update that ended on June 9th. This ruled out some possibility of external factors influencing the results, as did the emphatic number of successes. The control URLs saw nothing similar happen during the same time period.
The few above facts indicated that the result was not a mere correlation, with strong confidence for a live website.
Article #4 was massively underperforming for a well-written and researched article. It had only been receiving around 10 impressions per day on average for months. Adding a table of contents to the article increased that average to 210 per day.
Article #4 had a result that represented a daily visibility increase of 2000%.
Not all the tests were as emphatically successful as test #4, but all were successful enough to increase visibility by hundreds of percent each.
The overall findings were that adding a table of contents increased total visibility through a combination of improved rankings for existing terms and an increase of overall terms in the top 100.
The increase in total overall terms was far more pronounced than improved rankings on existing terms.
Conclusion
The success of these tests does not prove that a Table of Contents is a huge ranking factor. However, it does prove they can be one. The massive success of my own URLs should prove that the bid system exists and that missing out on an important ranking factor in that SERP (Search Engine Ranking Page) can hold back a decent article from performing as it should.
It vindicated my own hypothesis, which was valuable to me as an insight into how the website should be run as standard in the future. The table of contents would not benefit the user massively. Still, it would not harm them either, while giving a huge improvement to overall search performance when combined with my existing processes on the website.